www.mediit.in Complete Practice of NCERT for NEET 11& 12 ASTER THE CERT BIOLOGY-II Thousands of MCQs Based on Each & Every Topic of Latest NCERT Class-XII SANJAY SHARMA Co-authored by Sanubia Kavita Thareja ARIHANT PRAKASHAN (Series), MEERUT www.mediit.in Arihant Prakashan (Series), Meerut All Rights Reserved © Publisher No part of this publication may be re-produced, stored in a retrieval system or by any means, electronic, mechanical, photocopying, recording, scanning, web or otherwise without the written permission of the publisher. Arihant has obtained all the information in this book from the sources believed to be reliable and true. However, Arihant or its editors or authors or illustrators don’t take any responsibility for the absolute accuracy of any information published and the damage or loss suffered thereupon. All disputes subject to Meerut (UP) jurisdiction only. Administrative & Production Offices Regd. Office ‘Ramchhaya’ 4577/15, Agarwal Road, Darya Ganj, New Delhi -110002 Tele: 011- 47630600, 43518550 Head Office Kalindi, TP Nagar, Meerut (UP) - 250002 Tel: 0121-7156203, 7156204 Sales & Support Offices Agra, Ahmedabad, Bengaluru, Bareilly, Chennai, Delhi, Guwahati, Hyderabad, Jaipur, Jhansi, Kolkata, Lucknow, Nagpur & Pune. ISBN 978-93-24196-88-0 PO No : TXT-XX-XXXXXXX-X-XX Published by Arihant Publications (India) Ltd. For further information about the books published by Arihant, log on to www.arihantbooks.com or e-mail at info@arihantbooks.com Follow us on www.mediit.in PREFACE In the present dynamic scenario of competitions, NCERT Books are gaining importance day by day. On an average about 30% questions asked in various competitions are from NCERT. Similarly with the incorporation of Board weightage in competitions the necessity of dual synchronous preparation i.e., to study NCERT for School Exams and for Competitive Exams, is increasing day by day. Arihant’s Master the NCERT Series is framed with the philosophy of such synchronous preparation in mind. The book consists of 16 chapters, in each of which questions are framed on each & every line of NCERT text. Some special features of Master the NCERT books which make these books stand apart from other NCERT based books are — Each chapter has a NEET Key Notes for quick revision of whole NCERT content. — Each chapter has topically divided objective questions based on NCERT content to cover all the topics of NCERT text. — Separate section in each chapter having special types questions for NEET. — Complete coverage of NCERT Exemplar objective questions in each chapter. — Detailed explanations for selected questions. — Appendix given at the end contains some Important Multicolored Diagrams from the whole NCERT curriculum. The variety in types of questions framed will be helpful in analysis of self-performance and exposures to face tough problems of competitions. Previous Years' Medical Entrance Questions have also been incorporated at appropriate places so that the students get the exposure of type of questions asked in various competitions on the same topic. Huge efforts have been made from our side to keep this book error free, but inspite of that if any error or whatsoever is skipped in the book then that is purely incidental, apology for the same, please write to us about that so that it can be corrected in the further edition of the book. Suggestions for further improvement of the book will also be welcomed & incorporated in further editions. Publisher www.mediit.in CONTENTS 1. REPRODUCTION IN ORGANISMS 1-18 NEET Key Notes 1-4 Mastering NCERT with MCQs — Lifespan and Asexual Reproduction — Sexual Reproduction 4-6 7-9 NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 2. SEXUAL REPRODUCTION IN FLOWERING PLANTS 9-12 13-14 15-18 19-44 NEET Key Notes 19-23 — Mastering NCERT with MCQs Flower and Development of Gametes — Pollination — Double Fertilisation and Development of Endosperm — Embryo, Seed and Fruit Formation — Apomixis and Polyembryony 24-28 28-30 30-31 31-32 33 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 33-37 37-38 39-44 3. HUMAN REPRODUCTION 45-71 NEET Key Notes 45-49 Mastering NCERT with MCQs — Male Reproductive System — Female Reproductive System — Gametogenesis — Menstrual Cycle — Fertilisation and Implantation — Pregnancy and Embryonic Development — Parturition and Lactation 50-51 51-52 53-54 54-56 57-58 58-59 59 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 60-64 64-65 66-71 4. REPRODUCTIVE HEALTH 72-90 NEET Key Notes Mastering NCERT with MCQs Reproductive Health-Problems and Strategies — 72-74 75 www.mediit.in ASTER THE CERT BIOLOGY-II — — — Population Stabilisation and Birth Control Medical Termination of Pregnancy and Sexually Transmitted Infections Infertility NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 5. PRINCIPLES OF INHERITANCE AND VARIATION NEET Key Notes Class-XII 75-77 77-78 78-79 79-84 84-85 85-90 91-123 91-96 Mastering NCERT with MCQs — Mendel's Laws of Inheritance — Inheritance of One Gene — Inheritance of Two Genes — Polygenic Inheritance and Pleiotropy — Sex-Determination — Mutation — Genetic Disorders 97 97-100 100-102 102 103 103 104-106 NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 107-112 112-113 114-123 6. MOLECULAR BASIS OF INHERITANCE 124-160 NEET Key Notes 124-130 — Mastering NCERT with MCQs The DNA — The Search for Genetic Material and RNA World — Replication — Transcription — Genetic Code — Translation — Regulation of Gene Expression — Human Genome Project (HGP) — DNA Fingerprinting 131-133 133-134 134-135 136-137 138-139 139-140 140-141 142 143 NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 144-149 150-151 152-160 7. EVOLUTION 161-188 NEET Key Notes 161-164 Mastering NCERT with MCQs — Origin of Life and Evolution of Life Forms 165-166 www.mediit.in ASTER THE CERT BIOLOGY-II — — — — — — Evidences of Evolution Adaptive Radiation Biological Evolution and its Mechanism Hardy-Weinberg Principle A Brief Account of Evolution Origin and Evolution of Man NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 8. HUMAN HEALTH AND DISEASES Class-XII 166-168 168-169 169-170 170-172 172-173 173 174-179 180-181 182-188 189-218 NEET Key Notes 189-195 — Mastering NCERT with MCQs Human Health and Common Diseases in Humans — Immunity — AIDS (Acquired Immuno Deficiency Syndrome) — Cancer — Drug and Alcohol Abuse 195-198 198-201 202 203 204-205 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 206-209 210-211 212-218 9. STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION 219-241 NEET Key Notes 219-223 Mastering NCERT with MCQs — Animal Husbandry, Management of Farms and Farm Animals — Animal Breeding, Bee-keeping and Fisheries — Plant Breeding and Single Cell Protein — Tissue Culture 223-224 224-226 226-229 229-230 NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 230-234 235-236 237-241 10. MICROBES IN HUMAN WELFARE 242-260 NEET Key Notes 242-244 Mastering NCERT with MCQs — Basic Concepts and Microbes in Household Products — Microbes in Industrial Products — Microbes in Sewage Treatment 245-246 246-247 247-248 www.mediit.in ASTER THE CERT BIOLOGY-II — — Microbes in Production of Biogas Microbes as Biocontrol Agents and Biofertilisers NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 11. BIOTECHNOLOGY : PRINCIPLES AND PROCESSES Class-XII 249 249-250 251-254 254-256 256-260 261-283 NEET Key Notes 261-265 Mastering NCERT with MCQs — Principles of Biotechnology and Restriction Enzymes — Cloning Vectors and Competent Host — Processes of Recombinant DNA Technology — Bioreactors and Downstream Processing 266-269 269-270 271-272 272-273 NEET Special Types Questions NCERT Exemplar Questions Answers & Explanations 273-277 277-278 279-283 12. BIOTECHNOLOGY AND ITS APPLICATIONS 284-302 NEET Key Notes 284-286 Mastering NCERT with MCQs — Biotechnological Applications in Agriculture — Biotechnological Applications in Medicine — Transgenic Animals — Ethical Issues 287-288 289-290 290-291 291 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 292-296 296-297 298-302 13. ORGANISMS AND POPULATION 303-334 NEET Key Notes 303-308 Mastering NCERT with MCQs — Organism and its Environment — Population Attributes — Population Interactions 308-312 313-316 316-319 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 319-324 324-325 326-334 www.mediit.in ASTER THE CERT BIOLOGY-II Class-XII 14. ECOSYSTEM 335-364 NEET Key Notes 335-339 Mastering NCERT with MCQs — Ecosystem-Structure and Function, Productivity and Decomposition — Energy Flow and Food Chain — Ecological Pyramids — Ecological Succession — Nutrient Cycling and Ecosystem Services 339-341 341-344 345-346 347-348 348-349 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 350-355 355-356 357-364 15. BIODIVERSITY AND CONSERVATION 365-383 NEET Key Notes 365-368 Mastering NCERT with MCQs — Biodiversity : Levels and Patterns — Importance and Loss of Biodiversity — Conservation of Biodiversity 368-370 371 372-373 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 374-377 377-378 379-383 16. ENVIRONMENTAL ISSUES 384-408 NEET Key Notes 384-388 Mastering NCERT with MCQs — Air Pollution and its Control Measures — Water Pollution and its Control Measures — Solid Wastes, Agrochemicals and Radioactive Wastes — Greenhouse Effect, Global Warming and Ozone Depletion — Improper Resource Utilisation and Deforestation 389-390 391-392 392-393 393-394 394-395 NEET Special Types Questions NCERT & NCERT Exemplar Questions Answers & Explanations 396-401 402-403 404-408 Some Important Diagrams of NCERT (Multicolored Diagrams) 1-8 www.mediit.in CHAPTER 01 > Reproduction in Organisms 1 CHAPTER > 01 Reproduction in Organisms NEET KEY NOTES Å The period from birth to the natural death of an organism represents its lifespan. Whatever be the lifespan, death of every individual organism is a certainty, i.e. no individual is immortal, except single-celled organisms. Å Reproduction is a vital biological process by which living organisms produce new individuals of their own species. It enables continuity of species. Reproduction is of two types asexual and sexual. Asexual Reproduction Å Å Å Å Å It involves the participation of a single parent to produce an offspring. As a result, the offspring produced are morphologically and genetically similar to one another and also to their parents and can be referred to as clones. The unit of reproduction is commonly formed from the somatic cells of the parent. Meiosis does not occur in asexual reproduction. Asexual reproduction is common among single-celled organisms and in plants and animals with relatively simpler body organisation. Cell division itself is a mode of reproduction in protists, e.g. Amoeba and monerans. In bacteria, the parent cell divides into two to give rise to new individuals. It may take place by following methods Asexual Reproduction Fission Budding Binary Parent body divides into two daughter individuals, e.g. Amoeba. Multiple Parent body divides into many daughter individuals, e.g. Plasmodium. Å External An outgrowth (bud) formed on the parent body constricts and separates to form a new organism, e.g. Hydra, yeast. Internal Small, gemmules (internal buds) form new individuals, e.g. Spongilla (sponge). Spore formation Fragmentation Spores are propagules which germinate to produce new individuals, e.g. fungi. Breaking of parent body into fragments and each fragment develops into a new organism, e.g. Spirogyra. Regeneration Formation of the whole body of an organism from a small fragment or by replacement of the lost body part, e.g. sponge and Planaria. During unfavourable conditions, the products of multiple fission become individually surrounded by resistant coats, i.e. cyst (encystation) and gets released, once favourable condition arises sporulation occurs. It is seen in Amoeba. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 2 Å In Monera, Protista, Fungi and Algae, spores formed can be of following main types Pseudopodiospore (with fine pseudopodia) – Amoeba Zoospores (motile and flagellated) – Chlamydomonas and Ulothrix Conidia (non-motile) – Penicillium n Sexual Reproduction Å In sexual reproduction, there is formation of male and female gametes either by same individual or by different individuals of opposite sex. These gametes fuse to form a new cell called zygote, e.g. occurs in all flowering plants, humans, etc. Å The period of growth from birth up to the reproductive maturity in an organism is called as juvenile phase. In plants, this period of growth starting from seed germination up to initiation of flowering is called vegetative phase. Å The later phase, when the organisms start reproducing sexually, is called reproductive phase. The end of reproductive phase is marked by the onset of another phase called senescent phase which is the last phase in life cycle after which the organism dies. Å A few plants exhibit unusual flowering phenomenon; some of them such as bamboo species flower only once in their lifetime, generally after 50-100 years, produce large number of fruits and die. Another plant, Strobilanthes kunthiana (Neelakurinji), flowers once in 12 years. Å In non-primate mammals like cows, sheep, rats, deers, dogs, tigers, etc., the cyclical changes during reproduction are called oestrous cycle whereas in primates (monkeys, apes and humans) it is called as menstrual cycle. Å Many mammals exhibit such cycles only during favourable seasons in their reproductive phase and are called seasonal breeders. While those are reproductively active throughout their reproductive phase are called continuous breeders. n n n Sporangiospores (non-motile) – Rhizopus Å While in animals and other simple organisms, the term asexual is used unambiguously, in plants, the term vegetative reproduction is frequently used. Å In plants, units of vegetative propagation such as runner, rhizome, sucker, tuber, offset, bulb, etc., have capability to give rise to new offspring. These structures are known as vegetative propagules. Types of Vegetative Propagation in Plants and their Description Types of Vegetative Propagation in Plants Description 1. Natural Vegetative Propagation Root (Root tubers) Buds on the roots grow into leafy shoots above the ground and adventitious roots at the bases, e.g. sweet potato, guava, etc. Underground Modified stems possess buds which grow into new plants. Few types are Suckers, e.g. mint, Chrysanthemum Rhizomes, e.g. ginger, turmeric Bulbs, e.g. onion, garlic Tubers, e.g. potato Corms, e.g. Colocasia, Gladiolus. Creeping Few types include Runners, e.g. Oxalis, water hyacinth Offsets, e.g. Pistia. Aerial modified stems develop new plants when stem segments fall on the ground, e.g. cacti, Opuntia. Stem Adventitious buds develop on leaves, detach and form new plants, e.g. Bryophyllum. Leaves 2. Artificial Vegetative Propagation Å Cutting A small piece of any plant organ is used for propagation, e.g. leaves (Bryophyllum), roots (tamarind), stems (sugarcane), etc. Layering Roots are artificially induced on stem branches before these detach from the parent plant, e.g. jasmine, litchi, etc. Grafting Two plant parts, root system (stock) and shoot system (scion) from two different plants are joined to form a new plant, e.g. rose, apple, etc. Micropropagation Involves culturing of cells, tissues or organs to form callus which later differentiates to form a large number of plantlets. Water hyacinth (scourage of the water bodies or Terror of Bengal) propagates very quickly by vegetative mode and drains out dissolved O2 from water bodies. NEET Events in Sexual Reproduction The events of sexual reproduction may be grouped into three distinct stages namely, the pre-fertilisation, fertilisation and the post-fertilisation events. 1. Pre-fertilisation Events Å These are the events of sexual reproduction which take place before the fusion of gametes. These include gametogenesis and gamete transfer. Gametogenesis Å The process of formation of gametes is known as gametogenesis. Å The reproductive units in sexual reproduction are specialised cells called gametes. Å Depending upon the morphological similarity, gametes can be classified into homogametes or isogametes (in Cladophora) and heterogametes (in human). The gametes are generally of two kinds, i.e. male (antherozoid or sperm) and female (egg or ovum). KEY NOTES www.mediit.in 3 CHAPTER 01 > Reproduction in Organisms Å Sexuality in organisms On the basis of location of reproductive structure, sexuality in organisms can be classified as follows n n n n Å Å Homothallic and monoecious Both male and female reproductive structures are present on same individual (bisexual condition), e.g. in several fungi like Mucor and plants like maize, cucurbits and coconuts. Å When the female gamete undergoes development to form new organisms without fertilisation, the process is called as parthenogenesis, e.g. rotifers, honeybees, some lizards and birds (turkey). Å Depending upon, where does the syngamy occur, fertilisation may be of two types n Heterothallic and dioecious Male and female reproductive structures are present on separate individuals (unisexual condition), e.g. papaya and date palm. In flowering plants, the unisexual male flower is staminate, while female is pistillate. n Bisexual animals have both male and female reproductive organs in single individual, e.g. earthworm, sponge, leech, tapeworm, etc. These are also called as hermaphrodites. Unisexual animals have male and female reproductive organs in different individuals, e.g. cockroach, human, dog, etc. Cell division during gamete formation Gametes are always haploid, but they divide either by mitotic or meiotic division. The organisms belonging to Monera, Fungi, Algae and Bryophyta have haploid plant body. These organisms produce gametes by mitotic division. In pteridophytes, gymnosperms, angiosperms and most of the animals including humans, the parental body is diploid. In these organisms, specialised cells called meiocytes or gamete mother cells undergo meiosis that results in the formation of haploid gametes. It occurs in various ways in different organisms. n n n After the fusion of male and female gametes, following processes occur Zygote Å It is the beginning of new life. It is always diploid and ensures the continuity of race from generation to generation. Å Organism such as fungi, develops a thick wall around it that is resistant to external damaging factors. Å Zygote divides by meiosis to form haploid spores that grow into haploid individuals in case of organisms which lead haplontic life cycle, e.g. Volvox, Spirogyra, etc. Å In organisms with diplontic life cycle, zygote undergoes mitotic division and develops into an embryo, e.g. all flowering plants. In most organisms, male gamete is motile and female gamete is non-motile. Both gametes are motile in few fungi and algae. In algae, bryophytes and pteridophytes, gamete transfer takes place through water by producing many male gametes to ensure fertilisation because during gamete transfer, large number of male gametes are lost. In bryophytes and pteridophytes, male gametes are known as antherozoid. Embryogenesis Å Å It is the process of development of embryo from zygote. The events which occur in animals during embryogenesis are Mitosis (cell division or cleavage) occurs leading to the growth of embryo. n n n In self-fertilising or bisexual plants, e.g. peas, gamete transfer is easy as the anthers and stigma are closely located. In cross-fertilising plants, gamete transfer occurs by pollination. It is the process of transfer of pollen grains from anther to stigma, e.g. dioecious plants. 2. Fertilisation Å It is the complete and permanent fusion of two gametes from different parents or from the same parent to form a diploid zygote. This process is also called as syngamy. Internal fertilisation It is the fusion of gametes that take place inside the body, e.g. in fungi, higher animals such as birds, mammals and majority of plants. The number of ova produced is less, but a large number of male gametes are formed, as many of them fail to reach the ova. 3. Post-fertilisation Events Gamete Transfer Å External fertilisation It is the fusion of gametes that take place outside the body of an organism in external medium such as water, e.g. in bony fishes, frogs, etc. A large number of gametes are released in the surrounding medium by such animals. n Å Cells of embryo undergo differentiation and attain specific shape, size and function. Cell differentiation leads to the production of different tissues, organs and organ systems. Depending on the development of embryo the animals can be (i) Oviparous animals, e.g. reptiles and birds. Here, embryo develops outside the body of female (eggs). In these animals, the fertilised eggs are covered by hard calcareous shell. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 4 (ii) Viviparous animals, e.g. majority of mammals including humans. Here, embryo develops inside the body of female. Å (iii) Ovoviviparous animals, e.g. sharks and rattle snakes. Here, the female retains the eggs inside its body after fertilisation and allows the development of the embryo inside the body without providing extra nourishment to the developing embryo as the placenta is absent. The post-fertilisation events that occur in flowering plants are n n n n n Sepals, petals and stamens wither and shed off. Pistil remains attached to the plant. Zygote develops into embryo and the ovules develop into seed. Ovary develops into the fruit. Pericarp is produced as the wall of ovary. Seeds disperse by different agents and germinate into new plants after getting suitable conditions. Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Lifespan and Asexual Reproduction 5 Study the given figures and processes representing 1 Lifespan of tortoise is (a) (b) (c) (d) the binary fission in Amoeba. 100-150 years 250 years 20 years 1 year 2 Single-celled animals are said to be immortal because (a) (b) (c) (d) A they grow indefinitely in size they can tolerate any degree of change in temperature they can reproduce throughout their lifespan they continue to live as their daughter cells 3 Arrange the organisms shown below in the increasing order of their lifespans. Parrot (a) (b) (c) (d) Crocodile Parrot < Crow < Crocodile Crow < Crocodile < Parrot Crocodile < Parrot < Crow Parrot < Crocodile < Crow 4 Reproduction can be considered as (a) (b) (c) (d) a biological process a cycle of birth, growth and death a process that enables continuity of species All of the above Crow B D C E A. Daughter cells formation B. Enlargement of nucleus C. Parent cell D. Constricted cell formation E. Minimisation of pseudopodia Arrange the figures and processes in the correct sequence and select the correct answer. (a) (b) (c) (d) D→ C→ A→ B→ E C→ D→ A→ B→ E C→ E→ B→ D→ A D→ C→ B→ E→ A 6 Asexual reproduction is a method of reproduction in which participation of ……… takes place. (a) (b) (c) (d) one individual two individuals (same species) multi-individuals two individuals (different species) www.mediit.in CHAPTER 01 > Reproduction in Organisms 7 Clones are (a) (b) (c) (d) 5 17 Study the following diagram and the information morphologically similar individuals genetically similar individuals Both (a) and (b) None of the above given below. Conidia 8 ....... is the fastest method to obtain clones. (a) (b) (c) (d) Induced mutation Parasexual hybridisation Vegetative reproduction Parthenogenesis A B 9 Asexual reproduction is common in (a) (b) (c) (d) Mouth single-celled organisms plants with relatively simple organisation animals with relatively simple organisation All of the above Bud 10 Cell division is the mode of reproduction in (a) (b) (c) (d) monerans protists Both (a) and (b) None of the above 11 Reproduction in Amoeba is carried out through (a) gemmule formation (c) budding (b) binary fission (d) plasmotomy 12 In Amoeba, under unfavourable conditions, …A… takes place but under favourable conditions …B… occurs. Identify A and B. (a) (b) (c) (d) A Sporulation Encystation Binary fission Multiple fission B Encystation Sporulation Encystation Encystation 13 Zoospores are (a) (b) (c) (d) D C A. B. C. D. Zoospore of Chlamydomonas. Conidia of Penicillium. Buds in Hydra. Gemmules in sponge. All the above are (a) (b) (c) (d) bodies involved in sexual reproduction bodies involved in asexual reproduction bodies of young ones All the above are correct 18 Refer the given figures which show three different types of fission. A. B. motile gametes of Chlamydomonas non-motile gametes of sponges motile gametes of Hydra non-motile gametes of Penicillium C. 14 Asexual reproductive structures found in Penicillium are (a) conidia (c) gemmules (b) buds (d) zoospore 15 Gemmule formation is a common mode of reproduction in (a) Hydra (c) Penicillium (b) sponge (d) Amoeba 16 Hydra reproduces by (a) Budding (c) Gemmule formation (b) Fragmentation (d) Both (a) and (b) A. Longitudinal fission B. Transverse fission C. Multiple fission Select the option which correctly matches them with the organism in which they occur. A B C (a) (b) (c) (d) Euglena Plasmodium Euglena Euglena Plasmodium Paramecium Paramecium Paramecium Amoeba Euglena Escherichia Amoeba www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 6 19 Which one of the following pairs is not correctly match? CBSE-AIPMT 2015 Modes of reproduction Offset Rhizome Binary fission Conidia (a) (b) (c) (d) Examples (a) 2X (b) mitotic divisions (d) parthenogenesis Y X–Buds, Y–Nodes X–Nodes, Y–Adventitious buds X–Nodes, Y–Adventitious roots X–Eyes, Y–Nodes (d) X/2 (b) (c) (d) 27 The site of origin of the new plantlets in potato, Dahlia, ginger and banana is CBSE-AIPMT 2012 Onion – Bulb Ginger – Sucker Chlamydomonas – Conidia Yeast – Zoospores (c) X/4 below. I. The plant was introduced in India because of its beautiful flowers and shape of leaves. II. It can propagate vegetatively at a phenomenal rate and spread all over water body in a short period. III. It is very difficult to get rid of these plants. (a) 22 Which one of the following is correctly matched? (a) (b) (c) (d) (b) X 26 Identify the plant which contains the features given 21 Refer to the given figures and identify X and Y in these. (a) (b) (c) (d) (b) Antherozoid (d) Bulbil will be the number of chromosomes in a cell of its bulbil? NEET 2018 X (a) Offset (c) Rhizome 25 If a leaf cell of Agave have X chromosome, then what Water hyacinth Banana Sargassum Penicillium 20 Offsets are produced by (a) parthenocarpy (c) meiotic divisions 24 Which of the following is not a vegetative propagule? (a) (b) (c) (d) floral buds present on stem internodes of modified stem nodes of modified stem adventitious buds present on root 28 Which one of the following options shows two plants 23 Choose the option with correct identification of A, B, C, D and E given below. Germinating Eyes eye buds Buds in which new plantlets arise from the same organ? (a) (b) (c) (d) Guava and ginger Potato and sweet potato Dahlia and mint Potato and sugarcane 29 Some organisms are capable of asexual or sexual Adventitious roots B A Leaves Adventitious roots C D E A B (a) Tuber Rhizome Eyes C Leaf bud Offset (b) Offset Eyes Leaf bud Stolon Sucker (c) Offset Leaf buds Eyes Stolon Sucker (d) Tuber Rhizome Leaf buds Offset Bulbil D E reproduction. Under favourable conditions, reproduction proceeds asexually. When conditions become more stressful reproduction switches to a sexual mode. Why? (a) Sexual reproduction is simple and more rapid allowing larger numbers of offspring to be produced (b) Sexual reproduction requires two separate individuals, who can mutually provide nutrient support during stress (c) Sexual reproduction produces individuals with new combinations of recombined chromosomes increasing diversity (d) Asexual reproduction requires more energy 30 A scion is grafted to a stock. The quality of fruits produced will be determined by the genotype of AIIMS 2018 (a) stock (c) Both (a) and (b) (b) scion (d) Neither (a) nor (b) www.mediit.in CHAPTER 01 > Reproduction in Organisms 7 TOPIC 2 ~ Sexual Reproduction 31 Which one of the following generates new genetic combinations leading to variation? (a) (b) (c) (d) Vegetative reproduction Parthenogenesis Sexual reproduction Nucellar polyembryony 32 Sexual reproduction involves formation of male and female gametes by (a) (b) (c) (d) same individual different individual of opposite sex Both (a) and (b) All of the above 33 The growth phase of an organism before attaining sexual maturity is referred to as (a) juvenile phase (c) Both (a) and (b) (b) pre-reproductive phase (d) None of these 34 Select the correct sequence from the following. I. Juvenile phase→ Senescent phase→ Reproductive phase II. Juvenile phase→ Reproductive phase→ Senescent phase III. Reproductive phase→ Juvenile phase→ Senescent phase IV. Pre-reproductive phase→ Reproductive phase→ Senescent phase (a) I and II (c) III and IV (b) I and IV (d) II and IV 35 Which one of the following flowers only once in its lifetime? (a) Mango (c) Bamboo species 39 Select the correct sequence of events. NEET (Odisha) 2019 NEET 2016, 13 NEET 2018 (a) Gametogenesis → Gamete transfer → Syngamy → Zygote → Cell division (Cleavage) → Cell differentiation → Organogenesis (b) Gametogenesis → Gamete transfer → Syngamy → Zygote → Cell divison (Cleavage) → Organogenesis→ Cell differentiation (c) Gametogenesis → Syngamy → Gamete transfer → Zygote → Cell division (Cleavage) → Cell differentiation → Organogenesis (d) Gametogenesis → Gamete transfer → Syngamy → Zygote → Cell differentiation → Cell division (Cleavage) → Organogenesis 40 Identify the events (A, B, D and E) of sexual reproduction given below. n Pre-fertilisation event A E B CD Post-fertilisation event Fertilisation 2n Choose the correct option. (a) A–Gamete transfer, B–Gametogeneis, D–Zygote formation, E–Embryogenesis (b) A–Gametogeneis, B–Gamete transfer, D–Zygote formation, E–Embryogenesis (c) A–Gametogeneis, B–Zygote formation, D–Gamete transfer, E–Embryogenesis (d) A–Gametogeneis, B–Gamete transfer, D–Embryogenesis, E–Zygote formation 41 Identify the type of gametes shown in figure A, B and C, respectively. (b) Jackfruit (d) Papaya Macrogamete (female) Flagella 36 Strobilanthes kunthiana is also called (a) Neelakurinji (c) Hara kuranji (b) Peela kuranji (d) Kala kuranji Microgamete (male) A 37 Oestrus cycle is cyclic change in the activities of ovaries and accessory duct in non-primates during B Female gamete (ovum) (a) reproductive (seasonal) period (b) maturation period (c) ageing period (d) juvenile period Male gametes (sperms) 38 Organisms reproducing throughout the year are called …… breeders, e.g. … and those who show recurring sexual activity are called …… breeders, e.g. … . (a) (b) (c) (d) continuous, sparrow, seasonal, hen seasonal, lizard, continuous, hen continuous, man, seasonal, tiger seasonal, hen, continuous, tiger C (a) (b) (c) (d) A–Heterogametes, B–Isogametes, C–Homogametes A–Homogametes, B–Isogametes, C–Heterogametes A–Isogametes, B–Heterogametes, C–Heterogametes A–Heterogametes, B–Heterogametes, C–Isogametes www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 8 42 Name the type of gametes found in algae. (a) Homogametes (c) Anisogametes (b) Heterogametes (d) All of these 43 What is male gamete called in heterogametic 51 If the parent body is haploid then the gametes are (a) haploid (c) triploid (b) diploid (d) None of these 52 In diploid organism the gamete producing cells are called condition? (a) Antherozoid (c) Egg (b) Sperm (d) Both (a) and (b) 44 The condition, in which, both male and female reproductive organs are found on the same plant, is called (a) unisexual (c) monoecious (a) gamete mother cell (c) Both (a) and (b) 53 Which of the following is an incorrect combination of organism with its correct chromosome number in meiocyte and in gamete? (b) bisexual (d) Both (b) and (c) 45 Figure P represents the reproductive organs of a plant, Chara and figure Q represents the reproductive organs of an animal, earthworm. Select the option which correctly identifies male reproductive organs of the two organisms. (b) meiocytes (d) None of these Name of organisms Chromosomes Chromosomes number in meiocyte number in gamete (a) Butterfly 380 190 (b) Potato 16 08 (c) Maize 20 10 (d) Apple 34 17 54 Identify the sequence of events shown in the diagram below. C A D B P Q (a) A and D (b) B and C (c) A and C (d) B and D 46 The condition in which male and female parts are present on different organisms, is called (a) heterothallic (c) unisexual (b) dioecious (d) All of these 47 In flowering plants, the unisexual male flower is called …A… while the female is called …B… . Flowering plants may be monoecious, e.g. …C… or dioecious, e.g. …D… . Complete the paragraph by filling up the blanks. (a) (b) (c) (d) A–staminate, B–pistillate, C–date palm, D–coconut A–pistillate, B–staminate, C–date palm, D–papaya A–pistillate, B–staminate, C–Cucurbita, D–coconut A–staminate, B–pistillate, C–Cucurbita, D–papaya 48 Name the type of gametes formed in staminate and pistillate flower, respectively. (a) Stamen, pollen (c) Stamen, ovum (b) Antherozoid, egg (d) Ovum, antherozoid 49 Which of the following is hermaphrodite? (a) Ant (b) Aphids (c) Earthworm (d) Cockroach 50 Which among the following is unisexual species? (a) Tapeworm (c) Cockroach (b) Leech (d) All of these (a) Fission of gametes → New individual → Zygote (b) Fusion of gametes → Zygote → New individual (cell 2n) (c) Fission of gametes → Zygote → New individual (cell 2n) (d) Stages in the gametogenesis 55 Self-fertilisation occurs in the (a) bisexual flower (c) Both (a) and (b) (b) unisexual flower (d) dioecious flower 56 In which of the following organisms self-fertilisation is seen? (a) Peas (c) Sweet potato (b) Mustard (d) All of these 57 Which of the following options is/are correct about pollination? (a) (b) (c) (d) Occurs in almost all flowering plants Facilitates pollen transfer to stigma Both (a) and (b) None of the above 58 Essential and most critical event in sexual reproduction is (a) (b) (c) (d) fertilisation division in male and female gametes Both (a) and (b) None of the above www.mediit.in CHAPTER 01 > Reproduction in Organisms 66 Embryogenesis involves 59 Fusion of male and female gametes is called (a) syngamy (c) Both (a) and (b) (b) fertilisation (d) heterogamy 60 In some plants, the female gamete develops into embryo without fertilisation. This phenomenon is known as (a) parthenocarpy (c) parthenogenesis NEET 2019 (b) syngamy (d) autogamy 61 Syngamy may occur in ………… . (a) external medium (c) Both (a) and (b) (b) internal medium (d) None of these 62 ‘Organisms exhibiting external fertilisation release a large number of gametes’. Why? (a) These organisms shows great synchrony between the sexes (b) In order to enhance the chances of syngamy (c) To produce large number of offsprings as they are vulnerable to predators (d) All of the above 63 Internal fertilisation is the one in which syngamy (a) (b) (c) (d) 9 occur outside the body occur inside the body is followed by meiosis None of the above (a) (b) (c) (d) formation of embryo from zygote cell division via meiosis and differentiation Both (a) and (b) None of the above 67 Choose the incorrect pair. (a) Cell division in embryo – Increase the number of cells (b) Cell differentiation – Form specialised tissues and organs (c) Eggs covered by hard calcareous shell – Oviparous animals (d) Zygote develops outside the body –Viviparous animals 68 Chances of survival of young ones are more in the case of............. individuals. (a) oviparous (c) ovoviviparous (b) viviparous (d) None of these 69 Offsprings of oviparous animals have less chances of survival as compared to those of viviparous animals because (a) (b) (c) (d) proper embryonic care and protection is absent embryo does not develop completely progenies are of smaller size genetic variations do not occur 70 What does ‘P’ signifies in the diagram given below? 64 Diploid zygote is universal in (a) (b) (c) (d) All sexually reproducing organisms All asexually reproducing organisms All sexually and asexually reproducing organisms Only plants and animals S S P P 65 Life begins in all sexually reproducing organism from a (a) single-celled zygote (c) thick-walled zygote (b) double-celled zygote (d) All of these (a) Pistil (c) Thin pericarp (b) Thick pericarp (d) Pollen tube NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Direction (Q. No. 71-80) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 71 Assertion (A) A plant can be retained and multiplied indefinitely without any change or variation through asexual reproduction. Reason (R) Asexual reproduction does not involve meiosis and syngamy. 72 Assertion (A) Offspring formed by asexual reproduction are called clones. Reason (R) Clones are morphologically similar. 73 Assertion (A) Reproduction by zoospores occur in some higher fungi. Reason (R) Zoospores are motile and flagellated spores. 74 Assertion (A) Zygote is the link between two generations. Reason (R) Zygote is the product of two gametes and the producer of the next generation. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 10 75 Assertion (A) Vegetative reproduction is a kind of asexual reproduction in plants. Reason (R) Vegetative propagules give rise to offspring. 76 Assertion (A) In perennial plant species, it is difficult to define vegetative, reproductive and senescent phases. Reason (R) Perennial plants have very short lifespan. 77 Assertion (A) Gametes formed in sexual reproduction are haploid in nature. Reason (R) Meiocytes undergo meiosis to form gametes. 78 Assertion (A) Papaya is a dioecious plant. Reason (R) Dioecious plants are those that have their reproductive structures on same plants. 79 Assertion (A) In external fertilisation, syngamy occurs inside the female. Reason (R) The offspring produced by external fertilisation are vulnerable to predators. 80 Assertion (A) In flowering plants, zygote is formed inside the ovule. Reason (R) The ovule develop into seed after fertilisation. II. Statement Based Questions 81 Which one of the following statement regarding post-fertilisation development in flowering plants is NEET 2019 incorrect? (a) Zygote develops into embryo (b) Central cell develops into endosperm (c) Ovules develop into embryo sac (d) Ovary develops into fruit 82 Choose the incorrect statement about gemmules. (a) They resist dessication JIPMER 2019 (b) They are internal buds (c) They are asexual structure which are produce by binary fission (d) They can give rise to new organisms 83 Which of the following statements is correct? (a) All the individuals of a species have exactly the same lifespan (b) Smaller organisms always have shorter lifespan and vice-versa (c) Lifespan of an organism is the time period from its birth to its natural death (d) No organism may have a lifespan of several hundred years 84 Which one of the following statements is incorrect? NEET 2016 (a) Offspring produced by the asexual reproduction are called clone (b) Microscopic motile asexual reproductive structures are called zoospores (c) In potato, banana and ginger, the plantlets arise from the internodes present in the modified stem (d) Water hyacinth, growing in the standing water, drains oxygen from water that leads to the death of fishes 85 Mark the incorrect statement. (a) Perennial species shows clear cut vegetative, reproductive and senescent phases (b) End of vegetative phase mark the beginning of reproductive phase (c) Bamboo species flower only once in their lifetime (d) The reproductive phase is of variable duration in different organisms 86 Choose the incorrect statement for events in sexual reproduction. (a) All sexually reproducing organisms exhibits events and processess having fundamental similarity (b) Structures associated with sexual reproduction vary among different groups of organisms (c) Pre-fertilisation, fertilisation and post-fertilisation is the exact sequence of events occurring in sexual reproduction (d) None of the above 87 Which one of the following statements is incorrect? (a) Gamete receive only one set of chromosomes (b) Meiosis is a reductional division occurring in both haploid and diploid organisms (c) Male gametes are always produced in less quantity than female gametes (d) In seed plants, pollen grains are the carriers of male gametes 88 Go through the following statements. I. Cell division is a mode of reproduction in algae and fungi. II. Amoeba and Paramecium divide by fragmentation. III. In yeast, cell division is unequal and small buds are produced. IV. Zoospores are macroscopic non-motile structures. Choose the incorrect statements. (a) I and III (c) I, II and IV (b) III and IV (d) Only III 89 Read the following statements about asexual reproduction and select the correct ones. I. It involves a single parent. II. It is slower than sexual reproduction. III. It produces progeny that are genetically identical with the parent, but not with one another. www.mediit.in CHAPTER 01 > Reproduction in Organisms IV. The progeny of asexual reproduction can be termed as clones. (a) I and II (c) I and IV (b) II and III (d) I, III and IV 90 Read the following statements and select the correct ones. I. Conidia are the asexual propagules restricted to kingdom–Fungi. II. A piece of potato tuber having at least one eye (or node) is capable of giving rise to a new plant. III. Ginger propagates vegetatively with the help of its underground roots. IV. Fleshy buds which take part in vegetative propagation are called bulbils, present in Dioscorea, Agave, etc. (a) II and III (c) I, II and IV (b) I and IV (d) I, II and III 91 Find out the incorrect statement. I. Lifespans of organisms are necessarily correlated with their sizes. II. The sizes of crows and parrots are not very different, but still their lifespans vary extremely. III. A peepal tree has much shorter lifespan as compared to a mango tree. IV. Reproduction is essential for continuity of species on the earth. (a) I and III (c) Only IV (b) I, II and III (d) II and III 92 Consider the following statements. I. Many plants propagate vegetatively even though they bear seeds. II. Sweet potatoes multiply vegetatively by root tubers. Select the correct option. (a) (b) (c) (d) I is true, but II is false Both I and II are false I is false, but II is true Both I and II are true 93 Read the following statements. I. Organisms exhibiting external fertilisation show great synchrony between the sexes and release a large number of gametes. II. A major disadvantage of external fertilisation is that the offspring are extremely vulnerable to predators. III. In gymnosperms, male gametes reach egg with the help of water as a medium. IV. Zygote is a vital link that ensures continuity of species between organisms of one generation and the next. V. Every sexually reproducing organisms begin their life as a single-celled zygote. Which of the above statements are correct? (a) I, II and III (c) I, II, IV and V (b) I, II, III and V (d) I, II, III and IV 11 94 Read the following statements. I. Eichhornia contributes extra oxygen to the water bodies which reduces the mortality of fishes. II. Zingiber propagates vegetatively by tap roots. III. Fleshy buds which take part in vegetative propagation are called bulbils, e.g. Agave. IV. A potato tuber having atleast one eye, i.e. axillary bud can form a new plant. V. Bryophyllum posssesss leaf buds. Which of the above statements is/are correct? (a) (b) (c) (d) I, II and III III, IV and V I, II and V I, II, III, IV and V 95 Read the following statements. I. The vegetative phase is of same duration in different organisms. II. Clear-cut vegetative, reproductive and senescent phases can be observed in monocarpic plants. III. Bambusa differs from Strobilanthes kunthiana (Neelakurinji) in the length of juvenile phase and being monocarpic. IV. The end of juvenile/vegetative phase in angiosperms is seen when they come to flower. V. Sexual mode of reproduction is present in most animals. Which of the above statement is/are incorrect? (a) II, IV and V (c) III, IV and V (b) II and III (d) I and III 96 Read the following statements. I. Interaction between hormones and certain environmental factors regulate the reproductive processes and the associated behavioural expression of organisms. II. In animals, but not in plants, hormones are responsible for the transitions between juvenile, reproductive and senescent phases. III. After attainment of maturity, all sexually reproducing organisms exhibit events and processes that have remarkable fundamental similarity, though the structure associated with sexual reproduction are indeed very different. IV. The post-fertilisation events include gametogenesis and gamete transfer. V. In majority of the sexually reproducing organisms, the gametes produced are morphologically distinct types, i.e. heterogametes. Which of the above statements are correct? (a) (b) (c) (d) I, III and V I, II and IV III, IV and V II, III and V www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 12 III. Matching Type Questions Codes A (a) 1 (b) 4 (c) 4 (d) 2 97 Match the following columns. A. B. C. D. E. Column I (Asexual reproduction types) Binary fission Zoospore Conidium Budding Gemmules Codes A (a) 1 (b) 2 (c) 1 (d) 1 B 4 1 2 4 C 5 4 3 3 D 3 3 4 2 Column II (Examples) 1. 2. 3. 4. 5. Algae Amoeba Hydra Penicillium Sponge B. Dioecious 2. Fucus C. Isogametes 3. Coconut D. Heterogametes 4. Papaya Codes A (a) 4 (c) 3 B 3 4 C 1 1 D 2 2 A (b) 1 (d) 3 C 2 2 D 4 1 Column II A. External fertilisation 1. Human beings B. Internal fertilisation 2. Algae and fishes C. Ovipary 3. Bryophytes, pteridophytes and birds Codes A (a) 4 (c) 2 B 1 3 4 C 2 4 D 3 1 2n = 12 B. Fruit fly 2. 2n = 16 C. Onion 3. 2n = 46 D. House fly 4. 2n = 08 A (b) 3 (d) 4 B 2 4 1 4 C 4 3 4 2 D 3 2 3 1 B 1 2 C 4 1 Column II (Reproduce by) A. Ginger 1. Tuber B. Yeast 2. Offset C. Potato 3. Rhizome D. Water hyacinth 4. Budding Codes A (a) 4 (c) 3 B 1 4 C 2 1 D 3 2 Column I (Floral parts) D 2 3 Column II A. Oestrus cycle 1. Spirogyra B. Conjugation 2. Rose C. Stem cuttings 3. Monkey, apes, humans D. Menstrual cycle 4. Cows, sheeps, rats A (b) 3 (d) 4 B 1 2 C 4 1 D 2 3 103 Match the following columns. Reptiles and birds 100 Match the following columns. Column I 1. Column I (Organisms) B 3 4 Column I Vivipary Human 102 Match the following columns. 99 Match the following columns. D. Column II (Number of chromosomes) A. Codes A (a) 1 (b) 1 (c) 2 (d) 3 Column II (Examples) 1. Cladophora D 4 3 2 3 Column I (Organisms) 98 Match the following columns. A. Monoecious C 2 2 3 4 101 Match the following columns. E 2 5 5 5 Column I (Terms) B 3 1 1 1 Column II (Converted to) A. Ovary 1. Pericarp B. Ovule 2. Perisperm C. Ovary wall 3. Fruit D. Nucellus 4. Seed Codes A (a) 3 (b) 3 (c) 1 (d) 1 B 4 2 2 3 C 1 1 3 2 D 2 4 4 4 www.mediit.in CHAPTER 01 > Reproduction in Organisms 13 NCERT Exemplar MULTIPLE CHOICE QUESTIONS 104 A few statements with regard to sexual reproduction are given below. I. Sexual reproduction does not always require two individuals. II. Sexual reproduction generally involves gametic fusion. III. Meiosis never occurs during sexual reproduction. IV. External fertilisation is a rule during sexual reproduction. Choose the correct statements from the options given below. (a) I and IV (b) I and II (c) II and III (d) II and IV 105 The term ‘clone’ cannot be applied to offspring formed by sexual reproduction because (a) offspring do not possess exact copies of parental DNA (b) DNA of only one parent is copied and passed on to the offspring (c) offspring are formed at different times (d) DNA of parent and offspring are completely different 106 The male gametes of rice plant have 12 chromosomes in their nucleus. The chromosome number in the female gamete, zygote and the cells of the seedling will be, respectively (a) 12, 24, 12 (c) 12, 24, 24 (b) 24, 12, 12 (d) 24, 12, 24 107 Amoeba and yeast reproduce asexually by fission and budding, respectively because they are (a) microscopic organisms (b) heterotrophic organisms (c) unicellular organisms (d) uninucleate organisms 108 Appearance of vegetative propagules from the nodes of plants such as sugarcane and ginger is mainly because (a) (b) (c) (d) nodes are shorter than internodes nodes have meristematic cells nodes are located near the soil nodes have non-photosynthetic cells 109 Choose the correct statement from amongst the following. (a) (b) (c) (d) Dioecious organisms are seen only in animals Dioecious organisms are seen only in plants Dioecious organisms are seen in both plants and animals Dioecious organisms are seen only in vertebrates 110 There are various types of reproduction. The type of reproduction adopted by an organism depends on (a) (b) (c) (d) the habitat and morphology of the organism morphology of the organism morphology and physiology of the organism the organism’s habitat, physiology and genetic makeup 111 Which of the following is a post-fertilisation event in flowering plants? (a) Transfer of pollen grains (b) Embryo development (d) Formation of pollen grains (c) Formation of flower 112 A few statements describing certain features of reproduction are given below. I. Gametic fusion takes place. II. Transfer of genetic material takes place. III. Reduction division takes place. IV. Progeny have some resemblance with parents. Select the options that are true for both asexual and sexual reproduction from the options given below. (a) I and II (b) II and III (c) II and IV (d) I and III 113 Asexual method of reproduction by binary fission is common to which of the following? I. Some eukaryotes II. All eukaryotes III. Some prokaryotes IV. All prokaryotes (a) I and II (b) II and III (c) I and III (d) III and IV 114 A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic division occurs after the formation of zygote. The adult filament of this alga has (a) (b) (c) (d) haploid vegetative cells and diploid gametangia diploid vegetative cells and diploid gametangia diploid vegetative cells and haploid gametangia haploid vegetative cells and haploid gametangia 115 Given below are a few statements related to external fertilisation. Choose the correct statements. I. The male and female gametes are formed and released simultaneously. II. Only a few gametes are released into the medium. III. Water is the medium in a majority of organisms exhibiting external fertilisation. IV. Offspring formed as a result of external fertilisation have better chance of survival than those formed inside an organism. (a) III and IV (b) I and III (c) II and IV (d) I and IV 116 The statements given below describe certain features that are observed in the pistil of flowers. I. Pistil may have many carpels. II. Each carpel may have more than one ovule. III. Each carpel has only one ovule. IV. Pistil have only one carpel. Choose the statements that are true from the options given below. (a) I and II (b) I and III (c) II and IV (d) III and IV www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 14 117 Which of the following situations correctly describe the similarity between an angiosperm egg and a human egg? I. Eggs of both are formed once in a lifetime. II. Both the angiosperm egg and human egg are stationary. III. Both the angiosperm egg and human egg are motile transported. IV. Syngamy in both results in the formation of zygote. Choose the correct answer from the options given below. (a) (b) (c) (d) 119 Offspring formed by sexual reproduction exhibit more variation than those formed by asexual reproduction because (a) sexual reproduction is a lengthy process (b) gametes of parents have qualitatively different genetic composition (c) genetic material comes from parents of two different species (d) greater amount of DNA is involved in sexual reproduction 120 There is no natural death in single-celled organisms like Amoeba and bacteria because II and IV Only IV III and IV I and IV (a) (b) (c) (d) 118 Which of the following statements, support the view that elaborate sexual reproductive process appeared much later in the organic evolution? I. Lower groups of organisms have simpler body design. II. Asexual reproduction is common in lower groups. III. Asexual reproduction is common in higher groups of organisms. IV. The high incidence of sexual reproduction in angiosperms and vertebrates. Choose the correct answer from the options given below. (a) I, II and III (c) I, II and IV they cannot reproduce sexually they reproduce by binary fission parental body is distributed among the offspring they are microscopic 121 Identify the incorrect statement. (a) In asexual reproduction, the offspring produced are morphologically and genetically identical to the parent (b) Zoospores are sexual reproductive structures (c) In asexual reproduction, a single parent produces offspring with or without the formation of gametes (d) Conidia are asexual structures in Penicillium 122 The number of chromosomes in the shoot tip cells of a maize plant is 20. The number of chromosomes in the microspore mother cells of the same plant will be (a) 20 (c) 40 (b) I, III and IV (d) II, III and IV (b) 10 (d) 15 Answers Mastering NCERT with MCQs 1 11 21 31 41 51 61 (a) (b) (b) (c) (c) (a) (c) 2 12 22 32 42 52 62 (d) (b) (a) (c) (d) (c) (d) 3 13 23 33 43 53 63 (b) (a) (d) (c) (d) (b) (b) 4 14 24 34 44 54 64 (d) (a) (b) (d) (d) (b) (a) 5 15 25 35 45 55 65 (c) (b) (b) (c) (b) (a) (a) 6 16 26 36 46 56 66 (a) (d) (b) (a) (d) (d) (a) 7 17 27 37 47 57 67 (c) (b) (c) (a) (d) (c) (d) 8 18 28 38 48 58 68 (c) (d) (d) (c) (b) (c) (b) 9 19 29 39 49 59 69 (d) (c) (c) (a) (c) (c) (a) 10 20 30 40 50 60 70 (c) (b) (b) (b) (c) (c) (b) NEET Special Types Questions 71 81 91 101 (a) (c) (a) (d) 72 82 92 102 (b) (c) (d) (c) 73 83 93 103 (d) (c) (c) (a) 74 (a) 84 (c) 94 (b) 75 (b) 85 (a) 95 (d) 76 (c) 86 (d) 96 (a) 77 (a) 87 (c) 97 (b) 78 (c) 88 (c) 98 (c) 79 (d) 89 (c) 99 (c) 80 (a) 90 (c) 100 (b) 107 (c) 117 (b) 108 (b) 118 (c) 109 (c) 119 (b) 110 (d) 120 (c) 111 (b) 121 (b) 112 (c) 122 (a) 113 (c) NCERT Exemplar Questions 104 (b) 114 (d) 105 (a) 115 (b) 106 (c) 116 (a) www.mediit.in 15 CHAPTER 01 > Reproduction in Organisms Answers & Explanations organisms (e.g. Amoeba). It is due to the fact that they divide and continue to live as their daughter cells. 3 (b) The organisms with the increasing order of their lifespans are crow (15 years) < crocodile (60 years) < parrot (140 years). 7 (c) Offspring produced by asexual (vegetative) reproduction are called as clones. They are morphologically and genetically similar individuals. 26 (b) The figure in option (b) represents water hyacinth. 28 29 10 (c) Cell division is the common mode of reproduction in Monera and Protista as these contain single-celled organisms. In this process, the cell divides by mitosis into two parts and each part continues to live on as a daughter cell. 13 (a) Zoospores are motile gametes. These are commonly found in the fungi and plant kingdom, e.g. Chlamydomonas. 30 14 (a) Conidia are the asexual reproductive structures found in Penicillium. They are non-motile gametes which develops singly or in chain on the parent body. 15 (b) Gemmule formation is a common mode of asexual reproduction in sponges. In this, the buds are formed within the parent body and later get released into the environment to form a new organism. 31 19 (c) Option (c) contains the incorrectly matched pair. It can be corrected as Binary fission is observed in Amoeba and Sargassum reproduces through fragmentation. Rest of the pairs are correctly matched. 20 (b) Offsets are produced by mitotic divisions. These are one internode long runners that occur in some aquatic plants. Breaking of offsets helps in vegetative propagation. These give rise to new plants, e.g. Eichhornia. 22 (a) Option (a) contains the correctly matched pair. Rest of the matches are incorrect and can be corrected as l l l Ginger propagates by rhizome formation. Chlamydomonas reproduces by zoospores. Yeast reproduces by budding. 32 (c) Sexual reproduction involves formation of the male 33 34 35 24 (b) Antherozoid is not a vegetative propagule. In majority of the sexually reproducing organisms, the motile male gamete is called as antherozoid or sperm whereas the other options represent vegetative propagules which have the capability of giving rise to new offspring. 25 (b) In Agave, bulbils are modified floral buds that develop on the flowering axis, so chromosome number in a cell of bulbil will be equal to that of the leaf cell of Agave, i.e. n = X. This plant was introduced in India because of its beautiful flowers and the shape of its leaves. This plant can propagate at a very fast rate, spreading all over the water body in a short amount of time. However, this plant becomes invasive and is very difficult to get rid of. (d) In both potato and sugarcane, new plantlets arise from the nodes present in their modified stems. (c) Sexual reproduction produces individuals with new combinations of recombined chromosomes. This produces variations among offspring. When conditions become more stressful, an organism switches to sexual mode of reproduction so as to produce offspring with variations. These enable the offspring to adapt to the stressful conditions and successfully survive and reproduce. (b) In grafting technique, parts of two plants are joined to form a composite plant. One part represents the strong root system called stock and the other part having better flower or fruit yield on shoot is called the scion. Hence, the fruit produced in such plants would have the genotype of the scion. (c) Sexual reproduction brings about variation through genetic recombinations due to the participation of two parents. In this, the random union of gametes contributes in forming new combinations of characters. 37 43 and female gametes, either by the same individual or by different individuals of the opposite sex. (c) The growth phase of an organism before attaining sexual maturity is referred to as juvenile phase and pre-reproductive phase. In plants it is known as vegetative phase. (d) Before reproducing sexually, organisms reach a stage of growth and maturity in their life which is known as juvenile phase or pre-reproductive phase. The end of this phase, marks the beginning of the reproductive phase and this phase finally leads to old age or senescent phase. (c) Bamboo plants are perennial, monocarpic plants. They flower only once in their lifetime, usually after 50-100 years producing a large number of fruits and then these plants die. (a) Generally, oestrus cycle takes place in the seasonal breeders, e.g. non-primates. It is the cyclic change in the activity of ovaries and accessory duct during the reproductive (seasonal) period. (d) Male gametes are called antherozoids in case of lower organisms like fungi and algae, and in higher organisms like mammals, reptiles, etc., these are called sperms. Answers & Explanations 2 (d) No individual is immortal except some single-celled www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 16 44 (d) Hermaphrodite/bisexual/monoecious/homothallic 45 46 51 52 53 54 59 Answers & Explanations 60 63 64 are terms used when both the male and female reproductive organs are present in same organism. Hermaphrodite is used for animals. Bisexual and monoecious are used for both animal and plant. Homothallic is used for fungi. (b) In figure P, B–represents the antheridium (male sex organ) of Chara. In figure Q, C–represents the testis sac with testis of earthworm. (d) Heterothallic/dioecious/unisexual are terms used when the sexes, i.e. male and female reproductive parts are present on different organisms. Heterothallic is used for fungi. Unisexual and dioecious used for both animals and plants. (a) Irrespective of the fact, whether the organism is haploid or diploid, it has haploid gametes. In haploid parents, mitosis produces haploid gametes. In diploid parents, meiosis produces haploid gametes. (c) Gamete mother cells are called gamete producing cells. In these, meiotic cell division takes place for the production of haploid gametes. These are also called meiocytes (diploid). (b) Option (b) represents the incorrect combination. It can be corrected as 16 and 8 are the chromosome numbers in meiocyte and gametes, respectively in Allium cepa (onion). Potato has 48 and 24 chromosomes in meiocyte and in gametes, respectively. Rest all options are correct combinations. (b) In the given diagram, three figures are shown. First figure indicates the fusion of male and female gametes. Second figure indicates the formed zygote because there are two nuclei visible in completely fused condition. Third figure indicates a complete new cell after fusion is completed. Now, it can be called as a new individual. (c) Syngamy or Fertilisation refers to the phenomenon of the haploid fusion of male and female gametes that leads to the formation of a diploid cell. (c) Parthenogenesis is the process by which the female gamete develops into embryo without fertilisation. It is of two types, i.e. haploid and diploid. In the former, embryo develops from haploid egg and in the later a diploid egg develops into embryo. (b) In internal fertilisation, fusion of gametes (syngamy) takes place inside the female reproductive tract. This process provides direct protection from the environment to the developing progeny. (a) The presence of diploid zygote is universal in all sexually reproducing organisms irrespective of the fact that, the parents are haploid or diploid. In haploid parent condition, the diploid zygote undergoes meiosis and becomes haploid body again, while in diploid organisms, the diploid zygote changes to diploid individual after undergoing mitosis. 65 (a) During fertilisation two haploid cells, a female and a 67 68 71 72 73 74 75 76 77 male gamete combine to form a single diploid cell (2n) called zygote, from where every sexually reproducing organism begin its life. (d) Option (d) contains the incorrect match. It can be corrected as In viviparous animals, zygote develops inside the body of female. Rest of the pairs are correct. (b) In viviparous animals, the zygote develops into a young one inside the body of female organism. Thus, the chances of survival of young ones are greater in these animals because these young ones are provided with proper embryo care and protection. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. In asexual mode of reproduction, there is no variation and the genetic constituent of offspring remains the same. Because in this process, offspring is produced without the involvement of gametic fusion (syngamy) and involves only mitotic cell division. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Asexual reproduction involves the participation of a single parent to produce an offspring. As a result, the offspring produced are morphologically and genetically similar to one another and also to their parents and can be referred to as clone. (d) Assertion is false, but Reason is true. Assertion can be corrected as Reproduction by zoospores occurs in some lower fungi, e.g. Albugo. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Zygote is the product of fusion of two gametes. It is a vital link that ensures the continuity of species between the organisms of one generation and the next. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Vegetative reproduction is a kind of asexual reproduction in plants in which offspring are formed by vegetative propagules like tuber, sucker, runner, etc., rather than by fusion of gametes. (c) Assertion is true, but Reason is false and it can be corrected as Perennial plants have a long lifespan. Hence, it becomes very difficult to define and study their vegetative, reproductive and senescent phases. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Meiocytes (gamete mother cell) are specialised cells in diploid organisms that undergo meiosis to form haploid gametes. Gametes have only one set of chromosome as that of meiocytes. www.mediit.in 17 CHAPTER 01 > Reproduction in Organisms 79 80 81 82 83 corrected as Dioecious is the term used to describe unisexual condition. Dioecious plants have their reproductive structures on different plants, e.g. papaya and Marchantia. (d) Assertion is false, but Reason is true. Assertion can be corrected as In external fertilisation, fertilisation or syngamy occurs outside the female body. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. In flowering plants, the zygote is formed inside the ovule and after fertilisation, the zygote develops into embryo and the ovules into seeds. (c) The statement in option (c) is incorrect and it can be corrected as During post-fertilisation event, ovule develops into seed not embryo sac. Rest of the statements regarding post-fertilisation development in flowering plants are correct. (c) Statement in option (c) is incorrect. It can be corrected as Gemmules are asexual structures, produced by organisms (e.g. sponge) during unfavourable condition by the process of internal budding. Rest of the statements are correct about gemmules. (c) Statement in option (c) is correct. Rest of the statements are incorrect and can be corrected as l l l All the individuals of a species have different lifespan. Smaller organisms do not always have a shorter lifespan and vice-versa. Some organisms may have a lifespan of several hundred years. 84 (c) Statement in option (c) is incorrect. It can be corrected as In potato, banana and ginger, new plantlets always arise from the nodes of the modified stem. Rest of the statements are correct. 85 (a) Statement in option (a) is incorrect. It can be corrected as Perennial species do not show clear cut vegetative, reproductive and senescent phases. Rest of the statements are correct. 87 (c) Statement in option (c) is incorrect. It can be corrected as The number of male gametes produced is several thousand times more than the number of female gametes produced. Rest of the statements are correct. 88 (c) Statements I, II and IV are incorrect and can be corrected as. l Cell division is a mode of reproduction in monerans and protists. l l Amoeba and Paramecium mostly divide by binary fission. The zoospores are microscopic and motile asexual reproductive bodies. Remaining statement III is correct. 89 (c) Statements I and IV are correct. But statements II and III are incorrect and can be corrected as l l Asexual reproduction is faster than sexual reproduction. Asexual reproduction produces progeny that are genetically identical with one another as well as with the parent. 90 (c) Statements I, II and IV are correct, but statement III is incorrect and can be corrected as l Ginger propagates vegetatively with the help of rhizome. Rhizomes are main underground stems which store food for perennation during unfavourable conditions. These have buds for the formation of new aerial shoots during favourable conditions. 91 (a) Statements II and IV are correct. But statements I and III are incorrect and can be corrected as l l Lifespans of organisms are not necessarily correlated with their sizes. A mango tree has a much storter lifespan as compared to a peepal tree. 93 (c) Statements I, II, IV and V are correct. Statement III is incorrect and can be corrected as In gymnosperms, the non-motile male gametes are carried to the female gamete through pollen tube. 94 (b) Statements III, IV and V are correct. Statements I and II are incorrect and can be corrected as l l Eichhornia drains oxygen from the water bodies which increases the mortality of fishes. Zingiber propagates vegetatively by rhizome (underground stem). 95 (d) Statements I and III are incorrect and can be corrected as l l The vegetative phase is of different durartion in different organisms. Bambusa differs from Strobilanthes kunthiana in the length of juvenile phase, but both plants are monocarpic. Rest of the statements are correct. 96 (a) Statements I, III and V are correct. Statements II and IV are incorrect and can be corrected as l l In both plants and animals, hormones are responsible for transitions between the three phases, i.e. juvenile, reproductive and senescent. The pre-fertilisation events include gametogenesis and gamete transfer. 104 (b) Statements I and II are correct. Statements III and IV are incorrect and can be corrected as l l Meiosis is required for the production of haploid gametes during sexual reproduction. External fertilisation is not a rule during sexual reproduction, it can occur internally also. Answers & Explanations 78 (c) Assertion is true, but Reason is false and it can be www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 18 105 (a) The term ‘clone’ cannot be applied to offspring 106 107 108 109 110 Answers & Explanations 111 112 formed by sexual reproduction because offspring do not possess exact copies of parental DNA. Offspring produced by sexual reproduction has half DNA from one parent and half from another parent, thus is not an exact copy of any one parent, i.e. it is not a clone. But there DNA is still similar to their parents DNA. (c) In female gamete of rice plant the chromosome number will be same as that of the male gamete (12). Zygote is formed by fertilisation of male and female gametes thus, the chromosome number will be 24 (2n). A seedling is young plant sporophyte developing out of embryo. So, chromosome number will be 24 (2n). Thus, option (c) is correct. (c) Unicellular organisms (like Amoeba and yeast) have a relatively simple body organisation. So, asexual mode of reproduction is common in them because by asexual reproduction unicellular organisms can multiply very fast. In Amoeba, it occurs by binary fission and in yeast by budding. (b) The appearance of vegetative propagules from the nodes of plants like sugarcane and ginger is due to the presence of meristematic cells at the nodes. These cells have the capacity of rapid cell division, thus are responsible for growth and development of tissues and organs in plants. (c) Statement in option (c) is correct. Dioecious is the term used to describe unisexual condition in plants and animals, e.g. Marchantia (plants) and cockroach (animals). (d) There is a large diversity in the biological world and each organism has evolved its own mechanism to multiply and produce offspring. The type of reproduction adopted by an organism depends on the organism’s habitat, its internal physiology, genetic makeup and several other factors. (b) Embryo development takes place after the event of fertilisation, i.e. fusion of male and female gametes (n) and results in the formation of zygote (2n). Thus, it is a post-fertilisation event. Rest of the events takes place before the occurrence of fertilisation and hence, are pre-fertilisation events. (c) Statements II and IV are true for both asexual and sexual reproduction. But gametic fusion and reduction division take place only in sexual reproduction. 114 (d) Option (d) is correct and can be explained as In a multicellular filamentous alga (e.g. Ulothrix), the sexual life cycle have meiotic division after the zygote (2n) formation. It mean meiosis in zygote will produce haploid spores or vegetative cells (n ) and when these vegetative cells undergo asexual reproduction the gametophyte or gametangia formed will be haploid (n ) too. 115 (b) Statements I and III are correct regarding external fertilisation. Statements II and IV are incorrect and can be corrected as l l A large number of gametes are released into the medium (water) to increase the chances of fertilisation. The chances of survival of offspring from external fertilisation are lesser than those of internal fertilisation as they face more risk from predators. 116 (a) Statements I and II are correct. Statements III and IV are incorrect and can be corrected as Gynoecium is the female part of the flower, a unit of which is called pistil. A pistil may have one or more than one carpels (monocarpellary, bicarpellary, etc). Each carpel may have more than one ovules. 119 (b) In sexual reproduction genetic variation is observed. In this mode of reproduction, gametes of two parents (opposite sex) having qualitatively different genetic composition participate in the reproductive process, (i.e. fusion of male and female gametes). This gives rise to a new individual having an entirely new genetic makeup. 120 (c) There is no natural death in single-celled organisms like Amoeba and bacteria. It is so, because of asexual reproduction, the body of parent is divided or distributed into daughter cells or offspring. In such organisms, reproduction occurs by cell division where the parent cell divides into two halves. 121 (b) Statement in option (b) is incorrect and can be corrected as Zoospores are asexually reproducing structures. Rest of the statements are correct. 122 (a) Shoot tip cells and microspore mother cells both are diploid in maize plant. If number of chromosomes in shoot tip cell is (2n) = 20, then number of chromosomes in microspore mother cell will be (2n) = 20. www.mediit.in CHAPTER > 02 Sexual Reproduction in Flowering Plants NEET Å Å KEY NOTES Sexual reproduction occurs in all flowering plants, i.e. angiosperms. It is the process of fusion of haploid gametes, resulting in the production of a diploid zygote. Which ultimately develops into new organism. Stamen, Microsporangium and Pollen Grain Different types of adaptations are shown in angiosperms by the diversified structures of the inflorescences, flowers and floral parts, to ensure the formation of the end products of sexual reproduction, i.e. the fruits and seeds. Stamen The male gametophyte includes the following parts Å It is the male reproductive unit of angiosperms. It consists of two parts n Flower Å Å It is the modified condensed shoot arising on the axil of small leaf-like structure called bract and consists of four whorls or floral appendages, attached on the receptacle. Of these, the two lower whorls, i.e. calyx and corolla are sterile and considered as non-essential/accessory/helping whorls and the two upper whorls, i.e. androecium and gynoecium are fertile and are considered as essential or reproductive whorls. Pre-fertilisation: Structures and Events Å Several hormonal and structural changes in plants lead to the differentiation and further development of the floral primordium. Å Inflorescences are formed which bear the floral buds and then the flowers. Å In the flower, the androecium (male reproductive part) and gynoecium (female reproductive part) differentiate and develop to form the male and female gametophyte. n The long and slender stalk called the filament. The terminal, generally bilobed structure called the anther. Å The proximal end of the filament is attached to the thalamus or the petal (i.e. epipetalous) of the flower. The number and length of the stamens are variable in flowers of different species. Å A typical angiospermic anther is a bilobed structure with each lobe having two theca (dithecous) and are separated by a longitudinal groove running lengthwise. Å In a cross section, the anther is a tetragonal structure consisting of four microsporangia located at the corners, two in each lobe. Later, the microsporangia develop and become pollen sacs, which are packed with pollen grains. Structure of Microsporangium Å A typical microsporangium is surrounded by four wall layers, i.e. the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers are protective in function and help in dehiscence of anther to release pollen grains. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 20 Å Tapetum (innermost layer) nourishes the developing microspores or pollen grains and the cells of tapetum possess dense cytoplasm and generally have more than one nucleus. Middle layers Exine Intine Pollen grain Å The vegetative cell is larger, has abundant reserve food material and a large nucleus, which is irregular in shape. Whereas, the generative cell is small, spindle-shaped and floats in the cytoplasm of the vegetative cell. Å Pollen grains are generally shed at this 2-celled stage in over 60% of angiosperms. In the remaining species, the generative cell divides mitotically and gives rise to two male gametes before pollen grains are shed (3-celled stage). Å Pollen grains of several plant species may cause severe allergies and bronchial infections leading to asthma, bronchitis, etc., e.g. Parthenium or carrot grass came to India as a contaminant with imported wheat, became ubiquitous in occurrence and caused pollen allergy. Å Pollen grains are rich in nutrients. In Western countries, large number of pollen products in the form of tablets and syrups are used to increase the performance of athletes and race horses. Å Viability of pollen depends on temperature and humidity. It varies from species to species, e.g. 30 minutes in case of wheat, rice and several months as in some members of Solanaceae, Rosaceae, Leguminosae, etc. Å It is possible to store pollen grains for years in liquid nitrogen (–196°C) in pollen banks for later use in plant breeding programmes. (b) When the anther is young, a group of compactly arranged homogenous cells called the sporogenous tissue occupies the centre of each microsporangium. Microsporogenesis Å Å Å Each cell of the sporogenous tissue is a potential Pollen Mother Cell (PMC) or microspore mother cell and can give rise to microspore tetrad. This process of formation of microspore from a pollen mother cell through the process of meiosis is called microsporogenesis. As the anthers mature and dehydrate, the microspores dissociate from one another and form tetrad and develop into pollen grains. Inside each microsporangium, several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther. In general, dehiscence of anther occurs through the rupture of the anther lobe walls, which causes the release of the pollen grains. Male Gametophyte (Pollen Grain) Å Å Å A pollen grain is a partly germinated microspore representing the male gametophyte. It is a haploid, uninucleate and minute spore produced in large numbers by meiosis in the microspore mother cell. They vary in their size, shape, colour, design, etc., from species to species. Pollen grains are generally spherical measuring about 25-50 micrometre in diameter. It has a two layered wall (also called sporoderm), outer hard layer exine is made up of sporopollenin. It is the most resistant organic material as it can withstand high temperature as well as strong acids and alkali. No known enzyme can degrade it. Thus, pollens are well-preserved as fossils. Pollen grains have prominent distal aperture for germination called germ pore, where sporopollenin is absent. The inner layer intine is thin and chiefly composed of cellulose and pectin. NEET Generative cell Vegetative cell (a) Transverse section of a young anther (b) Enlarged view of a microsporangium showing four wall layers Å Each mature pollen grain in angiosperms has two cells, the generative cell and vegetative cell. Epidermis Endothecium Middle layers Microspore mother cells Tapetum Connective Epidermis Endothecium Sporogenous tissue Tapetum (a) Å The Pistil, Megasporangium (Ovule) and Embryo Sac The female gametophyte includes the following parts Pistil Å The pistil or gynoecium represents the female reproductive part of the flower. It may consist of one pistil or carpel (monocarpellary), two carpels (bicarpellary), three carpels (tricarpellary) or many carpels (multicarpellary). Å Pistil may be syncarpous (i.e. more than one pistils are fused together) as in Papaver, Solanum, etc., or apocarpous, i.e. (carpels remain free) as in Michelia, rose, etc. Å A typical pistil consists of the hollow basal swollen ovary, the elongated style and the terminal stigma (serves as a landing platform for pollen grains). Inside the ovary, is the ovarian cavity (locule) in which placenta is located. Megasporangium (ovules) arises from placenta. KEY NOTES www.mediit.in 21 CHAPTER 02 > Sexual Reproduction in Flowering Plants Structure of Megasporangium (Ovule) Å Å Å n The ovule is an integumented megasporangium within which meiosis and megaspore formation takes place. It is attached to the placenta by means of a stalk called funicle. It develops into a seed after fertilisation. The junction between an ovule and funicle is called hilum, which later becomes a scar on the seed. n Each ovule has one or two protective envelops called integuments, which encircle the ovule except at the tip where a small opening called micropyle is located. Three cells present towards the micropylar end are grouped together and constitute the egg apparatus, i.e. two synergids and one egg cell. Three cells of the chalazal end are called the antipodals. The large central cell is formed by the fusion of 2 polar nuclei. Thus, a typical angiospermic embryo sac or female gametophyte at maturity consists of eight nuclei and seven cells. Chalazal end Antipodals The basal part of an ovule just opposite to micropyle is called chalaza. Enclosed within the integuments is a mass of cells called nucellus, whose cells are rich in reserve food materials. An ovule generally has a single embryo sac or female gametophyte, developed from a megaspore through reductional division and located within the nucellus. Polar nuclei Central cell Egg Synergids Megasporogenesis Å The process of formation of megaspores from Megaspore Mother Cell or MMC (diploid) is called megasporogenesis. Å It occurs inside the nucellus of the developing ovule of angiosperms. The process begins very early when nucellus is not completely surrounded by the integuments. Å The MMC (a large cell containing dense cytoplasm and a prominent nucleus) enlarges in size and divides by meiosis. It first divides transversely into two cells called megaspore dyad. Å These two cells again divide transversely forming a linear row of four haploid cells which is called megaspore tetrad or linear tetrad. Female Gametophyte (Embryo Sac) Å In general, the development of embryo sac is monosporic, e.g. in Polygonum. In this type of development, only one megaspore situated towards chalazal end remains functional, while the remaining three megaspores gradually degenerate and finally disappear. Å Following are the different stages in development of female gametophyte n n n n The functional haploid megaspore is the first cell of female gametophyte of angiosperms. Its nucleus undergoes mitotic division to form 2-nuclei that move to opposite poles forming 2-nucleate embryo sac. The 2-nucleate embryo sac undergoes two more sequential mitotic divisions giving rise to the 4-nucleate stage and later 8-nucleate stage of embryo sac. This stage comprises of a micropylar end and a chalazal end with four nuclei at each end. Six of the eight nuclei are surrounded by cell walls and get organised into cells. The remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell. Filiform apparatus Micropylar end A diagrammatic representation of mature embryo sac Pollination The transfer of pollen grains from the anther of the stamen to the receptive stigma of the carpel/pistil is called pollination. Depending upon the source of pollen grains, pollination is of following three types Å Autogamy (Self-pollination) It is the kind of pollination achieved within the same flower. The pollens from the anthers of a flower are transferred to the stigma of the same flower, e.g. wheat, rice, pea, etc. Å Plants show following adaptations for autogamy. n n Cleistogamous flowers These are closed flowers and their anthers and stigma lie close to each other, e.g. Viola (common pansy), Mirabilis, Commelina and Oxalis. Almost all the cleistogamous flowers are invariably autogamous as there is no chance of cross-pollination. Chasmogamous flowers These are opened flowers with exposed sex organs. On these, pollens from another flower can land on the stigma as well, e.g. Catharanthus and Mirabilis. Å Geitonogamy It is the kind of self-pollination where the pollen grains from the anther of a flower are transferred to the stigma of another flower borne on the same plant, but at different branches. It usually occurs in plants which show monoecious condition, e.g. Cucurbita. Å Xenogamy (Cross-pollination) It involves the transfer of pollen grains from the anther of one plant to the stigma of another plant. This is the only type of pollination which brings genetically different types of pollen grains to the stigma during pollination, e.g. papaya, maize, etc. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 22 Agents of Pollination Outbreeding Devices Pollination in plants occurs via various abiotic and biotic agents as follows These are developed by bisexual flowers to avoid self-pollination and promote cross-pollination because continuous self-pollination results in poor yield and poor quality of seeds. This phenomenon is called inbreeding depression. Such devices are 1. Abiotic agents of pollination are wind (anemophily) and water (hydrophily). (a) Wind pollinated flowers have Å Light and non-sticky pollen grains. Å Generally a single ovule in each ovary and numerous flowers packed into an inflorescence, e.g. corn cob. Well-exposed stamens and large feathery stigma to trap air-borne pollen grains. Å Wind pollination is common in grass, maize, date palm, etc. Å (b) Water pollination occurs in mostly monocotyledons (in about 30 genera). Some examples of water pollinated plants are Hydrilla, Vallisneria and Zostera. Å Å Å Å Self-sterility Unisexuality Chasmogamous flowers Å Protandry (Maturation of male parts prior to female parts) Å Protogyny (Maturation of female parts before male parts) Å Note In castor and maize, unisexuality prevents autogamy. In papaya, it prevents both autogamy and geitonogamy. Pollen-Pistil Interaction Å The female flower reaches the surface of water by the long stalk and pollen grains are released onto the surface of water, e.g. Vallisneria. It involves pollen recognition followed by inhibition of pollen (sexual incompatibility) or promotion of pollen (sexual compatibility). Å In most of the water pollinated species, pollen grains are protected from wetting by mucilaginous covering. Pistil accepts the compatible pollen of the same species and rejects the incompatible pollen either of the same species or of other species. Å After compatible pollination, the pollen grain germinates and produces pollen tube (carries two male gametes) which moves through the style and reaches to the egg, which is known as ‘siphonogamy’ in angiosperms. Insect pollinated flowers are generally large, colourful, fragrant and rich in nectar. Å The pollen grains and stigmatic surface are sticky. Å The animal pollinated flowers offer certain rewards to the pollinators. Some of them are Å Å It consists of all the events from the deposition of pollen on stigma to entry of pollen tube into the ovule. Å n Dichogamy (Production of male and female reproductive parts at different times) Å In majority of aquatic plants, the flowers emerge above the level of water and are pollinated by insects or wind, e.g. water hyacinth and water lily. 2. Biotic agents of pollination are insects (entomophily), bats (chiropterophily), snails (malacophily), birds (ornithophily) etc. n Å Artificial Hybridisation Å It is the crossing of different species to generate a progeny containing all the desirable characters. These are commercially superior varieties. Å It is used for crop improvement programmes. This process involves Emasculation anther removal before dehiscence. Bagging covering emasculated flower in a bag to prevent its contamination by unwanted pollen grains. These offer nectar and (edible) pollen grains. Some species provide safe place for laying eggs, e.g. Amorphophallus and Yucca. A relationship exists between a species of moth and the plant Yucca, where both the species cannot complete their life cycles without each other. The moth deposits its eggs in the locule of the ovary and the flower, in turn, gets pollinated by the moth. The larvae of the moth come out of the egg as the seeds start developing. Many insects may consume pollen or the nectar without bringing about pollination. Such floral visitors are referred to as pollen/nectar robbers. NEET n n Å After the maturity of the stigma of the bagged flowers, collected pollen grains are dusted over it. The flowers are then rebagged at fruits are allowed to develop. Double Fertilisation It occurs after the pollen tube reaches the ovary. It is the characteristic of angiosperms. Å The pollen tube releases two male gametes into the cytoplasm of a synergid. KEY NOTES www.mediit.in 23 CHAPTER 02 > Sexual Reproduction in Flowering Plants Å One of the male gamete fuses with egg cell (syngamy), which results in the formation of zygote. Å The second male gamete fuses with the two polar nuclei to form a triploid Primary Endosperm Nucleus (PEN). This is called triple fusion. Since, two fusions, i.e. syngamy and triple fusion occur in an embryo sac, this is called double fertilisation. Central cell after the triple fusion called as Primary Endosperm Cell (PEC) develops into the endosperm and zygote develops into an embryo. Å Å Post-fertilisation : Structures and Events n n Seed Å Å Å Å Endosperm Å Å It is a mass of nutritive cell produced as a result of triple fusion through mitotic division. On the basis of development, it is of three types In nuclear type, which is a common method, the Primary Endosperm Nucleus (PEN) undergoes repeated mitotic division without cytokinesis. At this stage, the endosperm is called free- nuclear endosperm. In cellular type, cell wall formation occurs and the endosperm becomes cellular. The number of free nuclei formed before cellularisation varies greatly, e.g. in coconut the water is free nuclear endosperm and surrounding white kernel is cellular endosperm. In helobial type endosperm formation, one half of endosperm is nuclear type and other half is cellular type. n Å n n Fruits Å n Embryo It develops at the micropylar end of the embryo sac where the zygote is situated. Å Embryo formation occurs when certain amount of endosperm is formed, because endosperm provides nutrition for embryo development. Ovary develops into fruit and ovule matures into seeds. The wall of ovary becomes wall of fruit, i.e. pericarp. In true fruits, ovary contributes to fruit formation. Fruits may be fleshy such as, guava, orange, mango or dry such as groundnut, mustard, etc. In false fruits, thalamus (swollen end of stems that bear floral parts) also contributes to fruit formation, e.g. apple, cashewnut, etc. Parthenocarpic fruits develop without fertilisation and are seedless, e.g. banana. Seedless fruits can be reproduced artificially through the application of growth hormones. n n Å It is the fertilised ovule formed inside the fruits. It consists of seed coat (hardened ovule integuments), cotyledons and an embryonal axis. Two types of mature seeds are Non-albuminous in which endosperm is completely consumed, e.g. in pea and groundnut. Albuminous that retain part of endosperm, e.g. wheat, maize and barley. In some seeds, remnants of nucellus are persistant which is called perisperm, e.g. black pepper and beet root. Micropyle of the ovule remains as the small pore in the seed coat. It facilitates the entry of oxygen and water into seed during germination. Dormancy In this condition, water content reduces, seed become dry, metabolic activities of embryo slow down and the seed may enter into a state of inactivity called dormancy. If conditions are not favourable seed will not germinate and it may germinate, if conditions are favourable. n Development of endosperm, embryo, maturation of ovule into seed and ovary into fruit are collectively termed as post-fertilisation events. Å Embryonal axis has the radicle on its lower end (hypocotyl), the radicle is covered by an undifferentiated sheath called coleorhiza. At the upper end (epicotyl), the embryonal axis has plumule. It is covered by a hollow foliar sheath called coleoptile. n n n n Å Zygote divides by mitosis and forms proembryo. This results in the formation of globular and heart-shaped embryo that finally becomes horse shoe-shaped (mature embryo) having cotyledon. Apomixis and Polyembryony Å Dicot embryo consists of two cotyledons and an embryonal axis between them n n Å n The part of embryonal axis above the level of cotyledons is the epicotyl which becomes plumule (shoot). The part of embryonal axis below the level of cotyledons is the hypocotyl which becomes radicle or root tip. Monocot embryo consists of only one cotyledon (called scutellum in grass family), e.g. rice, maize plants, etc. Å Apomixis is the special mechanism to produce seeds without fertilisation, e.g. grass and is a form of asexual reproduction that mimics sexual reproduction and is useful for the hybrid industry. The modes by which apomictic seeds can be produced are agamospermy, adventive embryony, etc. Polyembryony is the presence of more than one embryo in a seed. In many Citrus and Mangifera varieties, some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into embryos. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 24 Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Flower and Development of Gametes 1 Identify A to G in following figure and answer accordingly. (a) pollen (c) anther E D F 4 The terminal structure of stamen is called (b) filament (d) All of these 5 The lengthwise running groove on anther which separate theca is called G C (a) (b) (c) (d) B rupture line line of dehiscence suture of anther None of the above 6 Number of microsporangia in an angiospermic A anther is (a) A–Ovary, B–Filament, C–Sepal, D–Petal, E–Style, F–Stigma, G–Anther (b) A–Sepal, B–Ovary, C–Petal, D–Filament, E–Anther, F–Stigma, G–Style (c) A–Ovary, B–Sepal, C–Filament, D–Petal, E–Anther, F–Stigma, G–Style (d) A–Petal, B–Anther, C–Stigma, D–Style, E–Filament, F–Sepal, G–Ovary 2 Find odd one out. (a) 1 (b) 2 (a) pollens (c) megagametes (d) 4 (b) microgametes (d) pollen sac 8 Identify A to E in the following diagram. A B C JIPMER 2019 (b) Stigma (d) Ovary (a) Stamen (c) Style (c) 3 7 Microsporangium develops into D 3 Identify A to D in the following diagram. E D C B A (a) A – Filament (stalk) , B – Pollen sac, C – Pollen grain, D – Line of dehiscence (b) A – Filament (stalk), B – Pollen sac, C – Line of dehiscence, D – Pollen grain (c) A – Line of dehiscence, B – Filament (stalk) , C – Pollen sac, D – Pollen grains (d) A – Filament (stalk), B – Line of dehiscence, C – Pollen sac, D – Pollen grains (a) A–Tapetum, B–Microspore mother cell, C–Middle layer, D–Endothecium, E–Epidermis (b) A–Epidermis, B–Middle layer, C–Microspore mother cell, D–Tapetum, E–Endothecium (c) A–Middle layer, B–Epidermis, C–Tapetum, D–Microspore mother cell, E–Endothecium (d) A–Epidermis, B–Endothecium, C–Middle layer, D–Microspore mother cell, E–Tapetum 9 The innermost layer of microsporangium is (a) tapetum (c) middle layer (b) endothecium (d) epidermis 10 Centre of each microsporangium is occupied by (a) (b) (c) (d) sporogenous tissue tapetum central tissue microspore mother cell www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 11 Identify A to E in the following diagram. 25 18 Intine is made up of (a) cellulose (c) Both (a) and (b) A B C D F E (a) A–Epidermis, B–Endodermis, C–Connective, D–Sporogenous tissue, E–Middle layers, F–Tapetum (b) A–Endodermis, B–Connective, C–Epidermis, D–Tapetum, E–Sporogenous tissue, F–Middle layers (c) A–Tapetum, B–Middle layers, C–Sporogenous tissue, D–Connective, E–Endodermis, F–Epidermis (d) A–Connective, B–Epidermis, C–Endothecium, D–Sporogenous tissue, E–Tapetum, F–Middle layers 12 The outermost wall layer of microsporangium in anther is (a) endothecium (c) middle layer (b) tapetum (d) epidermis 13 Which of the following perform microsporogenesis? (a) Microspore mother cell (b) Pollen mother cell (c) Both (a) and (b) (d) None of these 14 The process of formation of microspores from pollen mother cell through … A… is called … B... . Microspores are arranged in … C … . As the anthers matures and dehydrate, microspores develop into the …D… . Fill in the blanks A to D. (a) A–pollen grains, B–microspore tetrad, C–microsporogenesis, D–meiosis (b) A–microspore tetrad, B–microsporogenesis, C–meiosis, D–pollen grains (c) A–microsporogenesis, B–microspore tetrad, C–pollen grain, D–meiosis (d) A–meiosis, B–microsporogenesis, C–microspore tetrad, D–pollen grains 15 Microspore tetrad (pollen grains) is the result of (a) mitotic cell division (c) Both (a) and (b) (b) meiotic cell division (d) None of these 16 Dehiscence of anther in mesophytes is caused by (a) hydration of anthers (c) mechanical injury (b) dehydration of anthers (d) None of these 17 Pollens have two prominant walls which are …A… 19 Exine of pollen is made up of (a) (b) (c) (d) sporopollenin sporogenous tissue spongiform tissue inorganic material 20 Patterns and designs of exine of pollen grains are the characteristic features of (a) species of plant (c) order of plants (b) genus of plants (d) None of these 21 Hardest substance in plant kingdom is (a) saple (c) sporopollenin JIPMER 2019 (b) corolla (d) anther 22 The sporopollenin is non-degradable because (a) (b) (c) (d) it can withstand strong acids it is resistant at very high temperature no enzyme degrade it All of the above 23 Which of the following has proved helpful in preserving pollen as fossils? (a) Oil content (c) Pollenkitt NEET 2018 (b) Cellulosic intine (d) Sporopollenin 24 The functions of germ pore is/are (a) (b) (c) (d) emergence of radicle absorption of water for seed germination initiation of pollen tube All of the above 25 Identify the structures marked A to F in the given diagram. B A C E D F (a) A–Asymmetric nucleus, B–Nucleus, C–Generative cell, D–Vegetative cell, E–Pollen, F–Pollen tetrad (b) A–Pollen tetrad, B–Pollen, C–Generative cell, D–Vegetative cell, E–Asymmetric spindle, F–Nucleus (c) A–Pollen tetrad, B–Vacuole, C–Nucleus, D–Asymmetric spindle, E–Vegetative cell, F–Generative cell (d) A–Vacuole, B–Nucleus, C–Pollen tetrad, D–Vegetative cell, E–Asymmetric spindle, F–Generative cell 26 When the pollen grain is mature, it contains two cells, and …B… . Here A and B refers to the … A … and … B …. (a) (b) (c) (d) (a) (b) (c) (d) A–intine, B–protein coat A–exine, B–intine A–sporopollenin, B–intine A–sporopollenin, B–exine (b) pectin (d) protein A–generative cell, B–spore mother cell A–vegetative cell, B–spore mother cell A–spore mother cell, B–male gamete A–vegetative cell, B–generative cell www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 26 27 To achieve 3-celled stage in angiosperms, which cell 35 Identify A to I in the given diagram. of the pollen grain divides to form two male gametes ? (a) (b) (c) (d) A B C D E NEET 2018 Vegetative cell Generative cell Microspore mother cell None of the above F G H 28 60% of the angiosperms shed their pollens at the (a) 2-celled stage (c) 4-celled stage (b) 3-celled stage (d) 1-celled stage 29 Male gametophyte in angiosperms produces I CBSE-AIPMT 2015 (a) (b) (c) (d) two sperms and a vegetative cell single sperm and a vegetative cell single sperm and two vegetative cell three sperms 30 Pollen tablets are available in the market for CBSE-AIPMT 2014 (a) in vitro fertilisation (c) supplementing food (b) breeding programmes (d) ex situ conservation 31 Pollen grains can be stored for several years in liquid nitrogen having temperature of (a) – 196°C (b) – 80°C (c) – 120°C NEET 2018 (d) – 160°C 32 In the given diagram of pistil, in which part fertilisation takes place? (a) A–Chalazal end, B–Embryo sac, C–Nucellus, D–Inner integuments, E–Outer integuments, F–Micropylar pole, G–Micropyle, H–Funicle, I–Hilum (b) A–Inner integuments, B–Nucellus, C–Embryo sac, D–Chalazal end, E–Hilum, F–Funicle, G–Micropyle, H–Micropylar end, I–Outer integuments (c) A–Hilum, B–Funicle, C–Micropyle, D–Micropylar pole, E–Outer integuments, F–Inner integuments, G–Nucellus, H–Embryo sac, I–Chalazal pole (d) A–Micropylar end, B–Micropyle, C–Funicle, D–Hilum, E–Outer integuments, F–Inner integuments, G–Nucellus, H–Embryo sac, I–Chalazal end 36 The stalk which joins ovule and placenta is called (a) funicle (c) chalaza A (b) hilum (d) micropyle 37 The ovule of an angiosperm is technically B equivalent to NEET 2016 (b) megasporophyll (a) megasporangium (c) megaspore mother cell (d) megaspore 38 An ovule is a C D (a) D (b) C (c) B (d) A 33 Identify the type of pistil in the diagram. (a) (b) (c) (d) differentiated megasporangium dedifferentiated megasporangium integumented megasporangium redifferentiated megasporangium 39 Chalazal pole is present Stigma (a) (b) (c) (d) opposite to micropyle at the origin of integuments opposite to nucellus near the embryo sac 40 Mass of cells enclosed by integuments is called (a) (b) (c) (d) (a) nucellus (c) ova Multicarpellary, apocarpous Multicarpellary, syncarpous Multicarpellary, pistillate Monocarpellary, apocarpous 41 Embryo sac is also called 34 Identify the type of pistil in the diagram alongside. (a) (b) (c) (d) Monocarpellary, syncarpous Monocarpellary, apocarpous Multicarpellary, syncarpous Multicarpellary, apocarpus (b) embryo (d) pollen Carpels (a) female gamete (c) female gametophyte (b) synergids (d) egg of angiosperm 42 Megasporogenesis is (a) (b) (c) (d) formation of fruits formation of seeds formation of megaspores Both (b) and (c) www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 43 Megaspore mother cell is found near the region of (a) micropyle (c) nucellus (a) (b) (c) (d) 50 Identify the labelling of given diagrams. (b) chalaza (d) integuments 44 In majority of angiosperms egg has a filiform apparatus there are numerous antipodal cells reduction division occurs in the megaspore mother cells a small central cell is present in the embryo sac 45 In angiosperms, microsporogenesis and (a) (b) (c) (d) CBSE-AIPMT 2015 occur in anther form gametes without further divisions involves meiosis occur in ovule 46 Functional megaspore in an angiosperm develops into (a) ovule (c) embryo sac NEET 2017 (b) endosperm (d) embryo 47 Which is the most common type of embryo sac in angiosperms? (a) (b) (c) (d) NEET (Odisha) 2019 Tetrasporic with one mitotic stage of divisions Monosporic with three sequential mitotic divisions Monosporic with two sequential mitotic divisions Bisporic with two sequential mitotic divisions A–MMC, B–Megaspore dyad, C–Nucellus, D–Nucleus A–Nucellus, B–Megaspore dyad, C–Nucellus, D–MMC A–Nucellus, B–MMC, C–Nucellus, D–Megaspore dyad A–MMC, B–Nucellus, C–Megaspore dyad, D–Nucleus 51 Identify A to E in the diagram given below. (a) A–Antipodal, B–2 polar nuclei, C–Central cell, D–Egg, E–Synergids (b) A–Antipodal, B–Central cell, C–2 polar nuclei, D–Egg, E–Synergids (c) A–2 polar nuclei, B–Central cell, C–Antipodal cell, D–Egg, E–Synergids (d) A–Synergids, B–Egg, C–Central cell, D–2 polar nuclei, E–Antipodal cell (a) 1–1–2–3 (c) 2–1–1–3 49 Identify A to F in the diagram given below. A B C D E (b) 2–1–3–2 (d) 3–2–1–2 53 Identify A to F in the diagram given below. Degeneration of three cells B (a) (b) (c) (d) central cell → antipodal cell follows the order (b) unisporic (d) disporic A D B 52 In embryo sac, the number of synergid → egg cell → 48 Single megasporic development is called (a) single sporic (c) monosporic C A NEET 2016 megasporogenesis 27 F Only one remains functional E D C B C A F E D (a) A–Mitosis, B–Meiosis-I, C–Meiosis-II, D–Mitosis, E–Meiosis, F–Meiosis (b) A–Meiosis-I, B– Meiosis-II, C–Mitosis, D–Mitosis, E–Mitosis, F–Embryo sac (c) A–Embryo, B–Meiosis-I, C–Meiosis-II, D–Mitosis, E–Mitosis, F–Mitosis (d) A–Mitosis, B–Mitosis, C–Mitosis, D–Meiosis, E–Meiosis, F–Meiosis (a) A–Egg, B–Filiform apparatus, C–Synergid, D–Antipodals, E–Polar nuclei, F–Central cell (b) A–Egg, B–Synergid, C–Filiform apparatus, D–Antipodals, E–Central cell, F–Polar nuclei (c) A–Central cell, B–Egg, C–Synergid, D–Antipodals, E–Filiform apparatus, F–Polar nuclei (d) A–Filiform apparatus, B–Synergid, C–Egg, D–Central cell, E–Polar nuclei, F–Antipodals 54 Filiform apparatus are (a) (b) (c) (d) special cellular thickenings at antipodal cell special cellular thickenings at the micropylar end special cellular thickenings at synergid cells special cellular thickenings at nuclear end www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 28 59 Egg apparatus consists of 55 Function of filiform apparatus is to CBSE-AIPMT 2014, 08 (a) recognise the suitable pollen at stigma (b) stimulate division of generative cell (c) produce nectar (d) guide the entry of pollen tube (b) 7 (c) 6 chalazal end are called (d) 5 (a) nucellar cells (c) antipodal cells 57 How many cells are found in female gametophyte? (a) 6 (c) 7 (b) 8 (d) 5 (b) synergids (d) None of these 61 In an angiospermic anatropous ovule, the embryo sac contains certain cells at the micropylar end. These are called 58 Two nuclei within a single cell is (a) antipodal cell (c) central cell 2 synergids + 2 eggs 2 synergids + 2 eggs 2 synergids + 1 egg 2 synergids + 4 eggs 60 In an embryo sac of anatropous ovule, cells present at 56 How many nuclei are found in female gametophyte? (a) 8 (a) (b) (c) (d) (b) chalazal cell (d) synergid cell (a) synergids (c) nucellar cells (b) antipodal cells (d) None of these TOPIC 2 ~ Pollination 68 Geitonogamy involves 62 Autogamy stands for (a) (b) (c) (d) 63 Cleistogamous flowers are strictly autogamous because they remain (a) (b) (c) (d) always open always close always fragrance are brighty coloured 69 Transfer of pollen grains from the anther to stigma of another flower of different plant is called (a) geitonogamy (c) chasmogamy 64 Identify the type of flower A and B. (a) A–Cleistogamous; B–Chasmogamous (b) A–Homogamous; B–Heterogamous (c) A–Chasmogamous; B–Cleistogamous (d) A–Heterogamous; B–Homogamous flowering plant is/ are (a) water (c) Both (a) and (b) (b) wind (d) None of these 71 Characteristic of wind pollinated pollens is, they are B open flower closed flower large flower geitonogamy flower (a) (b) (c) (d) non-sticky light produced in large number All of the above 72 The feathery long stigma is found in (a) rice (b) maize (c) sugarcane (d) None of these 73 Flowers, which have single ovule in the ovary and are 66 Advantage of cleistogamy is NEET 2013 (a) water (a) lilies CBSE-AIPMT 2012 (b) Zostera (d) Fig (b) bee (c) wind 74 Wind pollination is common in 67 Even in the absence of pollinating agents seed-setting is assured in packed into inflorescence are usually pollinated by NEET 2017 (a) higher genetic variability (b) more vigorous offspring (c) no dependence on pollinators (d) vivipary (a) Commelina (c) Salvia (b) xenogamy (d) cleistogamy 70 The most common abiotic pollinating agency in A 65 In chasmogamy pollination takes place in (a) (b) (c) (d) CBSE-AIPMT 2014, 10, 1994 (a) fertilisation of a flower by the pollen from another flower of the same plant (b) fertilisation of a flower by the pollen from the same flower (c) fertilisation of a flower by the pollen from a flower of another plant in the same population (d) fertilisation of a flower by the pollen from a flower of another plant belonging to a distant population pollination in same flower pollination between different plants pollination in two flowers of same plant division in embryo (b) grasses (d) bat CBSE-AIPMT 2015, 14 (c) orchids (d) legumes 75 Pollination in water hyacinth and water lily is brought about by the agency of (a) water (c) birds NEET 2016 (b) insects or wind (d) bats www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 76 What type of pollination takes place in Vallisneria? NEET 2019 (a) Pollination occurs in submerged condition by water (b) Flowers emerge above surface of water and pollination occurs by insects (c) Flowers emerge above water surface and pollen is carried by wind (d) Male flowers are carried by water currents to female flowers at the surface of water 77 Pollen grain of water pollinated plants are coated by covering to prevent it from wetting (a) mucilage (c) exine (b) cuticle (d) intine 78 Wind pollinated and water pollinated flowers (a) (b) (c) (d) are colourful are non-colourful are small in size produce nectar JIPMER 2018 anemophily entomophily malacophily zoophily 80 Attractants and rewards are required for (a) (b) (c) (d) NEET 2017 anemophily entomophily hydrophily cleistogamy 81 Which one of the following plants shows a very close relationship with a species of moth, where none of the two can complete its life cycle without the other? NEET 2018 (a) Banana (c) Hydrilla (b) Yucca (d) Viola 82 Continued self-pollination results in (a) (b) (c) (d) 85 In which of the following, both autogamy and geitonogamy are prevented? NEET (Odisha) 2019, CBSE-AIPMT 2012 (a) Wheat (b) Papaya (c) Castor (d) Maize 86 Identify A to F in the given diagram. (a) A–Pollen tube, B–Ovary, C–Ovule, D–Antipodal cell, E–Pollen grain, F–Polar nuclei (b) A–Polar nuclei, B–Antipodal cell, C–Ovule, D–Ovary, E–Pollen tube, F–Pollen grain (c) A–Pollen grain, B–Pollen tube, C–Ovary, D–Ovule, E–Antipodal cell, F– Polar nuclei (d) A–Antipodal cell, B–Ovule, C–Ovary, D–Polar nuclei, E–Pollen grain, F–Pollen tube A B C E D F 87 Diagram showing entry of pollen tube to the embryo 79 Pollenkitt is present in (a) (b) (c) (d) 29 inbreeding depression out breeding depression hybrid vigour better result in offspring sac. Identify A to G in the diagram. (a) A–Synergid, B–Filiform apparatus, C–Male gamete, F A D–Plasma membrane, G E–Central cell, F–Egg nucleus, G–Vegetative B nucleus (b) A–Filiform apparatus, C B–Central cell, C–Egg nucleus, D–Vegetative D nucleus, E–Male gamete, E F–Synergid, G–Plasma membrane (c) A–Plasma membrane, B–Synergid, C–Filiform apparatus, D–Male gametes, E–Vegetative nucleus, F–Central cell, G–Egg nucleus (d) A–Central cell, B–Egg nucleus, C–Vegetative nucleus, D–Male gametes, E–Synergid, F–Plasma membrane, G-Filiform apparatus 88 Diagram showing discharge of gametes in the egg apparatus. Identify A, B and C. A 83 Device to discourage self-pollination or increase B cross-pollination is (a) pollen release and stigma receptivity are not synchronised (b) anther and stigma placed at different position (c) same height of stamen and stigma (d) Both (a) and (b) C 84 A dioecious flowering plant prevents both NEET 2017 (a) (b) (c) (d) autogamy and xenogamy autogamy and geitonogamy geitonogamy and xenogamy cleistogamy and xenogamy (a) (b) (c) (d) A–Polar nuclei, B–Female gametes, C–Synergid cell A–Male gametes, B–Synergid cell, C–Polar nuclei A–Synergid cell, B–Male gametes, C–Polar nuclei A–Polar nuclei, B–Male gametes, C–Synergid cell www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 30 91 The process of removal of anther from the flower bud 89 Generally pollen tube enters through (a) (b) (c) (d) before it dehisces is called as micropylar region antipodal region chalazal end nuclear region (a) emasculation (c) embryo rescue 90 The ability of the pistil to recognise the pollen followed by its acceptance or rejection is the result of a continuous dialogue between pollen grain and the pistil. Which of the following chemicals mainly takes part in this interaction. (a) Nucleotides (c) Minerals (b) Proteins (d) Lipid or Inulin AIIMS 2019 (b) bagging (d) budding 92 For artificial hybridisation experiment in bisexual flower, which of the sequence is correct? (a) Bagging → Emasculation → Cross-pollination → Rebagging (b) Emasculation→ Bagging → Cross-pollination → Rebagging (c) Cross-pollination → Bagging → Emasculation → Rebagging (d) Self-pollination → Bagging → Emasculation → Rebagging TOPIC 3 ~ Double Fertilisation and Development of Endosperm 93 Double fertilisation is NEET 2018 (a) fusion of two male gametes with one egg (b) fusion of one male gamete with two polar nuclei (c) fusion of two male gametes of pollen tube with two different eggs (d) syngamy and triple fusion 94 Double fertilisation is exhibited by (a) gymnosperms (c) fungi 95 I. III. V. VII. 96 What is the fate of the male gametes discharged in the NEET 2019 (a) All fuse with the egg (b) One fuses with the egg, other(s) fuse(s) with synergid nucleus (c) One fuses with the egg and other fuses with central cell nuclei (d) One fuses with the egg other(s) degenerate(s) in the synergid 97 Find out A, B and C in the flowchart given below. B n 2n A–Embryo, B–Male gamete, C–Female gamete A–Male gamete, B–Female gamete, C–Embryo A–Female gamete, B–Embryo, C–Male gamete A–Male gamete, B–Embryo, C–Female gamete 99 How many number of nuclei are involved in (b) II, IV, VI and VII (d) II, IV, III and I A B n C (a) (b) (c) (d) Out of the seven names given above, find out haploid cells. synergid? A n 2n II. Egg cell IV. Polar nuclei VI. Nucellar cell (a) I, II, IV and V (c) I, II, III and V 98 Find out A, B and C in the flowchart given below. NEET 2017 (b) algae (d) angiosperms Antipodal cell Synergid cell Male gamete Central cell (c) A–Male gamete, B–Polar nuclei, C–Endosperm (d) A–Female gamete, B–Endosperm, C–Male gamete C 3n (a) A–Female gamete, B–Male gamete, C–Endosperm (b) A−Endosperm, B–Female gamete, C–Male gamete fertilisation? (a) 1 (b) 1 + 1 (c) 2 + 1 (d) None of these 100 The total number of nuclei involved in triple fusion is/are (a) 2 (b) 3 (c) 4 (d) 1 101 Syngamy and triple fusion is called …A… . The central cell becomes …B… develop into …C… and zygote develops into …D… . A, B, C and D in the above statements are (a) A–fusion, B–haploid, C–diploid cell, D–embryo (b) A–double fertilisation, B–PEC, C–endosperm, D–embryo (c) A–embryo, B–endosperm, C–PEC, D–diploid cell (d) A–PEC, B–endosperm, C–syngamy, D–fertilisation 102 If stem has 2n = 10 number of chromosomes then find out A – number of chromosome in endosperm. B – number of chromosome in egg cell. C – number of chromosome in polar nuclei, respectively. (a) 15, 15, 20 (c) 15, 5, 10 (b) 10, 15, 20 (d) 10, 5, 15 www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants (a) A–Degenerating antipodal cell, B–Primary endosperm nucleus, C–Primary endosperm cell, D–Synergid cell, E–Zygote (b) A–Synergid cell, B–Antipodal cell, C–Zygote, D–Endosperm cell, E–Chalazal cell (c) A–Degenerating synergids, B–Zygote, C–Primary endosperm cell, D–Primary endosperm nucleus, E–Degenerating antipodal cell (d) A–Zygote, B–Synergid, C–Primary endosperm cell, D–Primary endosperm nucleus, E–Degenerating antipodal cell 103 If endosperm has 36 number of chromosomes then find out the chromosome number of male and female gamete. (a) 18, 18 (b) 17, 18 (c) 20, 20 (d) 12, 12 104 PEC (Primary Endosperm Cell) is formed (a) after triple fusion (b) before triple fusion (c) at the time of syngamy (d) always persisted 105 In an angiosperm, male plant is diploid and female plant is tetraploid then endosperm will be (a) haploid (c) tetraploid (b) triploid (d) pentaploid 106 In angiosperm, pollen tube librates their male gametes 108 Out of the following choose the post-fertilisation event(s). into the (a) central cell (c) egg cell 31 (a) Endospermogenesis (c) Both (a) and (b) (b) antipodal cell (d) synergids 107 In the given fertilised embryo sac, identify A to E. (b) Embryogenesis (d) Megasporogenesis 109 The morphological nature of the edible part of coconut is A NEET 2017 (a) perisperm (c) endosperm B (b) cotyledon (d) pericarp 110 Coconut water from a tender coconut is (a) (b) (c) (d) C D immature embryo free-nuclear endosperm innermost layers of the seed coat degenerated nucellus CBSE-AIPMT 2015 111 Endosperm is consumed by developing embryo in the seed of E (a) pea (c) coconut (b) maize (d) castor TOPIC 4~ Embryo, Seed and Fruit Formation 112 Identify the different stages in embryogenesis in the given diagram A, B, C, D, E, F and G. F E G A (a) (b) (c) (d) B C D A–2-celled stage, B–Heart-shaped embryo, C–Globular embryo, D–Mature embryo, E–Radicle, F–Suspensor, G–Cotyledon A–2-celled stage, B–Mature embryo, C–Heart-shaped embryo, D–Globular embryo, E–Cotyledon, F–Radicle, G–Suspensor A–2-celled stage, B–Globular embryo, C–Heart-shaped embryo, D–Mature embryo, E–Suspensor, F–Radicle, G–Cotyledon A–Mature embryo, B–Heart-shaped embryo, C–Globular embryo, D–2-celled stage, E–Suspensor, F–Cotyledon, G–Radicle www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 32 113 Identify the A to E in the following diagram of typical dicot embryo. A B C D E (a) A–Cotyledons, B–Hypocotyl, C–Plumule, D–Root cap, E–Radicle (b) A–Radicle, B–Root cap, C–Plumule, D–Hypocotyl, E–Cotyledons (c) A–Hypocotyl, B–Cotyledons, C–Plumule, D–Radicle, E–Root cap (d) A–Plumule, B–Cotyledons, C–Hypocotyl, D–Radicle, E–Root cap 114 In figure given below, find out the type of seed and identify coleoptile, coleorhiza and epiblast. A 116 A typical dicotyledonous embryo consist of an …A… axis and …B… cotyledons. The portion of embryonal axis above the level of cotyledons is …C… which terminates with the …D… or stem tip. A, B, C and D in the above statement are (a) (b) (c) (d) A–plumule, B–epicotyl, C–cotyledons, D–embryonal A–embryonal, B–two, C–epicotyl, D–plumule A–embryonal, B–epicotyl, C–cotyledons, D–plumule A–embryonal, B–plumule, C–cotyledons, D–epicotyl 117 The cylindrical portion below the cotyledons is …A… that terminates to …B… and its tip is called …C… . A, B and C here refers to (a) (b) (c) (d) A–radicle, B–hypocotyl, C–root cap A–root cap, B–radicle, C–hypocotyl A–hypocotyl, B–root cap, C–radicle A–hypocotyl, B–radicle, C–root cap 118 The wheat grain has an embryo with one large, shield-shaped cotyledon known as CBSE-AIPMT 2015 (a) epiblast (c) scutellum (b) coleorhiza (d) caleoptile 119 Number of seeds are equal to the B C D (a) number of ovules (c) Both (a) and (b) (b) number of ovaries (d) None of these 120 Persistent nucellus in the seed is known as NEET 2019 (a) perisperm (b) hilum (c) tegmen (d) chalaza 121 Which is most crucial for seed storage? E F G (a) (b) (c) (d) (a) (b) (c) (d) Dehydration and dormancy Endosperm and water Least amount of development Endosperm in large quantity 122 True fruit is directly derived from Monocots–A , B and C Dicots–F, A and C Monocots–B, G and D Dicots–D, E and A (a) stem (c) ovary (b) root (d) None of these 123 False fruit is a fruit in which 115 Identify the parts labelled as A to D in structure of seed given below. (a) (b) (c) (d) only ovary take part in fruit development only embryo take part in fruit development only chalazal cells take part in fruit development ovary and other floral part are included in fruit development 124 Thalamus contributes in the fruit formation in A B C D (a) (b) (c) (d) A–Coleoptile, B–Plumule, C–Radicle, D–Coleorhiza A–Plumule, B–Coleoptile, C–Coleorhiza, D–Radicle A–Coleorhiza, B–Radicle, C–Plumule, D–Coleoptile A–Radicle, B–Plumule, C–Coleoptile, D–Coleorhiza (a) apple (c) cashewnut (b) strawberry (d) All of these 125 The world’s oldest viable seed, excavated from Arctic Tundra is of (a) lupine (b) Ficus (c) date palm (d) Phoenix 126 Viability of date palm (Phoenix dactylifera) seed is (a) 2000 yrs (c) 500 yrs (b) 1000 yrs (d) 100 yrs www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 33 TOPIC 5 ~ Apomixis and Polyembryony 127 Seed formation without fertilisation in flowering plants involves the process of (a) budding (c) apomixis 131 Vegetative/Asexual reproduction and apomixis are common to each other in NEET 2016 (a) (b) (c) (d) (b) somatic hybridisation (d) sporulation 128 Type of cell division takes place in apomixis is (a) reductional (c) Both (a) and (b) (b) meiosis (d) mitosis 132 Nucellar polyembryony is reported in (a) Gossypium (c) Brassica 129 Ovules contain many embryo in (a) Citrus (c) mango (b) apple (d) Both (a) and (c) (b) Triticum (d) Citrus 133 Apomictic embryos in Citrus arise from (a) (b) (c) (d) 130 Occurrence of more than one embryo is called (a) polyembryony (c) parthenogenesis type of cell division clone nature of offspring Both (a) and (b) only in dicot plant (b) embryony (d) fertilisation synergids maternal sporophytic tissue in ovule antipodal cell haploid egg NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason 138 Assertion (A) Pollen grain of angiosperm is ■ Direction (Q. No. 134-148) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 139 140 134 Assertion (A) Gynoecium consists of pistil. Reason (R) It represents the male reproductive part in flowering plants. 135 Assertion (A) Meiosis is the cell division which occurs in the sexually reproducing organisms. Reason (R) Meiotic cell division results into two cells having exactly same genetic makeup. 136 Assertion (A) Flowers are the structures related to sexual reproduction in flowering plants. Reason (R) Various embryological processes of plants occur in a flower. 137 Assertion (A) Megaspore mother cell undergoes meiosis to produce four megaspores. Reason (R) Megaspore mother cell and megaspore both are haploid. 141 142 143 144 considered as the male gametophyte. Reason (R) Pollen grain contains stigma, style and ovary. Assertion (A) Geitonogamy is genetically similar to autogamy. Reason (R) In geitonogamy, pollen grains come from the same plant. Assertion (A) Cleistogamous flowers produce assured seed set in the absence of pollinators. Reason (R) Cleistogamous flowers do not open at all. Assertion (A) Removal of anthers is first step in artificial hybridisation. Reason (R) It prevents contamination of anthers. Assertion (A) Endosperm development preceds embryo development. Reason (R) It assures nutrition to the developing embryo. Assertion (A) Non-albuminous seeds have no residual endosperm. Reason (R) The endosperm is completely consumed during embryo development. Assertion (A) Mango is a false fruit. Reason (R) The thalamus also contributes to fruit formation in false fruits. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 34 145 Assertion (A) Some fruits are seedless or contain non-viable seeds. Reason (R) They are produced without fertilisation. 146 Assertion (A) In apomixis, plants of new genetic variations are not produced. Reason (R) In apomixis, reductional division takes place. 147 Assertion Parthenocarpy involves the formation of seedless fruits. AIIMS 2019 Reason Apomixis occurs without fertilisation. 148 Assertion In apomixis, the plants of new genetic sequence are produced. AIIMS 2019 Reason In apomixis, two organisms of same genetic sequence meet. II. Statement Based Questions 149 Read the following statements and choose the correct ones. I. Non-essential floral organs in a flower are sepals and petals. II. Stamens represent microsporophylls. III. A dithecious anther consists of four microsporangia two in each lobe. IV. The anther wall has middle layer lieing between endothecium and tapetum. (a) I and II (c) III and IV (b) II and III (d) I, II, III and IV 150 Which one of the following statement is correct? (a) (b) (c) (d) Hard outer layer of pollen is called intine Sporogenous tissue is haploid Endothecium produces the microspores Tapetum nourishes the developing pollen NEET 2013 151 Self-incompatibility is a device for I. ensuring cross-pollination. II. preventing self-fertilisation. III. ensuring self-fertilisation. IV. genetic control for self-fertilisation. Choose the correct statements from those given above. (a) I, II and III (c) I, III and IV (b) I, II, III and IV (d) I, II and IV 152 Which of the following statement(s) is/are correct? I. The stigma serves as a landing platform for pollen grains. II. Ovarian cavity is also known as ovarian locule and is present inside the ovary. III. Placenta is located inside the ovarian cavity. IV. The ovule is attached to the placenta by funicle. (a) I, II and III (c) I and III (b) I, II and IV (d) I, II, III and IV 153 Read the following statements. I. Generative cell is bigger and contains abundant food reserve. II. Vegetative cell is small and floats in the cytoplasm of the generative cell. III. In angiosperms various stages of reductional divisions can be studied in young anthers. IV. Hilum represents the junctions between ovule and funicle. Choose the option with correct set of statements. (a) I and II (c) II and IV (b) I and III (d) III and IV 154 Read the following statements and choose the correct statements. I. Heterostyly as a contrivance for cross-pollination is found in Primula vulgaris. II. Cleistogamous flower is present in Commelina. III. Tallest flower are of Amorphophallus. IV. In monoecious condition, both male and female flowers are borne on same plant, an example of such plant is Cucurbita. (a) (b) (c) (d) I and II II and III III and IV I, II, III and IV 155 Read the following statements and choose the correct ones. I. Mature ovules in which micropyle comes to lie close to the funiculus the ovule is anatropous. II. When micropyle, chalaza and hilum lie in a straight line the ovule is said to be orthotropous. III. Megasporangium along with its protective integument is called ovule. (a) I and II (c) I and III (b) II and III (d) I, II and III 156 Consider the following statements. I. Pollination by bats is known as chiropterophily. II. Pollination by ants is known as ornithophily. (a) (b) (c) (d) Both statements I and II are true Statements I is true, but II is false Statements I is false, but II is true Both statements I and II are false 157 Which one of the following statement is incorrect about pollination? (a) Anemophily is by wind and occurs in grasses and date palm (b) Hydrophily is by water and occurs in Zostera, Vallisneria and Ceratophyllum (c) Entomophily is by insects and occurs in rose, jasmine, Salvia, etc. (d) Ornithophily is by birds and occurs in Adansonia www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 158 Which of the following statement(s) is/are correct about Parthenium (carrot grass)? (a) Parthenium came into India as a contaminant with imported wheat (b) It has became ubiquitous in occurrence (c) It causes pollen allergy (d) All of the above 159 Choose the incorrect statement from the following. (a) Long ribbon-like pollen grains are seen in some aquatic plants (b) In some insect species, the floral reward for pollination is the safe place to lay eggs in the flower (c) Insect robbers consume pollens or nectar without bringing about pollination (d) Majority of the flowering plants produce homosexual flowers 160 Refer to the given characteristics of some flowers : I. Flowers are small. They are often packed in inflorescence. II. Flowers are colourless, nectarless and odourless III. Well exposed stamens. IV. Pollen grains produced in large number, light and non-sticky. V. Flowers often have a single ovule in each ovary. VI. Stigma-large, often feathery. The above features are the characteristics of (a) (b) (c) (d) Self-pollination Anemophily (pollination by wind) Ornithophily (pollination by birds) Entomophily (pollination by insects) 161 The events in pollen-pistil interaction are given below. I. Pollen grain germinates to form pollen tube. II. Pollen tube enters the ovule through micropyle. III. Pollen grain reaches the stigma. IV. Pollen tube grows through the tissues of stigma and style and reaches the ovary. The sequential order of their occurrence is (a) III → I → IV → II (b) II → IV → III → I (c) III → IV → II → I (d) II → III → I → IV 162 Which of the following statement is correct? (a) Pollination gives the guarantee of the promotion of post-pollination events that lead to fertilisation (b) The events ‘from pollen deposition on stigma until pollen tubes enter the ovule’ are together referred to as pollen-pistil interaction (c) Pollen-pistil interaction is a dynamic process involving pollen recognition followed by only promotion (not rejection) of the pollen (d) Pistil has no ability to recognise the pollen, whether right or wrong type 35 163 Study the following and find correct statement(s). I. Pollination by water is quite rare in flowering plants and is limited to about 50 genera, mostly monocotyledons. II. Water is a regular mode of transport for the male gametes among higher plant groups. III. Distribution of bryophytes and pteridophytes are limited because of the need of water for transport of male gametes and fertilisation. (a) Only I (c) Only III (b) II and III (d) Only II 164 Read the following statements. I. Double fertilisation was discovered by Nawaschin in Lilium and Fritillaria. II. The total number of nuclei involved in double fertilisation is five. III. The central cell of embryo sac, as a result of triple fusion becomes primary endosperm cell (PEC). IV. Synergids are haploid. Choose the correct set of statements. (a) (b) (c) (d) I, II and III II and IV I, III and IV I, II, III and IV 165 Find out the correct statement(s). I. Most common endosperm is of nuclear type. II. Coconut water is male gametophyte. III. Coconut has both free-nuclear and cellular type of endosperm. (a) I, II and III (c) II and III (b) I and III (d) I and II 166 Find out the correct statement(s). I. Endosperm formation is the prior event than embryo formation. II. Angiospermic and gymnospermic endosperm are 3n and n , respectively. III. Endospermic seeds are found in castor, barley and coconut. IV. In albuminous seed, food is stored in endosperm and in non-albuminous seeds, it is strored in cotyledons. (a) I and IV (c) I and III (b) II and III (d) I, II, III and IV 167 Observe the following diagrams. Seed Achene Endocarp (A) A. Fruit of apple Mesocarp (B) B. Fruit of strawberry www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 36 Select correct statement regarding the above fruits. (a) Both are parthenocarpic fruits which develops without fertilisation (b) Both are true fruits which develops only from the ovary (c) Both are false fruits in which thalamus also contributes to fruit formation (d) A is false fruit and B is true fruit 168 The given diagram is related to castor seeds. Select the incorrect statement regarding the labelled parts. Seed coat Endosperm Shoot apical meristem Cotyledon Hypocotyl Column II A. Antipodal 1. 3n B. Central cell 2. 2n C. MMC 3. (n + n) D. Endosperm 4. n Codes A (a) 4 (c) 4 B 3 3 C 1 2 D 2 1 A 3 3 (b) (d) B 2 4 169 Match the following columns. Column I (Seeds / Fruits) A. Endospermic seed 1. Wheat B. Non-endospermic seed 2. Mango C. True fruit 3. Cashew D. False fruit 4. Pea A (b) 1 (d) 4 B 4 3 Codes A (a) 4 (c) 1 B 2 3 C 3 2 D 1 4 C 2 2 Column I (Agents of pollination) B. Inner integuments 2. Tegmen A. Wind 1. Anemophily C. Ovary 3. Fruit B. Water 2. Hydrophily D. Ovules 4. Seed C. Insects 3. Entomophily D. Birds 4. Ornithophily D 4 4 A (b) 3 (d) 4 Testa Column II (Technical term) Outer integuments C 2 3 B 4 3 170 Match the following columns. Column I (Ovary) Column II (Pistil) C 1 2 D 3 1 173 Match the following columns. Column II B 3 2 D 2 1 Codes A (a) 1 (c) 4 B 2 2 C 3 3 D 4 1 (b) (d) A 1 2 B 3 3 C 2 4 D 4 1 174 Match the following columns. Column I (Parts of seed) Column II (Features) A. Monocarpellary 1. Free pistil B. Multicarpellary 2. Fused pistil A. Cotyledon 1. Portion below the cotyledon C. Syncarpous 3. Many pistil B. Epicotyl 2. Portion above the cotyledon D. Apocarpous 4. Single pistil C. Plumule 3. Stem tip D. Hypocotyl 4. Leaf of embryo Codes A (a) 1 (b) 4 (c) 3 (d) 4 B 2 3 4 3 C 3 2 2 1 D 4 1 1 2 D 4 2 Column II (Examples) A. Codes A (a) 1 (c) 1 C 1 1 172 Match the following columns. III. Matching Type Questions 1. Column I Root tip (a) Seed coat protect the seed from physical, temperature or water damage (b) Endosperm provides nourishment to the developing embryo (c) Castor seed has single cotyledon, i.e. monocotyledonous and is albuminous (d) Hypocotyl terminates at its lower end in the root tip Column I 171 Match the following columns. Codes A (a) 1 (c) 4 B 2 2 C 3 3 D 4 1 (b) (d) A 1 1 B 3 2 C 2 4 D 4 3 www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 175 Match the following columns. Column I (Other modes of reproduction) Column II (Examples) A. Parthenocarpy 1. Grasses B. Apomixis 2. Citrus C. Polyembryony 3. Banana Codes A (a) 1 (c) 3 37 Codes A (a) 2 (b) 1 (c) 3 (d) 4 B 3 2 2 3 C 4 3 4 2 D 1 4 1 1 177 Match the following columns. Column I B 2 2 C 3 1 A (b) 2 (d) 3 B 1 1 C 3 2 176 Match the following columns. Column I Column II A. Viability of pollen grains 1. Genetically different pollen grains B. Autogamy 2. Prevailing temperature and humidity C. Pollen allergy 3. Genetically similar pollen grains D. Xenogamy 4. Carrot grass Column II A. Ovary 1. Groundnut, mustard B. Ovule 2. Guava, orange, mango C. Wall of fruit 3. Pericarp D. Fleshy fruits 4. Seed E. Dry fruits 5. Fruit Codes A (a) 5 (b) 1 (c) 1 (d) 5 B 4 2 3 4 C 3 3 2 1 D 2 4 4 2 E 1 5 5 3 NCERT & NCERT Exemplar MULTIPLE CHOICE QUESTIONS NCERT 183 Which type of pollination occurs in self-incompatible 178 What is the correct sequence of development of microsporogenesis? (a) Pollen grain → Sporogenous tissue → Microspore tetrad → PMC → Male gametes (b) Sporogenous tissue → Microspore tetrad → PMC → Male gametes (c) Pollen grain → Male gametes → PMC → Microspore tetrad – Sporogenous tissue (d) Sporogenous tissue → PMC → Microspore tetrad → Pollen grain → Male gametes 179 Strategies to prevent self-pollination are (a) dioecy (c) Both (a) and (b) (b) self-incompatibility (d) None of these 180 The portion of embryonal axis above the level of cotyledons is (a) epicotyl (b) hypocotyl (c) plumule (d) radicle 181 Perisperm is (a) residual nucellus (c) covering of fruit (b) residual endosperm (d) None of these 182 Name the part of gynoecium that determines the compatible nature of pollen grain. (a) Pistil (c) Ovum (b) Ovary (d) Ovule plant? (a) Self-pollination (c) Water pollination (b) Cross-pollination (d) Wind pollination NCERT Exemplar 184 In a typical complete, bisexual and hypogynous flower the arrangement of floral whorls on the thalamus from the outermost to the innermost is (a) calyx, corolla, androecium and gynoecium (b) calyx, corolla, gynoecium and androecium (c) gynoecium, androecium, corolla and calyx (d) androecium, gynoecium, corolla and calyx 185 Among the terms listed below, those that are not technically correct names for a floral whorl are I. androecium II. carpel III. corolla IV. sepal (a) I and IV (c) II and IV (b) III and IV (d) I and II 186 Embryo sac is to ovule as ...... is to an anther. (a) stamen (b) filament (c) pollen grain (d) androecium www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 38 187 A dicotyledonous plant bears flowers, but never produces fruits and seeds. The most probable cause for the above situation is (a) plant is dioecious and bears only pistillate flowers (b) plant is dioecious and bears both pistillate and staminate flowers (c) plant is monoecious (d) plant is dioecious and bears only staminate flowers 188 During microsporogenesis, meiosis occurs in (a) endothecium (b) microspore mother cells (c) microspore tetrads (d) pollen grains 195 In an embryo sac, the cells that degenerate after fertilisation are (a) synergids and primary endosperm cell (b) synergids and antipodals (c) antipodals and primary endosperm cell (d) egg and antipodals 196 While planning for an artificial hybridisation programme involving dioecious plants, which of the following steps would not be relevant? (a) Bagging of female flower (b) Dusting of pollen on stigma (c) Emasculation (d) Collection of pollen 189 From among the sets of terms given below, identify 197 In the embryos of a typical dicot and a grass, true those that are associated with the gynoecium. homologous structures are (a) Stigma, ovule, embryo sac, placenta (b) Thalamus, pistil, style, ovule (c) Ovule, ovary, embryo sac, tapetum (d) Ovule, stamen, ovary, embryo sac (a) coleorhiza and coleoptile (b) coleoptile and scutellum (c) cotyledons and scutellum (d) hypocotyl and radicle 190 Starting from the innermost part, the correct sequence of parts in an ovule are (a) egg, nucellus, embryo sac, integument (b) egg, embryo sac, nucellus, integument (c) embryo sac, nucellus, integument, egg (d) egg, integument, embryo sac, nucellus 191 From the statements given below choose the option that are true for a typical female gametophyte. I. It is 8-nucleate and 7-celled at maturity. II. It is free-nuclear during the development. III. It is situated inside the integument, but outside the nucellus. IV. It has an egg apparatus situated at the chalazal end. (a) I and IV (c) I and II (b) II and III (d) II and IV 192 Autogamy can occur in a chasmogamous flower if (a) pollen matures before maturity of ovule (b) ovules mature before maturity of pollen (c) Both pollen and ovules mature simultaneously (d) Both anther and stigma are of equal lengths 193 Choose the correct statement from the following. (a) Cleistogamous flowers always exhibit autogamy (b) Chasmogamous flowers always exhibit geitonogamy (c) Cleistogamous flowers exhibit both autogamy and geitonogamy (d) Chasmogamous flowers never exhibit autogamy 194 From among the situations given below, choose the one that prevents both autogamy and geitonogamy. (a) Monoecious plant bearing unisexual flowers (b) Dioecious plant bearing only male or female flowers (c) Monoecious plant with bisexual flowers (d) Dioecious plant with bisexual flowers 198 The phenomenon observed in some plants where in parts of the sexual apparatus is used for forming embryos without fertilisation is called (a) parthenocarpy (b) apomixis (c) vegetative propagation (d) sexual reproduction 199 In a flower, if the megaspore mother cell forms megaspores without undergoing meiosis and if one of the megaspores develops into an embryo sac, its nuclei would be (a) haploid (b) diploid (c) a few haploid and a few diploid (d) with varying ploidy 200 The phenomenon wherein, the ovary develops into a fruit without fertilisation is called (a) parthenocarpy (c) asexual reproduction (b) apomixis (d) sexual reproduction 201 In a fertilised embryo sac, the haploid, diploid and triploid structures are (a) synergid, zygote and primary endosperm nucleus (b) synergid, antipodal and polar nuclei (c) antipodal, synergid and primary endosperm nucleus (d) synergid, polar nuclei and zygote 202 The outermost and innermost wall layers of microsporangium in an anther are respectively. (a) Endothecium and tapetum (b) Epidermis and endodermis (c) Epidermis and middle layer (d) Epidermis and tapetum 203 A particular species of plant produces light, non-sticky pollen in large numbers and its stigmas are long and feathery. These modifications facilitate pollination by (a) insects (b) water (c) wind (d) animals www.mediit.in 39 CHAPTER 02 > Sexual Reproduction in Flowering Plants Answers Mastering NCERT with MCQs 1 (c) 2 (a) 3 (d) 4 (c) 5 (b) 6 (d) 7 (d) 8 (d) 9 (a) 10 (a) 11 (d) 12 (d) 13 (c) 14 (d) 15 (b) 16 (b) 17 (b) 18 (c) 19 (a) 20 (a) 21 (c) 22 (d) 23 (d) 24 (c) 25 (c) 26 (d) 27 (b) 28 (a) 29 (a) 30 (c) 31 (a) 32 (b) 33 (b) 34 (d) 35 (c) 36 (a) 37 (a) 38 (c) 39 (a) 40 (a) 41 (c) 42 (c) 43 (a) 44 (c) 45 (c) 46 (c) 47 (b) 48 (c) 49 (b) 50 (c) 51 (d) 52 (c) 53 (d) 54 (c) 55 (d) 56 (a) 57 (c) 58 (c) 59 (c) 60 (c) 61 (a) 62 (a) 63 (b) 64 (c) 65 (a) 66 (c) 67 (a) 68 (a) 69 (b) 70 (b) 71 (d) 72 (b) 73 (c) 74 (b) 75 (b) 85 (b) 86 (c) 87 (c) 88 (d) 89 (a) 90 (b) 76 (d) 77 (a) 78 (b) 79 (b) 80 (b) 81 (b) 82 (a) 83 (d) 84 (b) 91 (a) 92 (b) 93 (d) 94 (d) 95 (c) 96 (c) 97 (c) 98 (b) 99 (b) 100 (b) 101 (b) 102 (c) 103 (d) 104 (a) 105 (d) 106 (d) 107 (c) 108 (c) 109 (c) 110 (b) 111 (a) 112 (c) 113 (d) 114 (c) 115 (a) 116 (b) 117 (d) 118 (c) 119 (a) 120 (a) 121 (a) 122 (c) 123 (d) 124 (d) 125 (a) 126 (a) 127 (c) 128 (d) 129 (d) 130 (a) 131 (c) 132 (d) 133 (b) NEET Special Types Questions 134 (c) 135 (c) 136 (a) 137 (c) 138 (c) 139 (a) 140 (a) 141 (c) 142 (a) 143 (a) 144 (d) 145 (a) 146 (c) 147 (b) 148 (d) 149 (d) 150 (d) 151 (d) 152 (d) 153 (d) 154 (d) 155 (d) 156 (b) 157 (d) 158 (d) 159 (d) 160 (b) 161 (a) 162 (b) 163 (c) 164 (d) 165 (b) 166 (d) 167 (c) 168 (c) 169 (c) 170 (b) 171 (c) 172 (b) 173 (a) 174 (c) 175 (d) 176 (a) 177 (a) NCERT & NCERT Exemplar Questions 178 (d) 179 (c) 180 (a) 181 (a) 182 (a) 183 (b) 184 (a) 185 (c) 186 (c) 187 (d) 188 (b) 189 (a) 190 (b) 191 (c) 192 (c) 193 (a) 194 (b) 195 (b) 196 (c) 197 (c) 198 (b) 199 (b) 200 (a) 201 (a) 202 (d) 203 (c) Answers & Explanations 4 5 6 7 10 12 Stamen represents the male reproductive part of a flower, whereas stigma, style and ovary, are the parts of a carpel or pistil which represents the female reproductive part of a flower. (c) The terminal structure of stamen is called anther, which contains pollen grains (male gametophyte). Pollen grains are haploid in nature. (b) The dehiscence (release of pollen grain) of anther occurs through the line of dehiscence which is the running groove on anther longitudinally. It separates the theca of anther. (d) A typical angiosperm anther is bilobed with each lobe having two theca. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corner with two in each theca. (d) Microsporangium develops further and becomes pollen sac. It is like a sac in which pollen develops. It is called pollen sac at the time of maturity. (a) Sporogenous tissue occupies the centre of each microsporangium. Each cell of this tissue is a potential pollen mother cell and can give rise to microspore tetrad. (d) Microsporangium is surrounded by four wall layers. The outermost layer is epidermis which is followed by endothecium, the middle layer and the innermost layer called tapetum. The three outer layers of microsporangium perform the function of protection and help in dehiscence of anther to release pollen. 13 (c) Microspore mother cell and pollen mother cell are 16 18 21 23 24 26 the same terms and form male gametes (pollens) by the process called microsporogenesis. (b) As the anthers of angiospermic mesophytic plants mature and dehydrate, the line of dehiscence ruptures releasing the microspores in atmosphere. These microspores dissociate from each other and develop into pollen grains. (c) The inner layer of pollen grain is called intine. It is a continuous and thin layer made up of cellulose and pectin. (c) Sporopollenin is the hardest substance in plant kingdom. It is the major constituent of outer layer, exine of pollen grains and is non-degradable. (d) Sporopollenin enables in preservation of pollen as fossils. Since, sporopollenin cannot be degraded by any enzyme. It is not affected by high temperature, strong acid or strong alkali. Thus, it keeps pollen grains well-preserved as fossils. (c) The germ pores are apertures in the exine layer of a pollen grain which help in the initiation of pollen tube and the release of the male gametes during fertilisation. There are usually three germ pores in dicots (tricolpate) and one in monocots (monocolpate). (d) When a pollen grain is mature it contains two cells, a vegetative cell and generative cell. The vegetative cell is bigger, has abundant food reserve and a large irregularly shaped nucleus. The generative cell is small Answers & Explanations 2 (a) Stamen is the odd one out among the other options. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 40 27 28 30 31 32 33 34 37 38 39 Answers & Explanations 40 41 43 44 45 and floats in the cytoplasm of the vegetative cell. It is spindle-shaped with dense cytoplasm and a nucleus. (b) The generative cell of a pollen grain divides to form two male gametes in order to achieve the 3-celled stage in angiospermic plants. (a) 60% of angiosperms shed their pollens at 2-celled stage and in rest 40%, the pollens are shed at 3-celled stage. (c) Pollen grains are rich in nutrients. These are available in the market in the form of tablets and are used as food supplements to improve health. Pollen consumption has been claimed to enhance the performance of athletes and race horses. (a) Pollen grains can be stored for several years in liquid nitrogen having a temperature of −196°C (cryopreservation). Pollen grains can be later used in plant breeding programmes. (b) The part labelled as C shows ovary. It is the site of fertilisation, the process in which the fusion of male and female gametes takes place. Fertilisation occurs in the ovary of a pistil. (b) The diagram represents the multicarpellary, syncarpous pistil of Papaver. The gynoecium of this plant consists of more than one pistil, showing multicarpellary condition. These pistils are fused together and hence are called syncarpous. (d) The diagram shows the multicarpellary apocarpous pistil of Michelia. The gynoecium of this ovary consists of more than one pistil (multicarpellary) which are free (apocarpous). (a) Ovule of an angiosperm is equivalent to the megasporangium which consists of 2 synergids, 1 egg, 3 antipodal cells and a secondary nucleus. (c) An ovule is an integumented megasporangium found in angiosperms, which develops into seeds after fertilisation. (a) Chalazal pole is present just opposite to the micropylar end and represents the basal part of the ovule. (a) Integuments enclose a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials. (c) Embryo sac is also called the female gametophyte. In flowering plants, it is formed by the division of the haploid megaspore nucleus and acts as the site of fertilisation and development of the embryo. (a) Megaspore Mother Cell (MMC) is found in the micropylar region of the nucellus. It is a large cell containing dense cytoplasm and prominent nucleus. (c) In most of the angiosperms, the megaspore mother cell ( 2n ) divides meiotically (reductional division) to produce 4 cells. Out of these, three degenerate and the remaining one forms the functional megaspore. This further divides mitotically and forms embryo sac. (c) Microsporogenesis and megasporogenesis are the processes involving the formation of male gamete and 46 47 52 55 56 57 63 female gamete, respectively by meiotic cell division in flowering plants. (c) In angiosperms, functional megaspore develops into an embryo sac. The functional megaspore is the first cell of the female gametophyte. (b) The most common type of female gametophyte (embryo sac) in angiosperms is the monosporic embryo sac in which the embryo sac develops from a single functional megaspore (n), while the other three megasproes degenerate. The functional megaspore undergoes three sequential mitotic divisions and gives rise to the 8-nucleate and 7-celled mature embryo sac. (c) The functional megaspore develops into the embryo sac containing 2 synergids, l egg cell, 1 central cell and 3 antipodal cells. Thus, option (c) gives the correct number of different cells in an embryo sac. (d) The function of filiform apparatus is to guide the entry of pollen tube into the synergids and release of sperm cells. (a) A typical angiospermic embryo sac at maturity has 8-nuclei. Six out of the eight nuclei are surrounded by cell walls and organised into cells (egg apparatus and antipodal cells) and the remaining two nuclei, called polar nuclei, are situated below the egg apparatus in the large central cell. (c) Female gametophyte is 7-celled structure. Out of these, three cells are grouped together at the micropylar end and constitute of two synergids and one egg cell, three antipodal cells are at the chalazal end and the large central cell. (b) Cleistogamous flowers are strictly autogamous because they always remain close for ensuring self-pollination. In these flowers, there is no chance of cross-pollination. 66 (c) Cleistogamous flowers are not dependent on pollinators. These are bisexual flowers which never open, i.e. always remain closed. In such flowers, the anthers and stigma lie very close to each other. When anthers dehisce in the flower buds, pollen grains come in contact with the stigma of the same flower, i.e. autogamy occurs. So, these flowers produce assured seed set, even in the absence of pollinators. 67 (a) Commelina has flowers which does not open at all, i.e. cleistogamous flowers. So, even in the absence of pollinating agent, assured seed setting takes place in Commelina. 68 (a) Geitonogamy is a type of self-pollination. In other words, geitonogamy is the transfer of pollen grains from the anther of one flower to the stigma of another flower of either the same or a genetically similar plant. 69 (b) Xenogamy is also called cross-pollination. In this, transfer of pollen grains takes place between the anther and the stigma of different plants of same species. 71 (d) Wind pollinated pollens are non-sticky and light so that they can go far away in wind currents. These are produced in large numbers, because there is a lot of wastage of pollens. www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants condition, flowers occur on different plants, i.e. male and female flowers are present on different plants. Hence, it does not favour autogamy and geitonogamy because autogamy takes place in bisexual flowers and geitonogamy takes place between different flowers of the same plant. 72 (b) Maize (corn cob) stigma are feathery and long, 75 76 78 79 80 81 82 83 84 85 (b) Autogamy and geitonogamy both are prevented in the papaya plant. This is because in papaya, male and female flowers are present on different plants that is each plant is either male or female (dioecy). 91 (a) The process of removal of anther from flower bud before it dehisces is called as emasculation. When an emasculated flower is covered with a bag of suitable size to prevent contamination of its stigma with unwanted pollen it is called bagging. These methods are a part of artificial hybridisation technique used in plants. 93 (d) Double fertilisation is the fusion of two male gametes to two different cells of the same female gametophyte. It consists of the following two events l l Syngamy is the fusion of the egg nucleus with one male gamete. Triple fusion is the fusion of second male gamete and polar nuclei of central cell. 95 (c) Out of the given structures, antipodal cell, egg cell, 96 100 102 103 104 105 synergid cell and male gamete are haploid. Thus, option (c) is correct. The ploidy of the remaining structures mentioned is diploid. (c) Out of the male gametes discharged in the synergid, one fuses with the egg and other fuses with central cell nuclei. The fusion between male gamete and egg is called syngamy or true fertilisation which forms zygote (2n). The fusion between male gamete and central cell nuclei is called triple fusion and it results in the formation of a triploid primary endosperm nucleus (3n). (b) Two polar nuclei and one nuclei of the remaining male gamete (total 3 nuclei) are involved in the triple fusion of double fertilisation. (c) Option (c) is correct. If stem has 2n = 10 number of chromosomes, then Endosperm = 3n = 5 × 3 = 15 chromosomes. Egg cell = 1n = 1 × 5 = 5 chromosomes. Polar nuclei = 2n = 2 × 5 = 10 chromosomes. (d) Option (d) is correct. The ploidy of endosperm is 3n. Now, Chromosome given = 36 36 Haploid number = = 12 3 Chromosomes of male and female gametes are haploid, so answer is 12 and 12, respectively. (a) After triple fusion, i.e. the fusion of male gametes and polar nuclei, the central cell of female gametophyte becomes the Primary Endosperm Cell (PEC). (d) Option (d) is correct. If a male plant is diploid ( 2n ) it will produce haploid male gamete (n ). Answers & Explanations 73 which wave in the air to trap pollen grains. (c) The flowers with packed inflorescence and single ovary are wind pollinated. These flowers produce pollen grains in large numbers and such pollen grains are light weighted sometimes winged, e.g. cereals and grasses. (b) Insect or Wind act as pollinating agents in the majority of aquatic plants such as water hyacinth and water lily. In these plants, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. (d) Vallisneria is a water pollinated plant. In Vallisneria, the female flowers reach the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. These are carried passively by water currents to the female flowers at the surface of water. (b) Wind pollinated and water pollinated flowers are non-colourful. As these do not need any biotic agency for pollination, there is no need for fragrance, nectar and colourfulness. (b) Pollenkitt is present in entomophily. It is a yellow, sticky, viscous and oily layer that covers exine of some insect pollinated pollen grains. Its major function is to make the pollen to stick to the bugs. Thus, it helps in pollination. (b) Attractants and rewards are required for entomophily (insect pollination). Flowers are colourful and produce a specific odour to attract the insects for effective pollination. To sustain animal visits, flowers also provide nectar and pollen grains as rewards to them. (b) Out of the given options, only Yucca gloriosa has developed an obligate symbiotic relationship with the moth, Pronuba yuccasella. The moth cannot complete its life cycle without the association with Yucca flowers. The moth deposits its eggs in the locule of the ovary and the flower in turn gets pollinated by the moth. The larvae of the moth come out of the eggs as the seeds start developing. (a) Continued self-pollination results in inbreeding depression. Due to the continuous breeding of related species the productivity of the progeny species is reduced which leads to inbreeding depression. (d) Both option (a) and (b) are correct as Flowering plants have developed many devices to discourage self-pollination. In some species, pollen release and stigma receptivity is non-synchronised, i.e. either the pollen is released before the stigma becomes receptive or stigma becomes receptive much before the release of pollen. In other species, the anther and stigma are placed at different positions, so that the pollen cannot come in contact with the stigma of the same flower. Both these devices prevent autogamy (self-pollination) and increases cross-pollination. (b) Dioecious flowering plants prevent the occurrence both autogamy and geitonogamy in them. In dioecious 41 www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 42 106 108 111 118 120 121 Answers & Explanations 124 125 127 129 If a female plant is tetraploid ( 4n ) it will produce tetraploid polar nuclei ( 4n ). Endosperm is formed by fusion of male gamete with polar nuclei, i.e. fusion of tetraploid polar nuclei and haploid male gamete will give pentaploid (5n ) endosperm. (d) Pollen tube liberates both male gametes in synergids, out of which one male gamete fuses with egg cell and other with the polar nuclei. (c) Endospermogenesis and embryogenesis are the post-fertilisation event under which formation of endosperm and embryo take place. Whereas, megasporogenesis is the formation of megaspores and is a pre-fertilisation event. (a) Endosperm is consumed by the developing embryo in seeds of pea plant. Endosperm may either be completely consumed by the developing embryo in plants like pea, groundnut, beans before seed maturation or it may persist in mature seed in plants like castor, maize and coconut and be used up during seed germination. (c) In wheat or maize (family–Poaceae), the scutellum is thought to be a large, shield-shaped cotyledon or seed leaf, which is situated towards one side (lateral) of the embryonal axis. (a) Persistent nucellus in the seed is known as perisperm. The albuminous seeds usually retain a part of endosperm as it is not completely used up during embryo development. But in some seeds, remnants of nucellus are also persistent. This residual persistens nucellus is called perisperm, e.g. in black pepper and beet root. (a) Dehydration and dormancy are most crucial for seed storage. In dehydration, there is less amount of water due to which the seed enzymes cannot work and hence, there will be no germination. Dormancy is the time period in which seed cannot grow due to inactive state of embryo or lacking of other necessary condition for growing. (d) Thalamus contributes to fruit formation in apple, strawberry and cashewnut. In such plant species where the thalamus contributes to fruit formation, the fruits are called false fruits. But in most of the plants, the fruit develops from the ovary (true fruits) and other floral part degenerates and fall off. (a) The oldest viable seed is that of a lupine, Lupinus arcticus excavated from Arctic Tundra. The seed germinated and flowered after an estimated record of 10,000 years of dormancy. (c) Apomixis is a special mechanism found in flowering plants to produce seeds without meiosis and fertilisation. It is a type of asexual reproduction which mimics sexual reproduction and is commonly found in species of Asteraceae and grasses. (d) In varieties of both Citrus and mango ovules contain many embryos. In these varieties some of the nucellar cell surrounding the embryo sac starts dividing, protrude into the embryo sac and develop into many embryos. 130 (a) Occurrence of more than one embryo is called 131 132 133 134 135 136 137 138 139 140 polyembryony. It is generally observed in Citrus varieties. Orange and lemon are common examples of polyembryony. (c) Option (c) is correct as In asexual/vegetative and apomictic reproduction, mitotic cell divison takes place, due to which the resultant progeny are identical to the parents and to each other (clone nature of offspring). (d) Nucellar polyembryony is a form of seed production that occurs in Citrus varieties. During the development of seeds in plants that possess this genetic trait, the nucellar tissue which surrounds the megagmetophyte can produce additional embryos (polyembryony) which are genetically identical to the parent plant. These nucellar seedling are clones of the parent. (b) Synergids, antipodal cell, haploid egg do not take part in seed or apomictic seed formation because they are haploid and can only take part in sexual reproduction. Only maternal sporophytic tissue in ovule takes part in seed formation in apomictic embryogenesis as it is diploid. (c) Assertion is true, but Reason is false and can be corrected as The gynoecium represents the female reproductive part of the flower and consists of pistil. (c) Assertion is true, but Reason is false and can be corrected as In meiosis, the resultant cells do not have exactly same genetic makeup due to the process of crossing over. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The structures related to sexual reproduction in flowering plants are flowers. This is because embryological processes during sexual reproduction occur in ovary, which is a part of a flower. (c) Assertion is true, but Reason is false and can be corrected as Megaspore mother cell is diploid and megaspore is haploid. (c) Assertion is true, but Reason is false and can be corrected as Pollen grain does not contain the stigma, style and ovary. These are parts of the female reproductive structure of flower, gynoecium. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Geitonogamy is functionally cross-pollination involving a pollinating agent, but genetically it is similar to autogamy. This is because the pollen grains come from different flowers of the same plant. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Cleistogamous flowers do not open at all. This ensures fertilisation and consequently leads to the production of assured of seed-set even in the absence of pollinators. www.mediit.in CHAPTER 02 > Sexual Reproduction in Flowering Plants 142 143 144 145 146 147 148 150 corrected as Removal of anthers (emasculation) is done in artificial hybridisation as it prevents contamination of the pistil (female reproductive structure). (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Endosperm is source of nutrition for the developing embryo, thus the development of endosperm takes place before the process of embryogenesis. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. In non-albuminous seeds, the endosperm is fully consumed by the developing embryo and thus, no residue is left in such seeds. (d) Assertion is false, but Reason is true. Assertion can be corrected as Mango is a true fruit, which develops only from the ovary. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Parthenocarpic fruits are either seedless or contain non-viable seeds. This is because such fruits are formed without fertilisation. (c) Assertion is true, but Reason is false and can be corrected as Apomixis is the type of asexual reproduction in which seeds are produced without meiosis (reductional division) and syngamy. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The correct explanation is as follows Parthenocarpy involves the formation of seedless fruits, because the fruit formation from parthenocarpy does not involve pollination and fertilisation and hence, fruits develop without seed formation. Apomixis is a mechanism that mimics sexual reproduction and produces seeds without the union of male and female gametes. The diploid egg cell is formed without meiotic division and develops into embryo without fertilisation, e.g. members of Asteraceae and grasses. (d) Assertion is false, but Reason is true. Assertion can be corrected as In apomixis, sexual reproduction is completely replaced by asexual reproduction. In this process, no new genetic sequence is formed as the progeny is genetically identical to the parent. (d) The statement in option (d) is correct. Rest of the statements are incorrect and can be corrected as l l l The inner wall of pollen grain is called intine. Sporogenous tissue is diploid and undergoes meiotic division to form microspore tetrads. Endothecium is the wall around the microsporangium, which provides protection and helps in the dehiscence of anther to release the pollen. 151 (d) Statements I, II and IV are correct. Statement III is incorrect and can be corrected as Self-incompatibility is a device which ensures cross-pollination, prevents self-fertilisation and keeps genetic control for self-fertilisation. 153 (d) Statements III and IV are correct. Statements I and II are incorrect and can be corrected as l l In a mature pollen grain vegetative cell is bigger and has abundant food reserve and a large irregular shaped nucleus. The generative cell is small and floats in the cytoplasm of vegetative cell. It is spindle-shaped with dense cytoplasm and nucleus. 156 (b) Statement I is true, but statement II is false. The false statement can be corrected as Pollination by ants is called myrmecophily. 157 (d) The statement in option (d) is incorrect and can be corrected as l l Ornithophily is pollination by birds and occurs in Butea, Bignonia, etc. In Adansonia, chiropterophily occurs (i.e. pollination by bats). Rest of the statements are correct. 159 (d) The statement in option (d) is incorrect and can be corrected as Majority of the flowering plants produce bisexual flowers. Rest of the statements are correct. 162 (b) The statement in option (b) is correct. Rest of the statements are incorrect and can be corrected as l l l Pollination does not give the guarantee of the promotion of post-pollination events that lead to fertilisation. Pollen-pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen. The pistil has the ability to recognise the pollen, whether it is of the right type (compatible) or of the wrong type (in compatible). 163 (c) Statement III is correct. Statements I and II are incorrect and can be corrected as l l Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons. Water is a regular mode of transport for the male gametes among lower plant groups such as algae and bryophytes. 165 (b) Statements I and III are correct, but statement II is incorrect and can be corrected as The coconut water from tender coconut represents free-nuclear endosperm not male gametophyte and the surrounding white kernel is the cellular endosperm. 167 (c) The statement in option (c) is correct. Rest of the statements are incorrect and can be corrected as Answers & Explanations 141 (c) Assertion is true, but Reason is false and it can be 43 www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 44 168 178 179 180 181 182 Answers & Explanations 184 185 186 187 The fruit of apple (A) and fruit of strawberry (B), are false fruits, in which thalamus also contributes to fruit formation alongside ovary. These fruits are not parthenocarpic because parthenocarpic fruits are seedless and are formed without fertilisation. (c) The statement in option (c) is incorrect and can be corrected as Castor seed is dicotyledonous, i.e. with two cotyledons and is albuminous, i.e. having residual endosperm. Rest of the statements are correct. (d) The correct sequence is given in option (d). During microsporogenesis, the sporogenous tissue initially forms Pollen Mother Cell (PMC). Then this pollen mother cell undergoes meiotic division to form microspore tetrad. The microspores further develop into pollen grains, which contain the male gametes. (c) Dioecy and self-incompatibility are the methods to prevent self-pollination in plants. In dioecy, male and female flowers are borne on separate plants. So, that cross-pollination is promoted. In self- incompatibility, pollens are prevented to fertilise the ovules of same flower by inhibiting pollen germination on the pistil. (a) A typical dicotyledonous embryo consists of an embryonal axis and two cotyledons. The portion of embryonal axis above the level of cotyledon is the epicotyl and below the level of cotyledon is hypocotyl. (a) In some plants/seeds, such as black pepper remains of nucellus are also persistent, this is called as perisperm. (a) The pistil is the part of gynoecium which has the ability to recognise the pollen. Thus, determine the compatible nature of pollen grain. (a) In a typical complete, bisexual and hypogynous flower, the arrangement of floral whorls on the thalamus from the outermost to the innermost is Calyx is the whorl of sepals is the outermost. Corolla is the whorl of petals inside the calyx. Androecium is the whorl of stamens inside the corolla. Gynoecium is the whorl of pistils in the centre of the flower forming the innermost whorl. (c) Sepal and carpel are technically incorrect names for a whorl. This is because sepals collectively form a whorl called as calyx, while the carpel is technically known as gynoecium. (c) The pollen grains represent the male gametophyte. As the anther matures and dehydrates, the microspore dissociates from each other and develop into pollen grains. So, embryo sac is to ovule as pollen grains is to an anther. (d) In dioecious plants, the unisexual flower is either staminate, i.e. bearing stamens only or is pistillate bearing only pistil or carpel. For the production of fruits and seeds fertilisation must take place, which is possible only in the presence of both male and female flowers. So, in this situation plant is dioecious and bears only staminate flowers. 188 (b) During microsporogenesis, meiosis occurs in Microspore Mother Cell (MMC) and four haploid microspores (microspore tetrad) are formed. 189 (a) Gynoecium is the female reproductive part of a flower and is also called pistil. Each pistil has three parts, i.e. stigma, style and ovary. Inside the ovarian cavity, the placenta is located. Arising from placenta is the ovule. The functional megaspore undergoing the meiotic division develops into embryo sac. Thus, option (a) is correct. 190 (b) Starting from the inner to the outer side of ovule, the ovule bears egg cell, embryo sac, nucellus, and integument. 191 (c) Statements I and II are correct. Statements III and IV are incorrect and can be corrected as l l Female gametophyte is present inside the nucellus. Egg apparatus is situated at the micropylar end. 192 (c) Autogamy is self-pollination. In chasmogamous 193 194 195 196 197 199 202 203 flower, anthers and stigma are exposed. For autogamy in such a flower to take place, pollen and ovule should mature simultaneously and anther and stigma should lie close to each other. (a) The statement in option (a) is correct as Cleistogamous flowers (that do not open at all) always exhibit autogamy. Rest of the statements are incorrect and can be corrected as Chasmogamous flowers (with exposed anther and stigma) can exhibit autogamy, geitonogamy or xenogamy. (b) Dioecious plants (bearing only male or female flowers) prevent both autogamy and geitonogamy. (b) In a fertilised embryo sac, antipodals and synergids gradually degenerate after the formation of zygote. (c) If the female parent produces unisexual (dioecious) flowers, there is no need for emasculation. Because in a dioecious flower only single reproductive structure is present thus chances of self-pollination are not there. (c) In the embryos of a typical dicot and a grass (monocot), true homologous structures are cotyledons and scutellum. This is because in the monocots such as the grass family a single cotyledon is present which is called scutellum. (b) Option (b) is correct. Megaspore mother cell is diploid (2n). lf it forms megaspores without meiosis, the megaspores will be diploid (2n) too. If this diploid megaspore develops into embryo sac, its nuclei would also be diploid. (d) A typical microsporangium is generally surrounded by four-wall layers, i.e. the epidermis (outermost protective layer), then endothecium, then middle fibrous layers and the tapetum (innermost nutritive layer). (c) Wind pollination requires light and non-sticky pollen grains so that, they can be transported with wind currents and its stigma are long and feathery to easily trap airborne pollen grains. www.mediit.in CHAPTER > 03 Human Reproduction NEET Å KEY NOTES Humans are sexually reproducing and viviparous (i.e. give birth to young ones) organisms, having distinct male and female sexes. Å The testes are situated outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining the low temperature of the testes (2-2.5°C lower than the normal internal body temperature) necessary for the production of sperms (spermatogenesis). Male Reproductive System Å The male reproductive system is located in the pelvis region. Å Å It includes a pair of testes, accessory ducts, glands and the external genitalia (penis). In adults, each testis is oval in shape, with a length of about 4-5 cm and width of about 2-3 cm. Å Each testis has about 250 compartments called testicular lobules and each lobule contains one to three highly coiled seminiferous tubules. Å Seminiferous tubules are lined inside by two types of cells, i.e. male germ cells (spermatogonia), undergo meiotic divisions leading to sperm formation and Sertoli cells, provide nutrition to the dividing germ cells. Region outside the seminiferous tubules has Leydig cells or interstitial cells, which secrete testicular hormones called androgens. Å The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. These ducts store and transport the sperms from the testis to the outside through urethra. The urethra originates from urinary bladder and extends through the penis to its external opening, i.e. urethral meatus. Ureter Seminal vesicle Urinary bladder Vas deferens Prostate gland Penis Urethra Glans penis Foreskin Ejaculatory duct Rectum Anus Bulbourethral gland Testis Scrotum Diagrammatic sectional view of male pelvis showing reproductive system www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 46 Å The penis is the highly vascularised external copulatory organ in males. The enlarged end of penis called the glans penis, covered by a loose fold of skin called foreskin. Ureter Å Å Urinary bladder Vas deferens Seminal vesicle Prostate gland Bulbourethral gland The oviducts (Fallopian tube), uterus and vagina constitute the female accessory ducts. Each Fallopian tube is about 10-12 cm long and extends from the periphery of each ovary to the uterus, the part closer to the ovary is the funnel-shaped infundibulum. The edges of the infundibulum possess finger-like projections called fimbriae, which help in collection of the ovum after ovulation. The infundibulum leads to a wider part of the oviduct called ampulla. The last part of the oviduct, isthmus has a narrow lumen and it joins the uterus. Uterine fundus Epididymis Uterine cavity Urethra Vasa efferentia Rete testis Testicular lobules Isthmus Fallopian Ampulla tube Infundibulum Testis Glans penis Foreskin Diagrammatic view of male reproductive system (part of testis is open to show inner details) Å The male accessory glands include paired seminal vesicles, a prostate and paired bulbourethral glands. Secretions of these glands constitute the seminal plasma which is rich in fructose, calcium and certain enzymes. This secretion along with the sperm forms semen. Female Reproductive System Å It includes a pair of ovaries, pair of Fallopian tubes (oviducts), uterus, cervix, vagina and external genitalia and a pair of mammary glands. Endometrium Myometrium Perimetrium Ovary Fimbriae Cervix Cervical canal Vagina Diagrammatic sectional view of the female reproductive system Å Uterus (womb) opens into vagina through a narrow cervix. The cavity of the cervix is called cervical canal which forms the birth canal along with the vagina. Å The uterus has three layers of tissue, i.e. the external thin membranous perimetrium, middle thick layer of smooth muscle, myometrium and inner glandular layer called endometrium. The female external genitalia include Mons pubis A cushion of fatty tissue covered by skin and pubic hair. Labia majora Fat padded skin folds, extend from mons pubis and surround the vaginal opening. Labia minora A pair of inner folds of tissue under labia majora. Hymen The membrane that partially covers the vaginal opening. Clitoris A tiny finger-like structure, lying at the upper junction of two labia minora above the urethral opening, is sensitive to stimulation. In females, the mammary glands are one of the secondary sexual characteristics. These are paired structures that contain glandular tissue and variable amount of fat. Glandular tissue is divided into 15-20 mammary lobes, having clusters of cells called alveoli. The mammary alveolus secretes milk and stores in its lumen. These alveoli open into mammary tubules, which join to form mammary duct. The numerous mammary ducts connect to form wider ampulla which connects to lactiferous duct from which milk is sucked out. Å n Cervix Uterus Urinary bladder Pubic symphysis Urethra Clitoris Labium minora Labium majora n Rectum n Vagina n Anus n Vaginal orifice Diagrammatic sectional view of female pelvis showing reproductive system Å Å Ovaries are the primary female sex organ that produce ova and ovarian hormones. The ovaries are located one on each side of the lower abdomen. Each ovary is about 2-4 cm in length and is connected to the pelvic wall and uterus by ligaments. Each ovary is covered by a thin epithelium which encloses the ovarian stroma. The stroma is divided into two zones, i.e. a peripheral cortex and an inner medulla. NEET Å Å Å KEY NOTES www.mediit.in 47 CHAPTER 03 > Human Reproduction Gametogenesis Å It is the process by which the primary sex organs, the testis in the males and the ovaries in the females produce gametes, i.e. sperms and ovum. Å The increased level of GnRH acts at the anterior pituitary and stimulates Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH). Å LH acts on the Leydig cells and stimulates synthesis and secretion of androgens, which in turn stimulate the process of spermatogenesis. Å FSH acts on the Sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis. Å A normal human sperm structure is composed of a head, neck, a middle piece and a tail. Å Head contains anterior small acrosome, which is filled with enzymes and help in the fertilisation of the ovum. Å Middle piece possesses numerous mitochondria, which produce energy for the movement of tail that facilitates sperm motility essential for fertilisation. Spermatogenesis Å It is a process of formation of sperm through meiotic division and later some structural modifications from germ cells present in testes in males. n n n n n n The germ cells called spermatogonia are present on the inside wall of the seminiferous tubules. These cells are diploid and increase in number through mitosis. Some of the spermatogonia, primary spermatocytes, undergo meiosis, forming two equal cells called secondary spermatocytes. They are haploid (with 23 chromosomes but are still duplicate). Each of the two secondary spermatocytes undergoes second cell division (to separate the duplicate chromosomes) producing four haploid spermatids. Each has only one set of 23 (unpaired, unduplicated) chromosomes. Oogenesis Å It is the process of formation of female gametes (oocyte) through meiotic division of germ cells, present in the ovary in females. n Spermatids transform into spermatozoa (sperm cells) by developing a head, neck, middle piece and a tail. This process is called spermiogenesis. n Sperm heads become embedded in the Sertoli cells that provide nourishment and molecular signals. n n Final release of sperms (spermiation) from seminiferous tubules is under the influence of hormonal and physiological signals. n Å Spermatogenesis includes three phases as indicated in the following figure Spermatogonia Mitosis and differentiation At puberty Chromosomes number per cell (46) n n Primary spermatocytes 1st meiotic division Secondary spermatocytes n (23) 2nd meiotic division (23) n Spermatids Differentiation Spermatozoa n Diagrammatic view of phases in spermatogenesis Å It starts at the age of puberty due to significant increase in the secretion of Gonadotropin Releasing Hormone (GnRH). Å It is initiated during the embryonic development stage when two million gamete mother cells (oogonia) are formed in each foetal ovary. Oogonia start meiotic division which gets arrested at prophase-I stage. They are referred to as primary oocytes. Each oocyte gets surrounded by the layers of granulosa cells that nourish it. Oocyte along with the cell layers around, is called primary follicle. More layers of granulosa cells and another theca layer surround it and now it is called secondary follicle. Secondary follicle transforms into tertiary follicle that has a fluid-filled cavity called antrum. The primary oocyte within the tertiary follicle grows in size and completes its first meiotic division now. This is an unequal division that results in the formation of a large haploid cell called secondary oocyte and a tiny cell called first polar body. Secondary oocyte keeps nearly all the nutrient rich cytoplasm, leaving only a haploid nucleus to the polar body. The tertiary follicle undergoes certain changes to mature into Graafian follicle. The oocyte gets glycoprotein deposits that form a non-cellular coating called zona pellucida, around it. The Graafian follicle ruptures to release secondary oocyte (ovum) from the ovary. The release of haploid secondary oocyte from the ovary, under the influence of LH surge, is called ovulation. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 48 Å The first menstruation starts at puberty and is called menarche, while its stoppage around 50 years of age is called menopause. Å The menstruation and the related events are repeated every 28-29 days (in normal females) in a cyclical fashion, that is why it is called menstrual cycle. Å Changes in the levels of pituitary and ovarian hormones bring about the cyclical changes in the ovary and uterus during menstrual cycle. It takes place in ovaries. Chromosome number per cell 46 Foetal life 23 23 Birth childhood Puberty Fertilisation and Implantation Å A sperm during fertilisation comes in contact with the zona pellucida of the ovum and induces changes in the membrane, which blocks the entry of the other sperms. Thus, ensuring that only one sperm can fertilise an ovum, i.e. prevents polyspermy. Å The secretions of the acrosome help the sperm to enter into the cytoplasm of the ovum through zona pellucida and the plasma membrane. Corona radiata is the innermost layer of ovum. It is dissolved by corona-penetrating enzymes of acrosome. Å This induces the completion of meiotic division of the secondary oocyte. The secondary meiotic division results in the formation of a secondary polar body and a haploid ovum. Å The haploid nucleus of the sperm and that of ovum fuse together to form a diploid zygote. Å Sex of the baby is decided at this stage. After fusion of the male and female gametes, the zygote would carry either XX or XY depending on whether the sperm carrying X or Y fertilised the ovum. The zygote carrying XX would develop into a female baby and XY would form a male baby. Å The mitotic division starts as the zygote (fertilised ovum) moves through the isthmus of the oviduct towards the uterus, forming 2, 4, 8, 16 daughter cells called blastomeres. This process is called cleavage. Å During cleavage, the young embryo slowly moves down the Fallopian tube towards the uterus and events taking place are during this route are as follows Oogonia Mitosis and differentiation Primary oocyte Ist meiotic division (completed prior to ovulation) Secondary oocyte First Adult polar body reproductive life Second Ovum polar body Diagrammatic view of phases in oogenesis Menstrual Cycle Å The reproductive cycle in female primates is called menstrual cycle. Å The major events of menstrual cycle are n n n n Å Å Menstrual (bleeding) phase lasts for about 3-5 days. The endometrium lining of uterus breaks down due to the deficiency of progesterone. Blood vessels rupture, causing bleeding through vagina. Follicular (proliferative) phase lasts for about 14 days. The endometrium rebuilds, FSH and LH secretions increase that stimulate follicular development as well as secretion of oestrogen. Ovulatory phase occurs at about 14th day. Both LH and FSH attain a peak level. Maximum level of LH (LH surge) ruptures the Graafian follicle and thereby, release the ovum. Luteal (secretory) phase lasts for about 10 days. The remaining part of Graafian follicle transforms into corpus luteum, which secretes progesterone for the maintenance of endometrium. After menstruation, the process of ovulation will occur again and the same process follows in a time period of 28-29 days. Cyclic menstruation indicates the normal reproductive phase and it continues from menarche to menopause. NEET n n n n n The embryo with 8-16 blastomeres is called morula. But, it is not larger than a zygote. The morula continues to divide and transforms into blastocyst, as it moves further into the uterus. This process of transformation is called blastulation. The blastomeres in the blastocyst are arranged into an outer layer called trophoblast and the inner group of cells attached to trophoblast called the inner cell mass. The trophoblast layer then gets attached to the endometrium and the inner cell mass differentiates into the embryo. After attachment, the uterine cells divide rapidly and cover the blastocyst. As a result, the blastocyst becomes embedded in the endometrium of the uterus. This is called implantation and it leads to pregnancy (i.e. the time from conception to birth). KEY NOTES www.mediit.in 49 CHAPTER 03 > Human Reproduction Pregnancy and Embryonic Development Å Å Å After implantation, finger-like projections appear on the trophoblast called chorionic villi, which are surrounded by the uterine tissue and maternal blood. The chorionic villi and the uterine tissue become inter-digitated with each other and jointly form a structural and functional unit between foetus and maternal body called placenta. The placenta performs the following functions It facilitates the supply of oxygen and nutrients to the embryo. Å In humans, pregnancy lasts for 9 months and foetal heart is formed after one month of pregnancy. Å The first sign of growing foetus may be noticed by listening to the heart sound carefully through stethoscope. Å By the end of second month, the foetus develops limbs and digits. By the end of 12 weeks, major organ systems and external genitalia are well-developed. Å The first movement of the foetus and appearance of hair can be observed during the fifth month. Å By the end of 24 weeks (second trimester), the body is covered with fine hair, eyelids get separated and eyelashes are formed. Å By the end of nine months of pregnancy, the foetus becomes fully developed and is ready for delivery. n n n n n Å Å It aids in the removal of carbon dioxide and waste materials produced by the foetus. The placenta is connected to the embryo through the umbilical cord, which helps in the transport of substances to and from the embryo. Placenta also acts as an endocrine tissue and produces several hormones like human Chorionic Gonadotropin (hCG), human Placental Lactogen (hPL), oestrogen, progestogens, etc. In the later phase of pregnancy, hormone called relaxin is also secreted by the ovary. It is important to note that hCG, hPL and relaxin are produced in women only during pregnancy. Parturition and Lactation Å The time period during which the embryo remains in the uterus is called gestation period. It is about 9 months in humans. Å Vigorous contraction of the uterus at the end of pregnancy causes expulsion/delivery of the foetus. This process of delivery of the foetus (childbirth) is called parturition. It is induced by a complex neuroendocrine mechanism. Å The signals of parturition originate from the fully developed foetus and the placenta, which induce mild uterine contractions called foetal-ejection reflex. Immediately after implantation, the inner cell mass differentiates into three germ layers, i.e. ectoderm (outer layer), endoderm (inner layer) and mesoderm (develop between ectoderm and endoderm). n These three layers give rise to all tissues (organs) in adults. Inner cell mass contains stem cells which have the potency to give rise to all the tissues and organs. n End Products of Embryonic Germ Layers Ectoderm Mesoderm Endoderm Epidermis Dermis Lining of the digestive system Hair, nails, sweat glands All muscles of the body Lining of the respiratory system Brain and spinal cord Cartilage Urethra and urinary bladder Cranial and spinal nerves Bone Gall bladder Retina, lens and cornea of eye Blood Liver and pancreas Inner ear All other connective tissues Thyroid gland Epithelium of nose, mouth and anus Blood vessels Parathyroid gland Enamel of teeth Reproductive organs and kidneys Thymus n This triggers the release of oxytocin from the maternal pituitary. It promotes contractions of uterine muscles, which in turn stimulate further secretion of oxytocin. The stimulatory reflex between the uterine contraction and oxytocin secretion continues resulting in stronger contractions. This leads to the expulsion of the baby out of the uterus through the birth canal. Soon after the birth of baby, placenta is also expelled out of the uterus. Relaxin hormone relaxes the pelvic ligaments of mother to prepare for the childbirth. Å The mammary glands in females undergo differentiation during pregnancy. The production and release of milk by the mammary glands of female after birth of a young one is called lactation. Å The first milk, which comes out from the mother’s mammary glands just after childbirth is called colostrum. It is rich in proteins and energy along with the antibodies that provide passive immunity to the newborn. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 50 Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Male Reproductive System 1 Pouch in which testes are suspended outside the abdominal cavity, is (a) tunica albuginea (c) epididymis vasa efferentia by (b) inguinal canal (d) scrotum 2 Function of scrotum is to maintain the (a) (b) (c) (d) (b) 5-6 cm and 3-4 cm (d) 7-8 cm and 8-9 cm 4 How many compartments (approximately) are there in each human testis? (b) 300 (c) 350 (d) 400 5 Compartments in mammalian testes are called (a) testicular lobules (c) Sertoli cells (b) seminiferous tubules (d) interstitial cells 6 Testicular lobules contain (a) (b) (c) (d) 3-5 seminiferous tubules 2-6 seminiferous tubules 5-7 seminiferous tubules 1-3 seminiferous tubules 7 The seminiferous tubules of the testis is lined on its NEET 2019, 16 (a) Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus (b) Seminiferous tubules → Vasa efferentia → Epididymis → Inguinal canal → Urethra (c) Testis → Epididymis → Vasa efferentia → Vas deferens → Ejaculatory duct → Inguinal canal → Urethra → Urethral meatus (d) Testis → Epididymis → Vasa efferentia → Rete testis → Inguinal canal → Urethra 13 Choose the incorrect pair. (a) (b) (c) (d) Leydig cells — Secrete testicular hormone Vasa efferentia and epididymis — Accessory ducts Vas deferens — Loops over the urinary bladder Ejaculatory duct — Vasa efferentia and seminal vesicle 14 Choose the correct option. C AIIMS 2019 B D inside by (a) spermatocytes (c) cells of Sertoli (b) rete testis (d) seminiferous tubules cells in male reproductive system. 3 Approximate length and width of testis are (a) 250 (a) vasa deferentia (c) epididymis 12 Select the correct sequence for transport of sperm temperature of testes body temperature level of growth hormone level of male hormone (a) 4-5 cm and 2-3 cm (c) 6-7 cm and 4-5 cm 11 The seminiferous tubules of the testis open into the (b) spermatogonia (d) Both (b) and (c) 8 ……… provide nutrition to the male germ cells. (a) (b) (c) (d) Interstitial cells Leydig cells Sertoli cells Both (a) and (b) A 9 Which of the following cells present in the mammalian testes forms the sperms? (a) Leydig cells (c) Interstitial cells (b) Spermatogonia (d) Sertoli cells (a) A– Testis–possesses 3-4 testicular lobule (b) B– Seminal vesicle–storage of sperm (c) C– Vas deferens–helps in sperm transfer (d) D– Prostate gland–secretes seminal fluid 15 The shared terminal duct of the reproductive and urinary system in the human male is CBSE-AIPMT 2014 10 Region outside the seminiferous tubules is called (a) interdigital space (c) interstitial space (b) interferous space (d) blind space (a) urethra (c) vas deferens (b) ureter (d) vasa efferentia www.mediit.in CHAPTER 03 > Human Reproduction 16 Identify A, B, C and D in the given diagram. A C D B 51 (a) A–Sertoli cells, B–Spermatozoa, C–Interstitial cells, D–Sperms (b) A–Sertoli cells, B–Secondary spermatocyte, C–Interstitial cells, D–Spermatozoa (c) A–Interstitial cells, B–Spermatogonia, C–Sertoli cells, D–Sperms (d) A–Sertoli cells, B–Spermatogonia, C–Interstitial cells, D–Spermatozoa 19 The given digaram shows LS of testis showing various parts. Identify the parts labelled (A-G) from the list given below. A (a) A–Urinary bladder, B–Bulbourethral gland, C–Prostate gland, D–Seminal vesicles (b) A–Urinary bladder, B–Urethra, C–Vas deferens, D–Bulbourethral gland (c) A–Prostate gland, B–Seminal vesicles, C–Urinary bladder, D–Bulbourethral gland (d) A–Bulbourethral gland, B–Urinary bladder, C–Seminal vesicles, D–Prostate gland 17 Identify the accessory glands found in males. (a) Seminal vesicles (c) Bulbourethral gland (b) Prostate gland (d) All of these 18 The given diagram refers to TS of testis showing sectional view of a few seminiferous tubules. Identify the parts labelled A-D and select the correct option. D A B C B G C D F I. II. III. IV. V. VI. VII. VIII. IX. X. E Caput epididymis Cauda epididymis Vas deferens Vasa efferentia Corpus epididymis Seminiferous tubules Tunica vaginalis Tunica albuginea Tunica vasculosa Rete testis Codes A (a) II (b) V (c) I (d) I B III IV IV VI C IV III X IV D X VI III III E VI I II V F I X VI X G IX VII VIII IX TOPIC 2 ~ Female Reproductive System 20 The ovaries are located one on each side of the…A…. Each ovary is about 2-4 cm in length connected to the …B… wall by …C… . Each ovary is covered by a thin epithelium which encloses the ovarian stroma. Stroma is divided into two zones …D… and …E… . Fill the suitable choices for A-E. (a) A–inner medulla, B–peripheral cortex, C–ligaments, D–pelvic wall, E-lower abdomen (b) A–lower abdomen B–pelvic, C–ligaments, D–peripheral cortex, E–inner medulla (c) A–pelvic wall, B–lower abdomen, C–ligaments, D–inner medulla, E–peripheral cortex (d) A–inner medulla, B–peripheral cortex, C–lower abdomen, D–pelvic wall, E–ligaments 21 The following diagram refers to female reproductive system of human. Identify A to E. D A B C E (a) A–Urethra, B–Urinary bladder, C–Uterus, D–Cervix, E–Vagina (b) A–Urethra, B–Urinary bladder, C–Uterus, D–Vagina, E–Cervix (c) A–Urethra, B–Urinary bladder, C–Uterus, D–Cervix, E–Vagina (d) A–Uterus, B–Urinary bladder, C–Urethra, D–Cervix, E–Vagina www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 52 22 Oviducts are also called (a) Fallopian tubes (c) vagina 31 Given the diagrammatic sectional view of mammary gland. Identify A, B, C and D. (b) uterus (d) ovary 23 Human Fallopian tube is about (a) 8-9 cm long (c) 10-12 cm long A (b) 9-10 cm long (d) 12-17 cm long B 24 Funnel-shaped part of oviduct closer to the ovary is C called (a) fimbriae (c) ampulla (b) infundibulum (d) isthmus 25 Fimbriae are associated with which organ? (a) Fallopian tube (c) Vagina 26 The main function of fimbriae of Fallopian tube is (a) (b) (c) (d) help in development of ovary help in collection of the ovum after ovulation help in development of ova help in fertilisation 27 Choose the incorrect pair. (a) (b) (c) (d) Finger-like projections – Fimbriae Narrow part of oviduct – Ampulla Part of oviduct joining the uterus – Isthmus None of the above 28 The following diagram refers to the female reproductive system of humans. Identify A-F. F A B C D E (a) A–Ampulla, B–Isthmus, C–Infundibulum, D–Fallopian tube, E–Ovary, F–Uterine fundus (b) A–Isthmus, B–Infundibulum, C–Ampulla, D–Fallopian tube, E–Ovary, F–Uterine fundus (c) A–Isthmus, B–Ampulla, C–Infundibulum, D–Fallopian tube, E–Ovary, F–Uterine fundus (d) A–Ampulla, B–Infundibulum, C–Isthmus, D–Fallopian tube, E–Ovary, F–Uterine fundus 29 Choose the incorrect pair. (a) Cushion of fatty tissue covered by pubic hair –Mons pubis (b) Membrane covering opening of vagina–Hymen (c) Finger-like structure above the urethral opening –Clitoris (d) Uterine layer exhibiting strong contraction during delivery–Endometrium 30 The main tissue present in breast is ……… tissue. (a) glandular (c) ciliated (b) squamous (d) epithelium D JIPMER 2018 (b) Uterus (d) Ovary (a) A–Alveolus, B–Mammary duct, C–Lactiferous duct, D–Areola (b) A–Alveolus, B–Lactiferous duct, C–Mammary duct, D–Areola (c) A–Alveolus, B–Mammary duct, C–Lactiferous duct, D–Lactogenic spot (d) A–Fat, B–Mammary duct, C–Lactiferous duct, D–Areola 32 Several mammary ducts join to form a wider mammary ampulla, which is connected to (a) (b) (c) (d) lactiferous duct seminiferous duct seminiferous tubules nipple 33 Pick the odd one out from each series given below and select the correct option. I. Scrotum, rete testis, Fallopian tube, vas deferens. II. Ovary, uterus, vagina, ejaculatory duct. III. Acrosome, Graafian follicle, corpus luteum, cervix. IV. Prostate, testis, seminal vesicles, Cowper’s gland. I (a) Vas deferens (b) Rete testis (c) Scrotum (d) Fallopian tube II Vagina Ovary III Cervix Graafian follicle Uterus Corpus luteum Ejaculatory Acrosome duct IV Cowper’s gland Prostate Seminal vesicles Testis 34 A sectional view of mammary gland shows I. nipple and areola. II. mammary lobes (alveolus) and duct. III. ribs. IV. ampulla and lactiferous duct. Choose the correct option from the above. (a) I, II, III and IV (c) III, IV and II (b) I, II and III (d) I, IV and III www.mediit.in CHAPTER 03 > Human Reproduction 53 TOPIC 3 ~ Gametogenesis 35 Number of chromosomes present in 44 The difference between spermiogenesis and spermatogonium is (a) 46 (b) 23 JIPMER 2019 (c) 48 (d) 43 36 Which cells come earliest in the sequence of sperm production? (a) Spermatozoa (c) Spermatid (b) Spermatocyte (d) Spermatogonia 37 Which of the following undergoes meiosis-I division during spermatogenesis? (a) Primary spermatocytes (b) Secondary spermatocytes (c) Sertoli cell (d) Leydig cell 38 Number of chromosomes present in secondary spermatocyte is (a) 22 (b) 23 JIPMER 2019 (c) 24 (d) 25 39 Which one of the following cells have haploid number of chromosome? (a) Primary spermatocytes (b) Secondary spermatocytes (c) Spermatid (d) Both (b) and (c) 40 During spermatogenesis, which cells are the first to contain haploid number of chromosomes? (a) (b) (c) (d) Spermatogonium Primary spermatocyte Secondary spermatocyte Spermatid 41 Find out spermatid and Sertoli cell in given below diagram. spermiation is NEET 2018 (a) in spermiogenesis, spermatozoa from Sertoli cells are released into the cavity of seminiferous tubules, while in spermiation, spermatozoa are formed (b) in spermiogenesis, spermatozoa are formed, while in spermiation, spermatids are formed (c) in spermiogenesis, spermatids are formed, while in spermiation, spermatozoa are formed (d) in spermiogenesis, spermatozoa are formed, while in spermiation, spermatozoa are released through seminiferous tubules 45 Spermatogenesis starts at puberty due to significant increase in the secretion of (a) GnRH (c) testosterone (b) prolactin (d) oestrogen 46 GnRH, a hypothalamic hormone, needed in reproduction, acts on NEET 2017 (a) anterior pituitary gland and stimulates secretion of LH and oxytocin (b) anterior pituitary gland and stimulates secretion of LH and FSH (c) posterior pituitary gland and stimulates secretion of oxytocin and FSH (d) posterior pituitary gland and stimulates secretion of LH and relaxin 47 Give the name of two hormones A and B in the figure given below. A A B Acts on Leydig cells (a) FSH and GH (c) GH and LH C D Secrete B Stimulate spermatogenesis (b) LH and androgens (d) GH and lactin 48 Sperms of mammals depend for movement on E (a) only tail (c) middle piece F (b) tail and middle piece (d) Only head 49 Which one of the labelled part utilises fructose as a source of energy? (a) D and E (b) E and F (c) A and C (d) B and E Head 42 Spermiogenesis is (a) (b) (c) (d) spermatids transformed into spermatozoa spermatozoa transformed into spermatids spermatozoa transformed to spermatocytes spermatid to secondary spermatocytes JIPMER 2019 Acrosome Nucleus Middle piece Tail 43 What is the correct sequence of sperm formation? NEET 2013 (a) Spermatid, Spermatocyte, Spermatogonia, Spermatozoa (b) Spermatogonia, Spermatocyte, Spermatozoa, Spermatid (c) Spermatogonia, Spermatozoa, Spermatocyte, Spermatid (d) Spermatogonia, Spermatocyte, Spermatid, Spermatozoa (a) Head (c) Acrosome (b) Tail (d) Middle piece www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 54 50 Choose the incorrect pair. (a) Acrosome – Enzyme filled cap structure on sperm head (b) Middle piece – Possesses numerous mitochondria (c) Sperm tail – Facilitates sperm motility essential for fertilisation (d) Semen – Contains only sperms 51 Choose the incorrect pair. D F (a) Primary follicle Secondary follicle Corpus luteum (b) Secondary follicle Graafian follicle Corpus luteum (c) Tertiary follicle Primary follicle Secondary follicle (d) Tertiary follicle Graafian follicle Corpus luteum 56 Identify A, B and C in the figure given below. (a) Antrum – Fluid-filled cavity in primary follicle (b) Tertiary follicle – Primary oocyte completes its Ist meiotic division inside it (c) Secondary oocyte – Haploid cell formed after Ist meiotic division (d) Graafian follicle – Mature tertiary follicle which ruptures during ovulation A I Foetal life B secondary oocyte is called zona granulosa zona pellucida plasma membrane tertiary membrane Adult reproductive life 53 Which of the following layers in an antral follicle is acellular? CBSE-AIPMT 2015 (a) Granulosa (c) Stroma (b) Theca interna (d) Zona pellucida 54 At which stage of the development, ovum is released (b) Oogonium (d) Ootid 55 Consider the figure given below. C B (a) (b) (c) (d) C First polar body III Ovum Second polar body A–Secondary oocyte, B–Oogonia, C–Primary oocyte A–Oogonia, B–Primary oocyte, C–Secondary oocyte A–Secondary oocyte, B–Primary oocyte, C–Oogonia A–Oogonia, B–Secondary oocyte, C–Primary oocyte 57 Mark the wrong item in each series and select the from the ovary of the human female? (a) Primary oocyte (c) Secondary oocyte II Birth Childhood Puberty 52 The new membrane formed by follicular cells in (a) (b) (c) (d) C A D correct option. I. Spermatocyte, polar body, spermatid, spermatogonium II. Endometrium, corpus luteum, acrosome, Graafian follicle III. Vas deferens, Fallopian tube, epididymis, Cowper’s gland IV. Testes, prostate, seminal vesicles, Cowper’s gland I (a) Spermatid E F Select the option which correctly identifies the parts labelled as C, D and F. II III IV Endometrium Epididymis Prostate (b) Polar body Acrosome Testes (c) Spermatocyte Corpus luteum Vas deferens (d) Spermatogonium Graafian follicle Fallopian tube Cowper’s gland Cowper’s gland Seminal vesicles TOPIC 4~ Menstrual Cycle 58 The reproductive cycle in the female primates such as 60 Menstrual flow occurs due to the lack of monkeys, apes and human beings is called (a) menstrual cycle (c) circadian cycle (b) oestrus cycle (d) ovulatory cycle 59 The first menstruation that begins at puberty is called (a) menopause (c) gametogenesis (b) ovulation (d) menarch CBSE-AIPMT 2012 (a) progesterone (c) oxytocin (b) FSH (d) vasopressin 61 In an ideal menstrual cycle, the menstrual phase last for (a) 3-5 days (b) 5-6 days (c) 1-3 days (d) 2-3 days www.mediit.in CHAPTER 03 > Human Reproduction 55 62 A regular cycling woman is not menstruating, which 71 The main function of mammalian corpus luteum is to one of the following is the most likely to be the root cause? (a) Maintenance of the hypertrophical endometrial lining (b) Maintenance of high concentration of sex-hormones in the bloodstream (c) Regression of well-developed corpus luteum (d) Fertilisation of the ovum produce 72 Endometrium, epithelial glands and connective tissue of uterus are broken due to the 63 What happens during the follicular phase of (a) lack of oestrogen (c) lack of FSH menstrual cycle? (a) (b) (c) (d) Proliferation of endometrium Reduction in blood supply to endometrium Regression of endometrium No effect on endometrium 64 Level of LH is maximum one of the following is likely to happen? (a) (b) (c) (d) JIPMER 2019 (a) Proliferative phase–Rapid regeneration of myometrium and maturation of Graafian follicle (b) Secretory phase–Development of corpus luteum and increased secretion of progesterone (c) Menstruation–Breakdown of endometrium (d) Ovulation–LH and FSH attain peak level and cause rupture of Graafian follicle female? (b) 14-16 days (d) 20-26 days 66 Rapid secretion of LH in ovulatory phase causes rupturing of Graafian follicle release of ova ovulation All of the above 75 Correct sequence of secretion of hormone from beginning of menstrual cycle to the end is (a) (b) (c) (d) 67 Which of the following events is not associated with ovulation in human female? (a) (b) (c) (d) Corpus luteum will degenerate Oestrogen secretion further decreases Primary follicle starts developing Progesterone secretion rapidly increases 74 Which of them is not a correct match? 65 When does ovulation occur in a healthy menstruating (a) (b) (c) (d) (b) lack of progesterone (d) excess of FSH 73 If the mammalian ovum fails to get fertilised, which (a) just before ovulation (b) just after ovulation (c) at the time of ovulation (d) during menstrual bleeding phase (a) 9-14 days (c) 16-28 days CBSE-AIPMT 2014, 1995 (a) oestrogen only (b) progesterone only (c) human chorionic gonadotropin (d) relaxin only CBSE-AIPMT 2015 FSH, progesterone, LH oestrogen, FSH and progesterone FSH, oestrogen, progesterone oestrogen, progesterone, FSH 76 Read the graph and correlate the uterine events that Decrease in oestradiol Full developement of Graafian follicle Release of secondary oocyte LH surge take place according to the hormonal levels on A. 6-15 days, B. 16-25 days, C. 3-5 days (if the ovum is not fertilised). menstrual cycle because (a) (b) (c) (d) NEET (Odisha) 2019 follicles do not remain in the ovary after ovulation FSH levels are high in the luteal phase LH levels are high in the luteal phase Both (b) and (c) 69 Formation of corpus luteum is induced by JIPMER 2018 (a) LH (b) oestrogen (c) FSH (d) progesterone Oestrogen Progesterone 1 70 A temporary endocrine gland in the human body is NEET 2017 (a) pineal gland (c) corpus luteum Ovarian hormone levels 68 No new follicles develop in the luteal phase of the (b) corpus cardiacum (d) corpus allatum 5 10 15 Days 20 25 29 (a) A–Degeneration of endometrium, B–Myometrium thickness, becomes vascularised ready to receive and implant embryo, C–Regeneration of endometrium (b) A–Degeneration of endometrium, B–Endometrium thickness increases, becomes vascularised, ready to receive and implant ovum, C–Regeneration of endometrium www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 56 (c) A–Regeneration of endometrium, B–Endometrium becomes thick and vascularised ready to receive and implant embryo, C–Degeneration of endometrium (d) A–Regeneration of myometrium, B–Endometrium becomes thick and vascularised, ready to receive and implant embryo, C–Degeneration of endometrium 77 The following graph of relative concentrations of the C A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2122 23 24 25 26 27 28 Days (a) (b) (c) (d) High High (b) High (c) Low (d) Low High Low Low High Low High (a) A–FSH, B–Progesterone, C–LH, D–Oestrogen A–LH, B–Progesterone, C–FSH, D–Oestrogen A–FSH, B–Oestrogen, C–LH, D–Progesterone A–LH, B–Oestrogen, C–FSH, D–Progesterone Increasing thickness of endometrium endometrium during a normal menstruation. Identify A and B. B 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Days (a) (b) (c) (d) Progesterone Low High Low High Low Low High Low hormone concentration which occurs during the menstrual cycle. Match A, B, C, D, E, F, G and H of graph with the hormones and events given below. A B C FSH 0 7 14 21 D 0 7 14 Time/days F A (a) IV (b) VIII (c) VIII (d) I E 21 G Hormones and Events I. Oestrogen II. III. Repair of endometrium IV. V. Menstruation VI. VII. Progesterone VIII. B I III VI III C VI IV IV V D V II I VII 28 28 H Ovulation Luteinizing hormone Luteal phase Ovarian phase E F G III VIII VII I VI VII VII III II VIII VI IV H II V V II 81 Some important events in the human female A–Ovulation, B–Menopause A–Ovulation, B–Menstruation A–Menstruation, B–Ovulation A–Menopause, B–Ovulation 79 The events of the menstrual cycle are represented below. In which of the following options the level of FSH, LH and progesterone is mentioned correctly? Proliferative phase or Follicular phase (5-15 days) Menstruation (1-5 days) Low High High LH 80 The diagram shows some of the changes in blood 78 The diagram shows the changes that take place in the A LH D B 20-28 Days Proges FSH -terone Low Low FSH Hormone concentration in the blood/arbitrary units Increasing concentration of hormone four hormones present in the blood plasma of a woman during her menstrual cycle. Identify the hormones A, B, C and D. 13-14 Days Luteal phase or Secretory phase (16-28 days) reproductive cycle are given below. Arrange the events in proper sequence. I. Secretion of FSH. II. Growth of corpus luteum. III. Growth of the follicle and oogenesis. IV. Ovulation. V. Sudden increase in the levels of LH. Choose the correct option. (a) (b) (c) (d) III → I → IV → II → V I → III → V → IV → II I → IV → III → V → II II → I → III → IV → V 82 Cessation of menstrual cycle at the age of 50 is called (a) ovulation (c) menses (b) gametogenesis (d) menopause www.mediit.in CHAPTER 03 > Human Reproduction 57 TOPIC 5 ~ Fertilisation and Implantation 83 Capacitation occurs in (a) rete testis (c) vas deferens NEET 2017 (b) epididymis (d) female reproductive tract 84 Fertilisation in humans is practically feasible only if NEET 2016 (a) the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the Fallopian tube (b) the ovum and sperms are transported simultaneously to ampullary-isthmic junction of the cervix (c) the sperms are transported into cervix within 48 hrs of release of ovum in uterus (d) the sperms are transported into vagina just after the release of ovum in Fallopian tube 91 Cleavage is the rapid mitotic division occurring on the way through isthmus to oviduct. It occurs in (a) gametes (c) sperm (b) zygote (d) ova 92 Cleavage forms 2-4-8-16 cells. These cells are called (a) blastocysts (c) morula (b) blastomeres (d) trophoblast 93 Embryo at 8-16 cells stage is called (a) blastula (c) trophoblast (b) morula (d) All of these 94 Study the chart given below. Blastocyst Contains two types of cell 85 Everytime copulation does not lead to fertilisation and pregnancy because of failure of sperm to reach the (a) ampulla (c) endometrium (b) cervix (d) myometrium A 86 During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of …A… . The secretions of the …B… help the sperm enter into the cytoplasm of the ovum. (a) (b) (c) (d) A eggs eggs additional sperms additional sperms B zona pellucida acrosome acrosome zona pellucida 87 What is acrosomal reaction? B Select the option containing the correct identify of A and B. (a) (b) (c) (d) A–Trophoblast, B–Inner cell mass A–Placenta, B–Embryoblast A–Placenta, B–Trophoblast None of the above 95 Trophoblast of blastocyst attaches to the (a) endometrium (c) perimetrium JIPMER 2018 (a) Contact of sperms with eggs (b) Digestion of zona pellucida (c) Disintegration of acrosome (d) Contact of acrosome and nucleus of egg (b) myometrium (d) mesoderm 96 Inner cell mass or embryoblast gives rise to (a) foetal part (c) notochord (b) embryo (d) nourishment cell 97 The given diagram refers to ovum surrounded by few sperms. Identify A, B and C in the diagram. 88 Extrusion of second polar body from egg nucleus occurs NEET 2019 (a) after fertilisation (b) before the entry of sperm into ovum (c) simultaneously with first cleavage (d) after the entry of sperm but before fertilisation 89 In human females, meiosis-II is not complete until CBSE-AIPMT 2014 (a) puberty (c) uterine implantion (b) fertilisation (d) birth 90 The sex of the foetus will be decided at (a) (b) (c) (d) fertilisation by male gamete implantation fertilisation by female gamete the start of cleavage C A B (a) A–Zona pellucida, B–Perivitelline space, C–Corona reticulata (b) A–Zona pellucida, B–Vitelline membrane, C–Corona radiata (c) A–Zona pellucida, B–Perivitelline space, C–Corona radiata (d) A–Oolemma, B–Perivitelline space, C–Corona radiata www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 58 98 Consider the figure given below which depicts the 99 Identify A and B and their respective functions. sequence of embryonic development in humans. Identify E and G. A B A B C D E A B (a) Trophoblast Inner cell mass F (a) (b) (c) (d) E Morula Morula Gastrula Gastrula (b) Inner cell mass G G Blastula Blastocyst Blastocyst Blastula Function of A Function of B Gets attached to Differentiated as the endometrium embryo Trophoblast Gets attached to Differentiated as the endometrium embryo (c) Trophoblast Inner cell mass Differentiated as Gets attached to embryo the endometrium (d) Ectoderm Differentiated as Gets attached to embryo the endometrium Endoderm TOPIC 6 ~ Pregnancy and Embryonic Development 100 After implantation, finger-like projections appear on the trophoblast called … A… . They are surrounded by … B… and maternal blood. Here, A and B refer to (a) (b) (c) (d) A–chorion, B–foetal cell A–chorionic villi, B–uterine tissue A–uterine tissue, B–chorionic villi A–foetal cell, B–chorion 101 Chorionic villi and uterine tissue become interdigitated with each other and jointly form (a) trophoblast (c) placenta (b) inner cell mass (d) embryo 102 In the given diagram, find out A, B and C. B (c) A–Umbilical cord, B–Plug of mucus in cervix, C–Placental villi (d) A–Placental villi, B–Plug of mucus in cervix,C–Umbilical cord 103 Several hormones like hCG, hPL, oestrogen, progesterone are produced by (a) ovary (c) Fallopian tube NEET 2016 (b) placenta (d) pituitary 104 Hormones secreted by the placenta to maintain pregnancy are (a) (b) (c) (d) NEET 2018 hCG, hPL, progestogens, oestrogens hCG, hPL, oestrogens, relaxin, oxytocin hCG, hPL, progestogens, prolactin hCG, progestogens, oestrogens, glucocorticoids 105 Which one is present in the urine of pregnant woman? JIPMER 2018 (a) hCG A (b) LH (c) Oestrogen (d) FSH 106 Structure analogous to the placenta in mammals. JIPMER 2019 (a) Chorion C (a) A–Plug of mucus in cervix, B–Placental villi C–Umbilical cord (b) A–Umbilical cord, B–Placental villi,C–Plug of mucus in cervix (b) Amnion (c) Yolk sac (d) Allantois 107 Relaxin (a hormone) is secreted by (a) (b) (c) (d) placenta ovary anterior lobe of pituitary posterior lobe of pituitary www.mediit.in CHAPTER 03 > Human Reproduction 59 108 Soon after implantation, the inner cell mass 111 Gastrulation means differentiates into outer …A…, middle …B… and an inner …C… . A, B and C in the given sentence are (a) (b) (c) (d) A–mesoderm, B–ectoderm, C–endoderm A–ectoderm, B–mesoderm, C–endoderm A–ectoderm, B–endoderm, C–mesoderm A–mesoderm, B–endoderm, C–ectoderm 112 The correct sequence is 109 Identify the correctly matched pair/pairs of the germ layers and their derivatives. I. Ectoderm – Epidermis II. Endoderm – Dermis III. Mesoderm – Muscles IV. Mesoderm – Cartilage V. Endoderm – Enamel of teeth Choose the option containing the correctly matched pairs. (a) I and IV (b) I and II (c) I, III and IV (d) I, II, III and V 110 The amnion of mammalian embryo is derived from (a) (b) (c) (d) NEET 2018 mesoderm and trophoblast endoderm and mesoderm ectoderm and mesoderm ectoderm and endoderm JIPMER 2019 (a) conversion of blastula into morula (b) formation of three germ layers (c) a phase in which organogenesis takes places (d) a phase chracterised by inner cell mass JIPMER 2018 (a) Zygote → Cleavage → Morula → Blastula → Gastrula (b) Cleavage → Zygote → Morula → Blastula → Gastrula (c) Zygote → Morula → Blastula → Cleavage → Gastrula (d) Zygote → Blastula → Morula → Cleavage → Gastrula 113 Choose the incorrect pair. Time of development in foetus Organ (a) Heart After one month of pregnancy (b) Limbs and digits By the end of second month (c) External genital organs By the end of 24 weeks (second trimester) (d) First movement of foetus During the fifth month TOPIC 7 ~ Parturition and Lactation 114 Parturition is induced by 118 Which one of the following is not the function of placenta? It (a) neural mechanism (b) endocrine mechanism (c) neuroendocrine mechanism (d) hormonal mechanism 115 Signals for parturition originate from CBSE-AIPMT 2012, 10 116 Identify the correct sequence in which the various stages of parturition take place. (a) Shedding of placenta → Dilation of cervix → Delivery of the baby (b) Dilation of the cervix → Shedding of placenta → Delivery of the baby (c) Dilation of the cervix → Delivery of the baby → Shedding of placenta (d) None of the above 117 Which of the following hormones is responsible for both the milk-ejection reflex and the foetal-ejection NEET (Odisha) 2019 reflex? (a) Oestrogen (c) Oxytocin (b) Prolactin (d) Relaxin 119 Name A, B and C hormones in the given figure. A From ovaries Induces oxytocin receptors on uterus B From mother’s posterior pituitary Stimulates uterus to contract Stimulates placenta to make C Stimulates more contractions of uterus (a) (b) (c) (d) Positive feedback (a) Both placenta as well as fully developed foetus (b) oxytocin released from maternal pituitary (c) placenta (d) fully developed foetus NEET 2013 (a) facilitates supply of oxygen and nutrients to embryo (b) secretes oestrogen (c) facilitates removal of carbon dioxide and waste material from embryo (d) secretes oxytocin during parturition A–Prostaglandin, B–Oxytocin, C–Oestrogen A–Oestrogen, B–Oxytocin, C–Prostaglandin A–Oestrogen, B–Prostaglandin, C–Oxytocin A–Prostaglandin, B–Oestrogen, C–Oxytocin 120 Colostrum is important for newly born because (a) (b) (c) (d) it contains essential antigen it contains essential antibodies Both (a) and (b) it has more nutrients than ordinary milk www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 60 NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason 128 Assertion (A) Menstrual phase is also compared to ■ Direction (Q. No. 121-135) In each of the following questions, a statement of Assertion (A) is given and followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of the A (b) If both A and R are true, but R is not the correct explanation of the A (c) If A is true, but R is false (d) If A is false, but R is true 129 130 121 Assertion (A) The testes are situated outside the 122 123 124 125 126 127 abdominal cavity within scrotum. Reason (R) Muscles in scrotum helps to maintain low temperature of testes, necessary for spermatogenesis. Assertion (A) In the testis, spermatogenesis occurs in the seminiferous tubules and testosterone secretion takes place from the Sertoli cells. Reason (R) Testosterone brings growth and maturation of secondary sex organs and also the development of accessory sex characters. Assertion (A) The Sertoli cells are present in seminiferous tubules. Reason (R) Sertoli cells provide nutrition to the germ cells and spermatozoa. Assertion (A) The bulbourethral gland is a male accessory gland. Reason (R) Its secretion helps in the lubrication of the penis, thereby facilitating reproduction. Assertion (A) Fimbriae are finger-like projections of infundibulum part of oviduct which is closest to ovary. Reason (R) They are important for the collection of ovum after ovulation from ovary. Assertion (A) In females, parturition is the act of giving birth to a baby. AIIMS 2018 Reason (R) Signals for parturition originate from a fully developed foetus. Assertion (A) Ovum retains most of the contents of the primary oocyte and is much larger than a spermatozoa. Reason (R) Ovum needs energy to go about in search of a spermatozoa for fertilisation. 131 132 133 134 135 shedding tears for the lost ovum. Reason (R) In the menstrual phase, loss of endometrial lining takes place due to reduced titre of progesterone. Assertion (A) Production of FSH and LH increases in the ovulation phase. Reason (R) Due to decrease in the level of LH ovulation (releasing of ova) takes place. Assertion (A) Progesterone is essential for maintenance of the endometrium. Reason (R) Endometrium is essential for implantation of fertilised ovum. Assertion (A) Not all copulations lead to pregnancy. Reason (R) Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary-isthmic junction. Assertion (A) In humans, the gamete contributed by the male determines whether the child produced will be male or female. Reason (R) Sex in humans is a polygenic trait, depending upon a cumulative effect of some genes on X-chromosome. Assertion (A) Placenta is an endocrine gland. Reason (R) It secretes many hormones essential for pregnancy. Assertion (A) The presence of hCG in woman urine is the basis for pregnancy test. Reason (R) A woman passes out hCG in the urine during pregnancy. Assertion (A) Breastfeeding during initial period of infant growth is recommended. Reason (R) Colostrum contains several antibodies, essential to render immunity in newborns. II. Statement Based Questions 136 Choose the correct statement. (a) Size of testis is 4-5 cm in length and 1 cm in width (b) The scrotum is maintained at body temperature (c) The testes are situated outside the abdominal cavity in humans (d) The earliest stages of spermatogenesis occur outside the testis www.mediit.in CHAPTER 03 > Human Reproduction 137 Choose the incorrect statement (s). (a) Oogonia are formed and added after birth (b) Oogenesis is initiated during the embryonic development (c) No more gamete mother cells are formed in females after birth (d) All of the above 138 Which of the following statement is incorrect? (a) Each ovary is about 2 to 4 cm in length and is connected to the pelvic wall and uterus by ligaments (b) Each ovary is covered by a thin epithelium which encloses the ovarian stroma (c) Ovaries produce several steroid hormones only (d) the stroma of ovary is divided into a peripheral cortex and an inner medulla 139 Read the following statements. I. The uterus is present in single pair and is also called womb. II. The shape of uterus is like an inverted pear. III. The uterus opens into vagina through a narrow cervix. IV. Birth canal is formed by cervical canal and vagina. V. Perimetrium of uterus wall is external and thick, myometrium is middle thin layer of smooth muscles and endometrium is inner glandular layer. Which of the above statements are correct ? (a) I, II and III (c) IV and V (b) II, III and IV (d) I and V 140 Read the following statements. I. Spermatogonia and spermatids are diploid. II. The extrusion of second polar body from nucleus occurs after the entry of sperm and completion of fertilisation. III. Spermatogenesis and sperm differentiation under the control of FSH and testosterone. IV. A change in ovum after penetration of sperm the formation of second polar body. V. The secondary oocyte in the Graaffian follicle forms a new membrane called zona pellucida surrounding it. Which of the above statements are correct? (a) I, II, III and V (c) Only III (b) I and III (d) II, III, IV and V 141 Read the following statements. I. Each testis has about 25 compartments called testicular lobules. II. Each testicular lobule contains one to three highly coiled seminiferous tubules in which sperms are produced. III. Sertoli cells act as nurse cells of testicles. IV. Sertoli cells are activated by FSH secreted by the adenohypophysis. Which of the above statements are incorrect? (a) I and III (b) Only I (c) II and IV (d) III and IV 61 142 Which of the following statement/s is not correct? (a) The external opening of penis is called urethral meatus (b) Glans penis is covered by loose fold of skin called foreskin (c) Secretion of bulbourethral gland helps in lubrication of penis (d) None of the above 143 Which of the following statement is false for uterus? (a) It is also called womb and its shape is like an inverted pear (b) It is supported by ligaments attached to the pelvic wall (c) It opens into oviducts through cervix whose cavity is called cervical canal (d) It is bound by three layers, outer perimetrium, middle myometrium and inner endometrium 144 Which one of the following statement is false in respect of viability of mammalian sperm? CBSE-AIPMT 2012 (a) Sperm is viable for only up to 24 hrs (b) Survival of sperm depends on the pH of the medium and is more active in alkaline medium (c) Viability of sperm is determined by its motility (d) Sperms must be concentrated in a thick suspension 145 Which of the following statement is not correct for oogonia? (a) (b) (c) (d) They are million gamete mother cells They are formed within each foetal ovary They are formed throughout the life of female They start division and get arrested at prophase-I of meiotic division 146 Select the incorrect statement. NEET 2016 (a) LH and FSH trigger ovulation in ovary (b) LH and FSH decrease gradually during the follicular phase (c) LH triggers secretion of androgens from the Leydig cells (d) FSH stimulates the Sertoli cells which help in spermiogenesis 147 Identify the correct statement(s) for placenta. (a) It facilitates the supply of O 2 and nutrients to embryo (b) It is connected to embryo through umbilical cord (c) It removes CO 2 and excretory material produced by embryo (d) All of the above 148 Identify the correct statement on ‘inhibin’. NEET 2016 (a) It is produced by granulosa cells in ovary and inhibits the secretion of FSH (b) It is produced by granulosa cells in ovary and inhibits the secretion of LH (c) It is produced by nurse cells in testes and inhibits the secretion of LH (d) It inhibits the secretion of LH, FSH and prolactin www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 62 149 Select the correct option describing gonadotropin activity in a normal pregnant female. CBSE-AIPMT 2014, 12 (a) High level of FSH and LH stimulates the thickening of endometrium (b) High level of FSH and LH facilitates implantation of the embryo (c) High level of hCG stimulates the synthesis of oestrogen and progesterone (d) High level of hCG stimulates the thickening of endometrium 150 Consider the following three statements related to the human male reproductive system and select the correct option stating which ones are True (T) and which ones are False (F). I. Middle piece of spermatozoon is also termed as power house of spermatozoon. II. Vas deferens joins a duct from seminal vesicle and form vasa efferentia. III. Semen is a collection of secretions from the seminal vesicles, prostate gland, Cowper’s glands and sperms from testes. I (a) T (c) T II F T III T F I (b) F (d) F II F T III T T 151 Read the following statements and select the correct option(s). I. Maintenance of hygiene and sanitation during menstruation is very important. II. Primary oocytes surrounded by a layer of granulosa cells and called primary follicle. III. Seminal plasma is rich in fructose, calcium and certain enzymes. IV. In females, uterus is single and also called womb. (a) Only I (c) Only III II. Each spermatogonium in seminiferous tubule is diploid and contains 46 chromosomes. (a) Both statements are incorrect (b) Statement I is correct, but statement II is incorrect (c) Both statements are correct (d) Statement I is incorrect, but statement II is correct. 154 Which of the following statements is correct? I. Oogenesis is initiated during the embryonic development stage . II. At puberty only 60, 000-80, 000 primary follicles are left in each ovary. III. The primary follicles surrounded with many layers of granulosa cells and form a new theca called secondary follicles. IV. Changing of sanitary napkins or pads after every 4-5 hours is necessary for maintaining menstrual hygiene. (a) I and II (c) I and III (b) I, II, III and IV (d) None of these 155 Regarding male pronucleus which among the following statement is correct? I. It is the sperm nucleus after entering the ovum at fertilisation. II. Both head and neck of sperm contribute to pronucleus formation. III. Male pronucleus contains mitochondria. IV. Sperm head contains pronucleus having diploid set of chromosomes. (a) Only II (b) III and IV (c) Only I (d) II and IV 156 Study the figure of the human female reproductive system given below. C (b) I and II (d) All of these D B 152 Given below are four statements (I-IV) regarding embryonic development in humans. I. Cleavage divisions bring about considerable increase in the mass of protoplasm. II. With more cleavage divisions, the resultant blastomeres become smaller and smaller. III. The blastomeres in the blastocyst are arranged into two layers, i.e. trophoblast and endometrium. IV. Cleavage divisions result in a solid ball of cells called morula. Which of the above two statements are correct? (a) I and III (b) II and IV (c) I and II (d) III and IV 153 Read the given statements and select the correct option. I. The production of sperms and ovum by the testis in males and the ovaries in female, respectively, called gametogenesis. E A Read the following statements and select the option containing the incorrect statement(s). I. A–ovary produces oestrogen required for the development of female primary sex characters. II. A–Vagina receives the penis during copulation. III. B–Uterus serves as the site for implantation of the fertilised egg. IV. C–Oviduct serves as the site for fertilisation of the egg. (a) I and II (c) Only II (b) Only I (d) II and IV www.mediit.in CHAPTER 03 > Human Reproduction 63 III. Matching Type Questions 161 Match the following columns. Column I (Layers of uterus) 157 Match the following columns. Column I (Events) Column II (Features) Column II (Features) A. Perimetrium 1. Inner glandular layer of uterus A. Parturition 1. Attachment of zygote to endometrium B. Endometrium 2. External thin membrane of uterus B. Gestation 2. Release of egg C. Myometrium 3. Middle thick membrane of uterus C. Ovulation 3. Delivery of baby D. Implantation 4. Period between fertilisation and the birth E. Fertilisation 5. Fusion of male and female gametes Codes A (a) 2 (c) 3 Codes A (a) 2 (b) 4 (c) 5 (d) 3 B 4 3 1 4 C 1 1 2 2 D 5 5 3 1 Column II A. Testis 1. Gives specific constituents to semen B. Vulva 2. Oogenesis C. Prostate fluid 3. Scrotum Codes A (a) 3 (c) 4 C 1 2 D 2 1 B 2 3 C 3 1 D 1 2 Column II (Related to) A. Ovaries 1. Fertilisation B. Oviduct 2. Ovulation C. Uterus 3. Pregnancy D. Cervix 4. Childbirth A (b) 1 (d) 2 B 2 3 C 3 1 Column II 1. Breakdown of endometrial lining B. Secretory phase 2. Follicular phase C. Menstruation 3. Luteal phase Codes A (a) 2 (c) 3 B 3 2 C 1 1 A (b) 1 (d) 3 D 4 2 C 3 4 Column I D 4 1 Column II A. Acrosome 1. Rudimentary tissue B. Endometrium 2. Uterus C. Polar body 3. Oogenesis D. Clitoris 4. Spermatozoa B 1 2 C 4 1 B 3 1 C 2 2 D 3 3 A (b) 4 (d) 4 B 2 3 C 3 1 D 1 2 Column II (Names) A. Stage-I 1. Menstrual phase B. Stage-II 2. Follicular proliferative C. Stage-III 3. Ovulatory phase D. Stage-IV 4. Luteal/Secretory phase Codes A (a) 4 (b) 4 (c) 1 (d) 4 160 Match the following columns. Codes A (a) 2 (c) 4 NEET 2018 163 Match the following columns. A (b) 4 (d) 4 Column I (Female reproductive parts) B 1 3 C 3 2 A. Proliferative phase Column I (Stages of menstrual cycle) B 4 3 B 2 1 4. Labia majora 159 Match the following columns. Codes A (a) 2 (c) 4 A (b) 1 (d) 3 Column I 158 Match the following columns. D. Production of ova C 3 1 162 Match the following columns. E 3 2 4 5 Column I B 1 2 B 3 1 2 3 C 1 2 3 2 D 2 3 4 1 164 Match the following columns. Column I Column II A. Hyaluronidase 1. Acrosomal reaction B. Corpus luteum 2. Morphogenetic movements C. Gastrulation 3. Progesterone D. Capacitation 4. Mammary gland E. Colostrum 5. Sperm activation Codes A (a) 5 (b) 1 (c) 3 (d) 1 B 2 3 2 2 C 4 2 5 3 D 1 5 4 4 E 3 4 1 5 www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 64 Codes A (a) 3 (b) 4 (c) 4 (d) 3 165 Match the following columns. Column I Column II A. Endometrium 1. Copulation site B. Menopause 2. Site of implantation C. Fallopian tube 3. Stopping of menstruation D. Vagina 4. Site of fertilisation Codes A (a) 2 (c) 1 B 3 4 C 4 3 D 1 2 (b) (d) A 1 4 B 2 3 C 1 2 2 2 D 2 1 3 4 167 Match the following columns. C 3 2 D 4 1 166 Match the following columns. Column I (Hormones) B 4 3 1 1 Column II (Functions) A. FSH 1. Prepares endometrium wall for implantation B. LH 2. Develops female secondary sexual characters C. Progesterone 3. Maturation of Graafian follicle D. Oestrogen 4. Maintenance of corpus luteum Column I NEET 2016 Column II A. Mons pubis 1. Embryo formation B. Antrum 2. Sperm C. Trophectoderm 3. Female external genitalia D. Nebenkern 4. Graafian follicle Codes A (a) 3 (b) 3 (c) 3 (d) 1 B 4 4 1 4 C 2 1 4 3 D 1 2 2 2 NCERT & NCERT Exemplar MULTIPLE CHOICE QUESTIONS NCERT 171 How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies? 168 Name the hormones involved in the regulation of spermatogenesis. (a) LH and FSH (c) Testosterone and LH (a) One (c) Six (b) Testosterone only (d) LH only 169 Read the following statements. I. Androgens are produced by Sertoli cells. II. Presence or absence of hymen is not a reliable indicator of virginity or sexual experience. III. Leydig cells synthesise androgens. IV. Oogenesis takes place in corpus luteum. Identify whether the given above statements are true or false. I (a) T (c) F II F T III F T IV T F (b) (d) I T F II F F III T T IV F T 170 How many eggs do you think would have been released by human ovary if the mother gave birth to identical twins? (a) (b) (c) (d) One, fertilised by two sperms Two, fertilised by different sperms One, fertilised by single sperm Two, fertilised by single sperm (b) Three (d) Indefinite NCERT Exemplar 172 Spot the odd one out from the following structures with reference to the male reproductive system. (a) (b) (c) (d) Rete testis Epididymis Vasa efferentia Isthmus 173 The vasa deferens receives duct from the seminal vesicle and opens into urethra as (a) (b) (c) (d) epididymis ejaculatory duct efferent ductule ureter 174 Urethral meatus refers to the (a) (b) (c) (d) urinogenital duct opening of vas deferens into urethra external opening of the urinogenital duct muscles surrounding the urinogenital duct www.mediit.in CHAPTER 03 > Human Reproduction 175 Seminal plasma, the fluid part of semen is contributed by I. seminal vesicle II. prostate gland III. urethra IV. bulbourethral gland (a) I and II (c) II, III and IV (b) I, II and IV (d) I and IV 176 Which one of the following is not a male accessory gland? (a) Seminal vesicle (c) Prostate (b) Mammary gland (d) Bulbourethral gland 177 Mature Graafian follicle is generally present in the ovary of a healthy human female around (a) (b) (c) (d) 5-8 days of menstrual cycle 11-17 days of menstrual cycle 18-23 days of menstrual cycle 24-28 days of menstrual cycle 178 Spermiation is the process of the release of sperms from (a) seminiferous tubules (c) epididymis (b) vas deferens (d) prostate gland 179 Acrosomal reaction of the sperm occurs due to (a) (b) (c) (d) its contact with zona pellucida of the ova reactions within the uterine environment of the female reactions within the epididymal environment of the male androgens produced in the uterus 180 Which of the following hormones is not secreted by human placenta? (a) hCG (c) Progesterone (b) Oestrogens (d) LH 181 Morula is a developmental stage (a) (b) (c) (d) between the zygote and blastocyst between the blastocyst and gastrula after the implantation between implantation and parturition 182 Match the following columns. Column I Column II A. Trophoblast 1. Embedding of blastocyst in the endometrium B. Cleavage 2. Group of cells that would differentiate as embryo C. Inner cell mass 3. Outer layer of blastocyst attached to the endometrium D. Implantation 4. Mitotic division of zygote Codes A (a) 2 (b) 3 (c) 3 (d) 2 B 1 4 1 4 C 3 2 2 3 D 4 1 4 1 65 183 Choose the incorrect statement from the following. (a) In birds and mammals, internal fertilisation takes place (b) Colostrum contains antibodies and nutrients (c) Polyspermy in mammals is prevented by the chemical changes on the egg surface (d) In the human female, implantation occurs almost seven days after fertilisation 184 Identify the correct statement from the following. (a) High levels of oestrogen triggers the ovulatory surge (b) Oogonial cells start to proliferate and give rise to functional ova in regular cycles from puberty onwards (c) Sperms released from seminiferous tubules are highly motile (d) Progesterone level is high during the post ovulatory phase of menstrual cycle 185 The spermatogonia undergo division to produce sperms by the process of spermatogenesis. Choose the correct one with reference to above. (a) Spermatogonia have 46 chromosomes and always undergo meiotic cell division (b) Primary spermatocytes divide by mitotic cell division (c) Secondary spermatocytes have 23 chromosomes and undergo second meiotic division (d) Spermatozoa are transformed into spermatids 186 Match between the following representing parts of the sperm and their functions and choose the correct option. Column I Column II A. Head 1. Enzymes B. Middle piece 2. Sperm motility C. Acrosome 3. Energy D. Tail 4. Genetic material Codes A (a) 2 (c) 4 B 4 1 C 1 2 D 3 3 (b) (d) A 4 2 B 3 1 C 1 3 D 2 4 187 Which among the following has 23 chromosomes? (a) Spermatogonia (c) Secondary oocyte (b) Zygote (d) Oogonia 188 The membranous cover of the ovum at ovulation is (a) (b) (c) (d) corona radiata zona radiata zona pellucida chorion 189 Identify the odd one from the following. (a) Labia minora (c) Infundibulum (b) Fimbriae (d) Isthmus www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 66 Answers Mastering NCERT with MCQs 1 (d) 2 (a) 3 (a) 4 (a) 5 (a) 6 (d) 7 (d) 8 (c) 9 (b) 10 (c) 11 (b) 12 (a) 13 (d) 14 (c) 15 (a) 16 (b) 17 (d) 18 (d) 19 (c) 20 (b) 21 (d) 22 (a) 23 (c) 24 (b) 25 (a) 26 (b) 27 (b) 28 (c) 29 (d) 30 (a) 31 (d) 32 (a) 33 (d) 34 (a) 35 (a) 36 (d) 37 (a) 38 (b) 39 (d) 40 (c) 41 (d) 42 (a) 43 (d) 44 (d) 45 (a) 46 (b) 47 (b) 48 (b) 49 (d) 50 (d) 51 (a) 52 (b) 53 (d) 54 (c) 55 (d) 56 (b) 57 (b) 58 (a) 59 (d) 60 (a) 61 (a) 62 (d) 63 (a) 64 (c) 65 (b) 66 (d) 67 (a) 68 (a) 69 (a) 70 (c) 71 (b) 72 (b) 73 (a) 74 (a) 75 (c) 76 (c) 77 (c) 78 (c) 79 (a) 80 (c) 81 (b) 82 (d) 83 (d) 84 (a) 85 (a) 86 (c) 87 (b) 88 (d) 89 (b) 90 (a) 91 (b) 92 (b) 93 (b) 94 (a) 95 (a) 96 (b) 97 (c) 98 (b) 99 (a) 100 (b) 101 (c) 102 (b) 103 (b) 104 (a) 105 (a) 106 (a) 107 (b) 108 (b) 109 (c) 110 (c) 111 (b) 112 (a) 113 (c) 114 (c) 115 (a) 116 (c) 117 (c) 118 (d) 119 (b) 120 (b) NEET Special Types Questions 121 (a) 122 (d) 123 (b) 124 (a) 125 (b) 126 (b) 127 (c) 128 (a) 129 (c) 130 (b) 131 (a) 132 (c) 133 (b) 134 (a) 135 (a) 136 (c) 137 (a) 138 (c) 139 (b) 140 (d) 141 (b) 142 (d) 143 (c) 144 (a) 145 (c) 146 (b) 147 (d) 148 (a) 149 (c) 150 (a) 151 (d) 152 (b) 153 (c) 154 (b) 155 (c) 156 (b) 157 (d) 158 (a) 159 (a) 160 (b) 161 (a) 162 (a) 163 (c) 164 (b) 165 (a) 166 (a) 167 (b) NCERT & NCERT Exemplar Questions 168 (a) 169 (c) 170 (c) 171 (c) 172 (d) 173 (b) 174 (c) 175 (b) 176 (b) 177 (b) 178 (a) 179 (a) 180 (d) 181 (a) 182 (b) 183 (b) 184 (d) 185 (c) 186 (b) 187 (c) 188 (a) 189 (a) Answers & Explanations 2 (a) The testes are suspended outside the abdominal 3 7 9 Answers & Explanations 10 cavity within a pouch called scrotum. Scrotum maintains the temperature of testes, i.e. 2-2.5°C below the body temperature, necessary for spermatogenesis. (a) Each human testis is oval in shape, with a length of about 4-5 cm and a width of about 2-3 cm. (d) Each seminiferous tubule is lined on its inside by two types of cells called male germ cells (spermatogonia) and Sertoli cells. (b) Spermatogonia or male germ cells undergo meiotic divisions finally leading to sperm formation. (c) Region outside the seminiferous tubules is called interstitial space, contains small blood vessels and interstitial cells or Leydig cells. 13 (d) Option (d) contains the incorrect pair. It can be corrected as Ejaculatory duct is formed by the union of vasa deferentia and duct of the seminal vesicle. Rest of the pairs are correct. 15 17 27 29 14 (c) Option (c) is the correct one. The correct information about the remaining incorrect option is as follows Each testis (A) possesses about 250 compartments called testicular lobules. Seminal vesicle (B) secretes mucous and a watery alkaline fluid rich in nutrients like fructose, citric acid, 32 inositol and prostaglandins. It provides energy to the spermatozoa. Prostate gland (D) releases an alkaline fluid that is rich in citrate ions, calcium phosphate and proteolytic enzymes to aid in sperm motility. (a) The shared terminal duct of the reproductive and urinary system in the human male is urethra. The urethra is about 8 inches (20 cm) long and opens at the end of the penis. The urethra provides an exit for urine from the bladder as well as for as semen from vasa efferentia during ejaculation. (d) The accessory glands found in males are paired seminal vesicles, the unpaired prostate gland and the paired bulbourethral glands. (b) Option (b) contains the incorrect pair. It can be corrected as Ampulla is the wider part of oviduct. Rest all the pairs are correct. (d) Option (d) contains the incorrect pair and can be corrected as Myometrium is the muscular layer of uterus which exhibits strong contractions during delivery. Endometrium is the glandular layer, which undergoes cyclic changes during menstrual cycle. Rest all the pairs are correct. (a) Several mammary ducts join to form a wider mammary ampulla which is connected to the lactiferous duct through which milk is sucked out. www.mediit.in 67 CHAPTER 03 > Human Reproduction 35 37 40 43 44 45 46 48 49 In the first group, Fallopian tube is the odd one out as it is a part of the female reproductive part. Rest are male reproductive parts. In the second series, ejaculatory duct is the odd one out as it is a part of the male reproductive tract. Rest are parts in females. In the third series, acrosome is the odd one out as it is a part of the sperm (male gamete). Rest are parts in female. In the fourth series, testis is odd one out as it is a primary male reproductive organ. Rest are accessory glands of male reproductive system. (a) Spermatogonium is diploid (2n) and contains 46 chromosomes. These multiply by mitotic division to form primary spermatocyte (2n). (a) Primary spermatocytes (2n) undergo meiosis-I to give rise to haploid secondary spermatocyes. The secondary spermatocytes undergo meiosis-II to produce spermatids which are then released as spermatids. (c) Secondary spermatocytes are the first cells in spermatogenesis in which the chromosome number becomes half. Thus, they contain haploid number of chromosomes. (d) The correct sequence of sperm formation is Spermatogonia → Spermatocyte → Spermatid → Spermatozoa. Spermatogonia are present on the inside wall of seminiferous tubule which undergoes mitotic division and increase their number. Primary spermatocytes are some of the spermatogonia, which periodically undergo meiosis and form secondary spermatocytes. These undergo the second meiotic division to produce four, equal haploid spermatids. The spermatids are further transformed into spermatozoa (sperm) and are finally released. (d) Spermiogenesis is the process of transformation of spermatids (n) into spermatozoa (n) or sperms. It involves the differentiation phase in which one spermatid develops into one spermatozoon. Spermiation involves the release of sperms from seminiferous tubules through Sertoli cells. (a) Spermatogenesis is initiated at puberty due to the increase in Gonadotropin Releasing Hormone (GnRH) by hypothalamus. (b) GnRH is a hypothalamic hormone. It stimulates the anterior lobe of pituitary gland to secrete LH and FSH. (b) Sperms of mammals depend for movement on tail and middle piece. The middle piece possesses numerous mitochondria, which produce energy for the movement of tail that facilitates sperm motility essential for fertilisation. (d) The middle piece of the sperm utilises fructose as a source of energy. It is packed with numerous mitochondria which utilise fructose as a source of energy to provide motility to sperm to reach out ovum (egg cell). 50 (d) Option (d) contains the incorrect match. It can be 51 53 57 58 60 63 64 67 68 corrected as The combined secretion of three glands namely, seminal vesicles, prostate gland, Cowper’s gland, together with sperms collectively form semen. Rest of the matches are correct. (a) Option (a) contains the incorrect match. It can be corrected as Antrum is the fluid-filled cavity which is found in tertiary follicle or Graafian follicle. Rest of the matches are correct. (d) The zona pellucida in an antral follicle is acellular. It is a glycoprotein layer surrounding the plasma membrane of the mammalian oocytes. (b) Option (b) is correct. In the first series, polar body is the odd one out as it is a structure formed through oogenesis in females. Rest are structure of spermatogenesis. In the second series, acrosome is the odd one out as it is a part of the sperm or the male gamete. Rest are parts in females. In the third series, Fallopian tube is the odd one out as it is a part of the female reproductive system. Rest are structure in males. In the fourth series, testes is the odd one out as it is the primary sex organ of the male reproductive system. Rest are accessory glands of male reproductive system. (a) The rhythmic series of changes that occurs in the reproductive organs of female primates like monkeys, apes and human beings, is called menstrual cycle. It is repeated at an average interval of about 28/29 days. (a) Menstrual flow occurs due to the lack of progesterone. Progesterone is secreted by corpus luteum and is essential for the maintenance of endometrium. In the absence of progesterone, the endometrium starts to degenerate. This leads to menstrual flow in which the endometrial wall gets shed off. (a) During the follicular phase of menstrual cycle, the endometrium of the uterus regenerates through proliferation. (c) The level of LH is maximum at the time of ovulation (i.e. ovulatory phase) in the menstrual cycle. It is called as LH surge. It induces rupture of Graafian follicles and thereby the release of ovum, i.e. ovulation. (a) Decrease in oestradiol is not associated with ovulation in human females. Oestradiol is also known as oestrogen which is a primary female sex hormone. During the ovulation in human females, level of oestradiol increases. Its main function is to mature and maintain the reproductive tract. (a) No new follicles develop in the luteal phase of menstrual cycle because after ovulation follicles do not remain in the ovary. It is because during this phase, Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) levels decrease. Instead, the already ruptured follicle closes after releasing the egg and forms Answers & Explanations 33 (d) Option (d) is correct. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 68 69 70 71 74 79 Answers & Explanations 81 83 84 87 a corpus luteum during luteal phase, which produces progesterone. (a) The formation of corpus luteum is induced by LH (Luteinizing Hormone). LH causes ovulation and stimulates the remaining cells of the ovarian follicle to develop corpus luteum. (c) Corpus luteum is a temporary endocrine gland in the human body. It secretes small amount of oestradiol and significant amount of progesterone hormone. In the absence of fertilisation, the corpus luteum degenerates. (b) The main function of mammalian corpus luteum is the secretion of progesterone, which is essential for the maintenance of endometrium. (a) Option (a) shows incorrect match. It can be corrected as Regeneration of endometrium under the influence of oestrogen and maturation of Graafian follicle occurs during the proliferative phase. Rest of the options are correct matches. (a) Option (a) depicts the correct levels of LH, FSH and progesterone. On the 13-14 days (Proliferative phase) FSH and LH have high concentration, whereas progesterone has low concentration. On the 20-28 days (Luteal phase), FSH and LH have low concentration, whereas progesterone has high concentration. (b) The option depicting the correct sequence events occurring in the female reproductive cycle is I → III → V → IV → II. In human female reproductive cycle or menstrual cycle, during proliferative phase, the anterior lobe of pituitary gland secretes the Follicle Stimulating Hormone (FSH), which stimulates ovarian follicle to secrete oestrogen. During the second week of reproductive cycle, most of the developing follicle die and usually one follicle continues to mature. Also, the Luteinizing Hormone (LH) in blood level increases and a small surge of FSH occurs. Ovulation takes place, which releases immature egg into abdominal cavity. During ovulation, the follicle breaks upon and collapses under the continuous influence of Luteinizing Hormone (LH). It begins to enlarge and forms a yellowish structure called corpus luteum or yellow body. (d) Capacitation is the process, where the spermatozoa acquire the capacity to fertilise the eggs. It occurs in female reproductive tract. (a) Fertilisation in human, is practically feasible only if the ovum and sperms are transported simultaneously at the ampullary-isthmic junction of Fallopian tube. This is the reason why every copulation does not lead to fertilisation and pregnancy. (b) Acrosomal reaction is the digestion of the zona pellucida. It involves the progressive fusion of the acrosomal membrane with the plasma membrane of the sperm. It creates pores through which the acrosomal enzymes can be released by exocytosis. 88 90 91 101 104 These enzymes include a protein digesting enzyme, corona penetrating enzyme, zona lysin (acrosin) and hyaluronidase. These enzymes allow the sperm to digest and create a path through the zona pellucida to the oocyte. (d) Extrusion of second polar body from egg nucleus occurs after the entry of sperm but before fertilisation. The entry of sperm into female egg causes the breakdown of Metaphase Promoting Factor (MPF) and turns on Anaphase Promoting Factor (APF). Hence, the secondary oocyte completes its meiotic division after fertilisation and is said to be activated. (a) The sex of the foetus will be decided at fertilisation by male gamete. The chromosome pattern in the human female is XX and in the male is XY. If the sperm carrying X-chromosome fertilises the ovum, the zygote would develop into a female and if Y fertilises the ovum, the zygote would be a male. Thus, the sex of the foetus depends on the type of chromosome present in male gamete which fertilises the egg. (b) Zygote divides rapidly by mitotic division when it moves through the isthmus of the oviduct towards the uterus. This rapid division is called cleavage. (c) Chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between the developing embryo and the maternal body. This structure is called placenta. (a) Placenta acts as endocrine tissue and secretes the following hormones to maintain pregnancy l l l human Chorionic Gonadotropin (hCG) It stimulates and maintains the corpus luteum to secrete progesterone until the end of pregnancy. human Placental Lactogen (hPL) It is also known Human Chorionic Somatomammotropin (HCS), it stimulates the growth of mammary glands during pregnancy. Progesterone and oestrogen support foetal growth, maintain pregnancy, inhibit uterine contractions, etc. 106 (a) Chorion serves as the structure analogous to placenta in mammals. It completely encloses the developing embryo and extraembryonic tissues like placenta, it is also highly specialised to facilitate the transfer of nutrients, gases and wastes between the embryo and mother’s body. This is accomplished by chorionic villi that emerge from the chorion and invade the endometrium. 107 (b) Relaxin is secreted by the ovaries in the later phase of pregnancy. Relaxin increases the flexibility of the pubic symphysis and ligaments of the sacroiliac and sacrococcygeal joints that help to dilate the cervix during labour. 109 (c) Option (c) depicts the correctly matched pairs. Rest of the incorrect pairs can be corrected as l l Mesoderm gives rise to dermis. Ectoderm gives rise to enamel of teeth. www.mediit.in 69 CHAPTER 03 > Human Reproduction 111 112 113 115 ectoderm and mesoderm. It is one of the extraembryonic membrane which is formed by the amniogenic cells of ectodermal origin on the inner side and somatopleuric extraembryonic mesoderm on the outer side. This membrane acts as a shock absorber for the foetus, regulates foetal body temperature and prevents desiccation. (b) Gastrulation is a process by which blastocyst transforms into the three layered (germ layers) structure called gastrula. The three germ layers are inner endoderm, middle mesoderm and outermost ectoderm. These give rise to all the tissues and organs of the developing foetus. (a) The correct sequence of embryonic development is Zygote → Cleavage → Morula → Blastula → Gastrula. Fertilisation of the haploid egg by a haploid sperm gives rise to a diploid zygote. At about 30-36 hrs after fertilisation, the zygote divides into smaller cells by a process called cleavage. It is division of cells. It results in a solid ball of cells, called morula. It is a 16-celled stage. It forms blastula which is a 64-celled stage. It contains a fluid-filled cavity called blastocoel. It ultimately leads to the formation of multilayered gastrula. (c) Option (c) contains the incorrect pair. It can be corrected as By the end of 12 weeks (first trimester), most of the major organ systems like the limbs and external genital organs are well-developed. Rest of the options are correct pairs. (a) The process of delivery of the foetus (childbirth) is called parturition which is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and also from the placenta which induce mild uterine contractions called foetal-ejection reflex. 121 (a) Both Assertion and Reason are true and Reason is 122 123 124 125 126 127 117 (c) Oxytocin hormone is responsible for both the milk ejection reflex and foetal-ejection reflex. It is a peptide hormone normally produced in the hypothalamus and released by the posterior pituitary gland. 118 (d) Option (d) is not correct function of placenta. Pituitary secretes oxytocin during parturition. It is not a function of the placenta. The functions of placenta are to supply oxygen and nutrients to embryo, secrete oestrogen, facilitate removal of carbon dioxide and waste materials from embryo. 120 (b) Colostrum is the milk produced during the initial few days of lactation. It contains several essential antibodies, which are absolutely essential to develop resistance against pathogenicity in newborn. So, it is recommended by doctors to feed newborn from breast milk during the initial period of infant growth. 128 129 the correct explanation of Assertion. The testes are situated outside the abdominal cavity within a pouch called scrotum. The scrotum helps in maintaining the low temperature of the testes (2-2.5°C) lower than the normal internal body temperature necessary for spermatogenesis. (d) Assertion is false, but Reason is true. Assertion can be corrected as In the testis, spermatogenesis occurs in the seminiferous tubules and testosterone secretion takes place in interstitial cells. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Seminiferous tubule is lined on its inside by two types of cells called male germ cells and Sertoli cells. The male germ cells form sperm and Sertoli cells provide nutrition to the germ cells. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The bulbourethral gland is a male accessory gland. Its secretions help in lubricating the penis to facilitate reproduction. (b) Both Assertion and Reason true, but Reason is not the correct explanation of Assertion. The correct explanation would be Fimbrae are finger-like projections of infundibulum of the oviduct which is closest to the ovary. Fimbrae collect the released from ovary and move it down into the Fallopian tube. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The act of giving birth to a baby is called parturition. It is induced by a complex neuroendocrine mechanism. The signals originate from a fully developed foetus and the placenta, which induces mild uterine contractions. (c) Assertion is true, but Reason is false and it can be corrected as It is the sperm, which needs energy to move about in female reproductive tract in search of ova so that fertilisation can take place. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Menstrual phase is the phase of menstrual flow/menses which continues for 3-5 days and involves discharge of blood (a total of 50-100 mL) along with shedding off endometrial lining (uterus, Fallopian tube and vagina) due to reduced levels of both oestrogen and progesterone hormones. As such menstrual phase is also called funeral of unfertilised egg or shedding tears of lost ovum. (c) Assertion is true, but Reason is false. It can be corrected as In menstrual cycle, rapid secretion of LH leads to its maximum level during mid-cycle. It is called LH surge. It induces rupture of Graafian follicle, thereby releasing ovum (ovulation). Answers & Explanations 110 (c) Amnion of mammalian embryo is derived from www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 70 130 (b) Both Assertion and Reason are true, but Reason is not 131 132 133 135 136 the correct explanation of Assertion. Large amount of progesterone is essential for the maintenance of the endometrium, to which fertilised ovum gets attached (implantation). (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. All copulations do not lead to fertilisation as the synchronisation of sperm and ova reaching the ampullary-isthmic junction of the Fallopian tube is important. (c) Assertion is true, Reason is false. It can be corrected as In human, the gametes contributed by the male determines the sex of the child. Thus, sex in human is a polygenic trait depending upon a cumulative effect of some genes present on Y-chromosome and not on X-chromosome. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Placenta acts as an endocrine tissue and produces several hormones like hCG, hPL, oestrogens, progestogens, etc., which are essential for pregnancy. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Colostrum is the milk produced during the initial few days of lactation. It is rich in antibodies essential to render immunity for newborn babies. So, breastfeeding is highly recommended during the initial period of infant growth. (c) The statement in option (c) is correct. Rest of the statements are incorrect and can be corrected as l l l Size of testis is 4-5 cm in length and 2-3 cm in width. The scrotum is maintained at a temperature 2-2.5°C lower than normal body temperature. The earliest stages of spermatogenesis occur within the testis. 141 (b) Statement I is incorrect and can be corrected as 143 144 145 146 149 Each testis has about 250 compartments called testicular lobules. Rest of the statements are correct. (c) Statement in option (c) represents the false statement for uterus. It can be corrected as It opens into vagina through a narrow cervix. The cavity of the cervix is called cervical canal. Rest of the statements are correct for uterus. (a) Statement in option (a) is incorrect and can be corrected as Viability of a sperm means the capability of a sperm, fertilising an egg. Sperms are viable for 24 hrs-48 hrs, whereas the ovum is viable for only 24 hrs. Rest of the statements are correct. (c) Statement in option (c) represents the incorrect statement for oogonia and can be corrected as Formation of millions of oogonia is initiated during the embryonic development stage within each foetal ovary, no more oogonia are formed and added after birth. Rest of the statements are correct. (b) Statement in option (b) represents the incorrect statement. It can be corrected as The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase and stimulates follicular development as well as secretions of oestrogens by growing follicles. Rest of the statements are correct (c) Statement in option (c) is correct. Rest of the statements are incorrect and can be corrected as l l Answers & Explanations 137 (a) The statement in option (a) is incorrect and can be corrected as Oogonia are formed in the female at the foetal stage and no more oogonia are formed and added after birth. Rest of the statements are correct. 138 (c) The statement in option (c) is incorrect and can be corrected as Ovaries produce several steroid hormones and the female gamete (ovum). 139 (b) The statements II, III and IV are correct. Statements I and V are incorrect and can be corrected as l l The uterus is single and is also called womb. Perimetrium of uterus is external and thin, myometrium is the middle thick layer of smooth muscles and endometrium is the inner glandular layer. 150 (a) The statements I and III are true, but II is false. Statement II can be corrected as Vas deferens joins a duct from seminal vesicle to form ejaculatory duct. 152 (b) Statements II and IV are correct. Statements I and III are incorrect and can be corrected as l l Cleavage divisions bring about considerable decrease in the mass of protoplasm. Blastomeres arrange themselves to form inner cell mass and trophoblast. 155 (c) Only statement I is correct regarding male pronucleus. Others statements are incorrect and can be corrected as l 140 (d) Statements II, III, IV and V are correct. l Statement I is incorrect and can be corrected as Spermatogonia are diploid and spermatids are haploid. High levels of FSH and LH stimulates ovulation (not the thickening of endometrium or implantation of the embryo). High levels of oestrogen stimulates the thickening of the endometrium. l Only the head of the sperm contributes towards pronucleus formation. Male pronucleus lacks mitochondria. Sperm head contains pronucleus having haploid set of chromosomes. www.mediit.in 71 CHAPTER 03 > Human Reproduction corrected as D–Ovary produces oestrogen required for the development of secondary sexual characters in females. Rest of the statements are correct. 168 (a) LH and FSH regulate the process of spermatogenesis. FSH acts on Sertoli cells whereas LH acts on Leydig cells. 169 (c) Statements II and III and true. Statements I and IV are false and can be corrected as l l Androgens are produced by Leydig’s cells. Oogenesis takes place in the ovary. 170 (c) Identical twins are produced from a single egg 171 172 173 174 175 176 177 179 (fertilised by single sperm) by the separation of early blastomeres resulting from first zygotic cleavage. They have same the genetic makeup. (c) Dogs and rodents are polyovulatory species. In these animals, more than one ovum is released from ovary at the time of ovulation. Hence, six eggs were released by the ovary of a female dog produce six puppies. (d) Isthmus is the odd one out of the given options as it is a part of the Fallopian tube (of the female reproductive system). Rest of the options, i.e. rete testis, epididymis and vasa efferentia are a part of the male reproductive system. (b) The vas deferens joins a duct from the seminal vesicle and opens into the urethra as the ejaculatory duct. These ducts store and transport the sperms. (c) The urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus. In other words, it is the external opening of the urinogenital duct. (b) Seminal vesicles, prostate and the bulbourethral glands are the male accessory glands whose secretions constitute the seminal plasma (semen). Urethra does not secrete semen. The transport of sperms from the testis to the outside occurs through urethra. (b) Mammary gland is a part of female reproductive system. Rest are the male accessory glands. (b) In humans, the menstrual cycle lasts for about 28/29 days. During 11–17 days of the menstrual cycle a mature Graafian follicle is seen in healthy human female. (a) Binding of the sperm head to a receptor molecule on the zona pellucida layer of the ova induces the acrosome of the sperm to release its hydrolytic enzymes. 180 (d) Placenta acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin, oestrogen, progesterone, etc. LH is produced by the anterior lobe of the pituitary gland. 181 (a) The embryo with 8-16 blastomeres is called a morula. It is an embryonic developmental stage between the zygote and the blastocyst. 183 (b) Statement in option (b) is incorrect and can be corrected as Colostrum contains several antibodies which are absoutely essential to develop immunity in newborns. Rest of the statements are correct. 184 (d) Option (d) represents the correct statement. Other statements are incorrect and can be corrected as l l l Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge. Oogenesis is initiated during the early embryonal stage when million of gamete mother cells (oogonia) are formed within each foetal ovary, no more oogonia are formed and added after birth. Sperms released from epididymis are highly motile. 185 (c) Option (c) contains the correct statement. Rest of the statements are incorrect and can be corrected as l l l Spermatogonia are diploid cells present on the inside wall of seminiferous tubules that multiply by mitotic divisions. Primary spermatocyte undergo meiosis-I to give rise to secondary spermatocytes (haploid). Each secondary spermatocyte has 23 chromosomes and undergoes meiosis-II to gives rise to two haploid spermatids which are transferred to spermatozoa by spermiogensis. 188 (a) The outermost membranous cover of the ovum at ovulation is corona radiata. It is formed by follicular cells. Inner to corona radiata is zona pellucida, which is made up of three different glycoproteins secreted by the ovum itself. 189 (a) Labia minora are paired folds of tissues under labia majora which in turn surrounds the vaginal opening. It is a part of the external genitalia of the female reproductive system. Fimbriae, infundibulum and isthmus along with ampulla are parts of oviduct (Fallopian tube). Answers & Explanations 156 (b) Statement I is the only incorrect statement. It can be www.mediit.in CHAPTER > 04 Reproductive Health NEET Å Å KEY NOTES According to World Health Organisation (WHO), reproductive health means total well-being in all aspects of reproduction, i.e. physical, emotional, behavioural and social. Therefore, a society with people having physically and funtionally normal reproductive organs and normal emotional and behavioural interactions among them in all sex related aspects might be called reproductively healthy. Reproductive Health–Problems and Strategies Å Å Å Å Å India initiated many action plans and programmes like ‘family planning’ (1951) at national level to attain total reproductive health. Currently, Reproductive and Child Healthcare (RCH) programmes are under operation. RCH is an initiative to create awareness among the people about reproduction related aspects and providing facilities and support for building up a reproductive healthy society. Introduction of sex education in schools is also being encouraged to provide right information to the young, so as to discourage children from believes in myths and misconception about sex-related aspects. Proper information about reproductive organs, adolescence and related changes, safe and hygienic sexual practices and Sexually Transmitted Diseases (STDs), it would help people to lead a reproductively healthy life. Successful implementation of various action plans have improved reproductive health as indicated by better awareness about sex related matters, increased number of medically assisted deliveries, better detection and cure of STDs, statutory ban on amniocentesis and overall increased medical facilities for all reproduction related problems. Amniocentesis It is a technique used to find out genetic disorders such as Down‘s syndrome, haemophilia, etc., in developing foetus by using amniotic fluid. It is also misused to check foetal sex. Sex-determination is based on the chromosomal pattern in the amniotic fluid surrounding the developing foetus. A statutory ban has been implemented on this technique for sex-determination to legally check increasing menace of female foeticides. Å Å Å Population Stabilisation and Birth Control Å Increased health facilities, rapid decline in death rate, Maternal Mortality Rate (MMR) and Infant Mortality Rate (IMR) as well as an increase in number of people in reproducible age and better living conditions had an explosive impact on the growth of population. This population explosion could lead to the scarcity of even basic requirements like food, shelter, etc. Å The population growth can be controlled by motivating small families, by using various contraceptive methods. Statutory raising of marriageable age of the female to 18 years and male to 21 years and incentives given to couples with small families are two other methods to tackle population growth. An ideal contraceptive should be user-friendly, easily available, effective, reversible with no or least side effects. It should also in no way interfere with sexual desire and sexual act of the user. Contraceptive methods could be divided into following categories Å 1. Natural Methods Å It works on the principle of avoiding chances of ovum and sperm meeting. It includes Periodic abstinence in which couples avoid coitus from day 10 to 17 of menstrual cycle, as chances of fertilisation are very high during this period. n www.mediit.in 73 CHAPTER 04 > Reproductive Health n n Withdrawal or Coitus interruptus in which male partner withdraws penis from vagina just before ejaculation to avoid insemination. 6. Surgical Methods Å Lactational amenorrhea method includes the absence of menstruation after parturition and due to intense lactation and no ovulation in this period, chances of fertilisation is nil. It is also called sterilisation. These are used as terminal method of contraception in male and female to prevent any more pregnancy by blocking gamete transport. These include n 2. Barrier Methods Å In this, ovum and sperms are prevented from physical meeting with the help of barriers. These include n n Å Vasectomy is the surgical method in male, a small part of the vas deferens is removed or tied up through a small incision on the scrotum to prevent release of sperms. Condoms are barriers made up of rubber or latex sheath, used to cover the penis in the male or vagina and cervix in the female. They also prevent from STDs. Vas deferens tied and cut Diaphragms, cervical caps and vaults are barriers made of rubber that are inserted into the female reproductive tract to cover the cervix during coitus. Spermicidal creams, jellies and foams are usually used along with these to increase their contraceptive efficiency. These help to kill the sperms. Vasectomy 3. Intra Uterine Devices (IUDs) Å Å n These are inserted by doctor or trained nurses into the female uterus through vagina. IUDs may be non-medicated (e.g. Lippes loop), copper releasing (Cu-T, Cu-7, Multiload-375) and the hormone releasing (Progestasert, LNG-20). Tubectomy is the surgical method in females in which small part of Fallopian tube is removed surgically. These techniques are highly effective but poorly reversible. Fallopian tubes tied and cut These IUDs increase phagocytosis of sperms within the uterus, suppress the fertilising capacity and motility of sperms and make the uterus unsuitable for implantation and the cervix hostile to the sperms. 4. Oral Pills Å These are progesterone or progesterone-oestrogen combination used by females in the form of tablets and hence popularly called the pills. Å They inhibit ovulation and implantation as well as change the quality of cervical mucus to prevent/retard entry of sperms. For example, Saheli, developed by scientists at Central Drug Research Institute (CDRI) Lucknow, India, is once a week pill with non-steroidal preparation. Å Administration of pills within 72 hours of coitus is found to be very effective as emergency contraceptives. 5. Injectable and Implants Å These are the methods in which progesterone alone or in combination with oestrogen can be used by females under the skin. Å Such injectables and implants are functionally similar to pills and their effective period is much longer. Tubectomy Medical Termination of Pregnancy (MTP) Å An intentional or voluntary termination of pregnancy before full term or before the foetus becomes viable is called Medical Termination of Pregnancy (MTP) or induced abortion. Å Nearly 45 to 50 million, MTPs are performed in a year all over the world which accounts to 1/5th of the total number of conceived pregnancies in a year. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 74 Å Government of India legalised MTP in 1971 with some strict conditions to avoid its misuse, especially to check indiscriminate and illegal female foeticides, which are reported to be high in India. Å The late detection leads to complications like Pelvic Inflammatory Diseases (PIDs), abortions, still births, ectopic pregnancies, infertility or even cancer of the reproductive tract. Å The Medical Termination of Pregnancy (Amendment) Act, 2017 was enacted by the government of India with the intension of reducing the incidence of illegal abortion and consequent maternal mortality and morbidity. Å One should not panic because prevention from STIs is possible and one could be free of these infections, by following these simple principles as given below Å According to this Act, a pregnancy may be terminated on certain considered grounds within the first 12 weeks of pregnancy on the opinion of one registered medical practitioner. If the pragnancy has lasted more than 12 weeks, but fewer than 24 weeks, two registered medical practitioners must be of the opinion, formed in good faith, that the required ground exist. Å The grounds for such termination of pregnancies are n n The continuation of the pregnancy would involve a risk to the life of the pregnant woman or of grave injury physical or mental health. There is a substantial risk that of the child were born, it would suffer from such physical or mental abnormalities as to be seriously handicapped. Sexually Transmitted Infections (STIs) Å Å Å Diseases which are transmitted through sexual intercourse are called Sexually Transmitted Infections (STIs) or Veneral Diseases (VDs) or Reproductive Tract Infections (RTIs). Genital herpes, syphilis, gonorrhoea, chlamydiasis, genital warts, hepatitis-B and AIDS (caused by HIV) are some common STIs. STIs like hepatitis-B and HIV can also be transmitted by the following Sharing of contaminated injection needles, surgical instruments, etc., with infected persons. Transfusion of blood. From infected mother to foetus. n n n Å Å Å Å Except for hepatitis-B, genital herpes and HIV infections, all other diseases are completely curable, if detected early and treated properly. The early symptoms of STIs are minor and include itching, fluid discharge, slight pain, swellings, etc., in the genital region. Infected females may often be asymptomatic and hence may remain undetected for long. The patients remain undetected due to the following reasons The absence or less significant symptoms in early stages of infection. Social stigma attached to the STIs. n n NEET (i) Avoid sex with unknown/multiple partners. (ii) Always use condoms during coitus. (iii) In case of doubt, consult a doctor as early as possible for early detection and get completely treated if diagnosed with disease. Infertility Å Couples who are not able to produce children inspite of unprotected sex are considered infertile. The reason for this could be many physical, congenital, diseases, drugs or even psychological. Å Various methods are now available to help such couples. These techniques are together called Assisted Reproductive Technologies (ARTs). Å In Vitro Fertilisation (IVF) is the fertilisation outside the body followed by embryo transfer, which is commonly called test tube baby programme. n Å The zygote or early embryo (upto 8 blastomeres) could be transferred into Fallopian tube called ZIFT (Zygote Intra Fallopian Transfer) and embryo with more than 8 blastomeres into the uterus called IUT (Intra Uterine Transfer) to complete its further development. Embryos formed by in vivo fertilisation (fertilisation within the female body) also could be used for such transfer to assist those females who cannot conceive. GIFT (Gamete Intra Fallopian Transfer) is the transfer of gametes collected from a donor into Fallopian tube of another female who do not produce ovum. ICSI (Intra Cytoplasmic Sperm Injection) is specialised procedure to form an embryo in laboratory in which sperm is directly injected into the ovum. n n n Artificial Insemination (AI) used in the infertility cases in which male partner is unable to inseminate the female or have a very low sperm counts (azospermia) in the ejaculates. In this technique, semen collected from donor is artificially introduced into the vagina or uterus of the female by IUI (Intra Uterine Insemination). KEY NOTES www.mediit.in CHAPTER 04 > Reproductive Health 75 Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Reproductive Health–Problems and Strategies 1 Reproductive health is the well-being of (a) (b) (c) (d) 2 Family planning programme was initiated in (a) 1951 (b) 1920 (c) 1930 (d) 1950 3 What is the full form of RCH? (a) (b) (c) (d) 5 Amniocentesis is the detection of (a) (b) (c) (d) physical aspects emotional and behavioural aspects social aspects All of the above Reproductive and Child Healthcare Reproduction, Contraception and Health Reproduction and Child Health None of the above 4 What are the various ways through which the reproductive health can be improved? I. Education II. Awareness III. Encouraging myths IV. Ban on amniocentesis (a) I and II (b) II and III (c) III and IV (d) I, II and IV chromosomal pattern by taking amniotic fluid chorionic fluid from developing embryo chromosomal pattern after childbirth chromosomal pattern before fertilisation 6 Which of the following cannot be detected in a developing foetus by amniocentesis? NEET 2013 (a) Klinefelter’s syndrome (b) Sex of the foetus (c) Down’s syndrome (d) Jaundice 7 Indicators of improved reproductive health of the society are (a) (b) (c) (d) better detection and cure of STDs improved medical facilities decreased maternal and infant mortality rates All of the above TOPIC 2 ~ Population Stabilisation and Birth Control 13 Natural methods of contraception are the natural 8 Population explosion is (a) (b) (c) (d) increased frequency of diseases in population rapid increase in population number rapid decrease in population number None of the above 9 India’s population cross 1 billion in (a) May 2001 (c) May 2000 (b) Dec 1999 (d) Dec 1991 10 Causes for increased population growth in India is/are (a) (b) (c) (d) increase in birth rate decrease in maternal mortality rate lack of education All of the above 11 Which of the following are the consequences of over population? (a) (b) (c) (d) It increases the poverty of a country It leads to shortage of food supply It results in unemployment All of the above 12 An ideal contraceptive should be (a) user friendly (c) Both (a) and (b) (b) reversible (d) decrease sexual drive ways to (a) (b) (c) (d) increase spermicidal activity prevent fertilisation decrease mortality increase mortality 14 One of the legal method of birth control is NEET 2013 (a) abortion by taking an appropriate medicine (b) by abstaining from coitus from day 10-17 of the menstrual cycle (c) by having coitus at the time of day break (d) by a premature ejaculation during coitus 15 Periodic abstinence is avoiding sex during (a) (b) (c) (d) follicular phase ovulatory phase menstrual phase None of the above 16 The lifespan of a sperm in female body is (a) 1-2 days (c) 4 days (b) 3 days (d) Only 1 day www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 76 17 Coitus interruptus is the withdrawl method of natural 29 …A… makes the uterus unsuitable for implantation contraception involving and the cervix hostile to …B… . (a) (b) (c) (d) (a) (b) (c) (d) withdrawl of penis from vagina before ejaculation withdrawl of penis from vagina after ejaculation sex during ovulation no sex during ovulation 18 Lactational amenorrhea is the (a) (b) (c) (d) 30 The females wanting to delay pregnancy or space absence of menses in adult age absence of menses in elderly age absence of menses during lactation no menses during pregnancy children should use (a) Femidoms (c) Tubectomy (a) progesterone (c) Both (a) and (b) rubber/latex sheath which is used to cover (b) cervix in female (d) None of these (b) for female use only (d) None of these 21 Spermicidal creams are used in addition to condoms, diaphragms, cervical cap and vaults for (a) (b) (c) (d) (a) (b) (c) (d) (b) Cu-7 (d) Lippes loop NEET 2019 35 Implants (the progesterone or progesterone-oestrogen (b) Cu-7 (d) All of these combination) are used by the females usually under the 25 An injectible form of the hormone based (a) (b) (c) (d) contraceptive is (b) Depo-provera (d) Saheli 26 Select the hormone releasing intrauterine devices. (a) Multiload-375, Progestasert (b) Progestasert, LNG-20 (c) Lippes loop, Multiload-375 (d) Vaults, LNG-20 A–ovulation, B–cervical mucus A–oogenesis, B–structure A–oogenesis, B–nucleus A–spermatogenesis, B–cervical mucus (a) is an IUD (b) increases the concentration of oestrogen and prevents ovulation in females (c) blocks oestrogen receptors in the uterus preventing eggs from getting implanted (d) is a post-coital contraceptive 24 Example of copper releasing IUD is/are (a) Norplant (c) Mala-D (b) A–21, B–7 (d) A–24, B–4 34 The contraceptive ‘Saheli’ 23 Example of the non-medicated IUD is (a) Cu-T (c) Multiload-375 (a) A–27, B–1 (c) A–22, B–5 well as quality of …B… to prevent the entry of sperms. Inter Uterine Devices Intra Uterine Devices Inter Uterine Development Intra Uterine Development (a) Cu-T (c) Multiload-375 starting preferably within first five days of menstrual cycle. After a gap of …B… days, it has to be repeated in the same pattern. 33 Oral contraceptives inhibit …A… and implantation as lubrication killing germs increasing contraceptive effectiveness None of the above 22 IUDs stands for (a) (b) (c) (d) (b) oestrogen (d) None of these 32 Pills have to be taken daily for period of …A… days 20 Diaphragms, cervical caps and vaults are (a) non-usable (c) for male use only (b) IUDs (d) Vaults and caps 31 Oral contraceptives have hormonal preparation of 19 Condoms or Femidoms are made up of thin (a) penis in male (c) Both (a) and (b) A–Hormone releasing IUD; B–spermatogonia A–Hormone releasing IUD; B–sperms A–Sperms; B–hormonal releasing IUD A–Sperms; B–ova NEET 2019 skin of the inner arm above elbow vagina upper skin of stomach cervix 36 Choose the correct option from A, B and C. 27 Copper releasing IUDs are used for suppressing the (a) activity of ova (b) activity of the uterus (c) motility of the sperms (d) motility of ova 28 Lippes loop prevent contraception by (a) preventing ovulation (b) phagocytosis of sperms (c) suppressing sperm motility (d) All of these A (a) (b) (c) (d) B C A–Condoms, B–Copper-T, C–Implants A–Tubectomy, B–Implants, C–Copper-T A–Vasectomy, B–Condoms, C–Copper-T A–Copper-T, B–Condoms, C–Implants www.mediit.in CHAPTER 04 > Reproductive Health 77 37 Administration of progesterone, progesterone- oestrogen combination or IUDs are effective within …… hours of coitus. (a) 72 (b) 48 (c) 24 (d) 96 42 Which of the following approaches does not give the defined action of contraceptive? (a) Intra uterine devices Increase phagocytosis of sperms, suppress sperm motility and fertilising capacity of sperms (b) Hormonal contraceptives Prevent/ retard entry of sperms, prevent ovulation and fertilisation 38 What is the difference in oral contraceptives and hormonal implants? (a) (b) (c) (d) They differ in their sites of implantation They differ in their duration of action Both (a) and (b) None of the above (c) Vasectomy Prevents spermatogenesis (d) Barrier methods Prevent fertilisation 43 What is the figure given below showing in particular? 39 Which of the following contraceptive methods do involve a role of hormone? (a) (b) (c) (d) NEET 2016 CBSE-AIPMT 2012 NEET 2019 Barrier method, lactational amenorrhea, pills Cu-T, pills, emergency contraceptives Pills, emergency contraceptives, barrier methods Lactational amenorrhea, pills, emergency contraceptives 40 Tubectomy is a method of sterilisation in which CBSE-AIPMT 2014 (a) small part of the Fallopian tube is removed or tied up (b) ovaries are removed surgically (c) small part of vas deferens is removed or tied up (d) uterus is removed surgically 41 Name the part cut and tied in male sterilisation. Also, (a) Ovarian cancer (b) Uterine cancer (c) Tubectomy (d) Vasectomy 44 Which of the following birth control measure can be name the procedure. considered as the most effective and reliable? (a) (b) (c) (d) (a) (b) (c) (d) Vas deferens, tubectomy Vas deferens, vasectomy Vasa efferentia, tubectomy Vasa efferentia, vasectomy The rhythm method Use of physical barriers Intra uterine devices Sterilisation techniques TOPIC 3 ~ Medical Termination of Pregnancy and Sexually Transmitted Infections 45 MTP stands for (a) (b) (c) (d) Medical Termination of Pregnancy Mental Trauma Phase Menstrual Trauma Pain Menstrual Temporary Pain 46 MTP helps to overcome pregnancy that result due to (a) (b) (c) (d) rapes unsafe sex failure of contraceptives All of the above 47 During which phase of the pregnancy MTP is safe? (a) (b) (c) (d) 1st trimester 2nd trimester 3rd trimester 4th trimester 48 MTP is of much risk in which phase of the pregnancy? (a) 2nd trimester (c) 1st week (b) 1st trimester (d) 2nd week 49 MTP is being …A… to abort even normal foetus. Specially when sex of the foetus is …B… . Choose the correct option for A and B. (a) A–used, B–male (b) A–misused, B–female (c) A–used, B–abnormal (d) A–misused, B–male 50 The other names for STIs or STDs are (a) venereal diseases (c) Both (a) and (b) (b) reproductive tract infections (d) None of these 51 Hepatitis-B and HIV spread through (a) sharing needles (b) transfusion of blood (c) infected mother to child (d) All of these www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 78 52 Which of the following sexually transmitted diseases is not completely curable? NEET 2019 (a) Genital warts (b) Genital herpes (c) Chlamydiasis (d) Gonorrhoea age group of (a) 15-35 years (c) 15-24 years (b) 15-30 years (d) 15-45 years 56 The timely detection of STIs is hindered by which of 53 Which of the following sexually transmitted diseases do not specifically affect reproductive organs? NEET (Odisha) 2019 (a) Genital warts and Hepatitis-B (b) Syphilis and Genital herpes (c) AIDS and Hepatitis-B (d) Chlamydiasis and AIDS the following factors? (a) (b) (c) (d) Absence of advanced diagnostics Social stigma attached to STIs Initial asymptomatic condition of patients Both (b) and (c) 57 The preventive measures of STIs include (a) (b) (c) (d) 54 STIs caused by bacteria include (a) syphilis (c) Both (a) and (b) 55 Incidence of STIs are very high among persons, in the (b) gonorrhoea (d) hepatitis using condoms avoid multiple sexual partner hygienic sexual practices All of the above TOPIC 4 ~ Infertility 65 Difference between ZIFT and IUT lies in the 58 A couple can be infertile because of (a) physical defect (c) psychological defect (b) congenital defect (d) All of these 59 Assisted reproductive technology, IVF involves transfer of CBSE-AIPMT 2014 (a) ovum into the Fallopian tube (b) zygote into the Fallopian tube (c) zygote into the uterus (d) embryo with 16 blastomeres into the Fallopian tube 60 IVF in which the early zygote with up to 8 blastomeres is transferred to the Fallopian tube is called (a) ZIFT (c) ICSI (b) GIFT (d) IUI CBSE-AIPMT 2012 (a) Intra Cytoplasmic Sperm Injection (ICSI) (b) Intra Uterine Insemination (IUI) (c) Gamete Intra Fallopian Transfer (GIFT) (d) Zygote Intra Fallopian Transfer (ZIFT) (a) Inter Uterine Transfer (b) Intra Uterine Transfer (c) In-Uterus Transfer (d) None of these 63 Embryo with more than 16 blastomeres formed due to in vitro fertilisation is transferred into NEET 2016 (b) Fallopian tube (d) cervix 64 IVF in which embryo with more than 8 blastomeres is transferred into female body is called (a) IUT (c) ZIFT (b) GIFT (d) ICSI 66 Specialised health care units help in diagnosis and corrective treatment of disorders which result in fertility. However, when such connections are not possible, couples are advised (a) (b) (c) (d) in vitro fertilisation Artificial insemination in vivo fertilisation All of the above (a) unable to produce eggs (b) unable to support a foetus (c) unable to provide suitable environment for fertilisation and maturation of foetus (d) All of the above 68 A childless couple can be assisted to have a child 62 IUT Stands for (a) uterus (c) fimbriae methodology nature of the sperms nature of the cells number of the cells 67 GIFT can be advised to couples where female partner is 61 The test tube baby programme employs which one of the following techniques? (a) (b) (c) (d) through a technique called GIFT. The full form of this technique is CBSE-AIPMT 2015 (a) Gamete Inseminated Fallopian Transfer (b) Gamete Intra Fallopian Transfer (c) Gamete Internal Fertilisation and Transfer (d) Germ Cell Internal Fallopian Transfer 69 During ICSI technique, (a) (b) (c) (d) fertilisation is done in vivo embryo transfer is done at 32 blastomere stage sperm directly injected into ovum All of the above www.mediit.in CHAPTER 04 > Reproductive Health 79 70 In case of a couple, where the male is having a very low sperm count, which technique will be suitable for NEET 2017 fertilisation ? (a) (b) (c) (d) Intra Uterine Transfer Gamete Intracytoplasmic Fallopian Transfer Artificial Insemination Intracytoplasmic Sperm Injection (c) transfer of sperms to into Fallopian tube of surrogate (d) transfer of sperms from husband/donor into a test tube containing ova 72 The ‘ART’ in which the semen collected either from the husband or a healthy donor and artificially introduced either into the vagina or into the uterus is 71 Artificial insemination refers to (a) artificial introduction of sperms from a donor into female vagina (b) direct introduction of sperms into ovaries (a) (b) (c) (d) Intra uterine devices Intra uterine insemination Inter uterine insemination Intra cytoplasmic sperm injection NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Directions (Q. No. 73-89) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 73 Assertion (A) A person should be considered 74 75 76 77 reproductively healthy, if he has healthy reproductive organs, but is emotionally imbalanced. Reason (R) It is significant to maintain reproductive health of people and society. Assertion (A) Family planning is an action plan to attain reproductive health. Reason (R) Some additional improved programmes covering reproduction related areas are currently in operation under the Reproductive and child Healthcare Programmes. Assertion (A) Reproductive and Child Healthcare Programme is for reproduction related areas. Reason (R) It deals with creating awareness among various reproduction related aspects. Assertion (A) Amniocentesis is often misused. Reason (R) It is meant for determining the genetic disorders in the foetus, but it is being used to determine the sex of the foetus, leading to increase in the female foeticide. Assertion (A) Rapid decline in death rate, MMR and IMR have lead to staggering rise in population. Reason (R) Such an alarming growth rate has lead to an absolute scarcity of even the most basic requirements, i.e. food and shelter. 78 Assertion (A) Overpopulation has become a serious problem in the developing countries. Reason (R) Developing countries show characteristics such as high fertility, low or rapidly falling mortality rate, rapid population growth and a very young age distribution. 79 Assertion (A) Family planning is done by using contraceptive methods. Reason (R) Natural contraceptive methods include condoms, diaphragms, etc., while barrier methods include periodic abstinence, lactational amenorrhea, etc. 80 Assertion (A) Reusable contraceptives are safe methods of contraceptions. Reason (R) Diaphragms, cervical caps and vaults are barrier methods which prevent conceptions by blocking entry of sperms through cervix. They are reusable. 81 Assertion (A) Contraceptives are methods to prevent unwanted pregnancies. Reason (R) Unwanted pregnancies can only be prevented by using oral contraceptives. 82 Assertion (A) There is chance of fertilisation during 10th-17th days of menstrual cycle. Reason (R) Ovulation can be expected during these days. 83 Assertion (A) Barrier methods prevent conception. Reason (R) These prevent the physical meeting of sperm and ova. 84 Assertion (A) Sterilisation is a surgical method of contraception. Reason (R) It blocks gamete transport and thereby prevents conception. www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 80 85 Assertion (A) Use of condoms is a safeguard against 86 87 88 89 AIDS and sexual diseases besides preventing pregnancy. Reason (R) Certain contraceptives are planted under the skin of the upper arm to prevent pregnancy. Assertion (A) Syphilis, chlamydiasis, Genital herpes and trichomoniasis are STIs. Reason (R) Their incidences are reportedly high in people belonging 15-24 years age groups. Assertion (A) Both male and female can be infertile. Reason (R) Infertile couples can have children with the help of ARTs. Assertion (A) In zygote intra Fallopian transfer, the zygote is transferred to the Fallopian tubes of the female. Reason (R) ZIFT is an in vivo fertilisation method. Assertion (A) Artificial insemination is method of introduction of semen inside the female. Reason (R) This technique is used in those cases where males have low sperm count. II. Statement Based Questions 90 Select the statement which is not a cause of population growth. (a) (b) (c) (d) Decline in death rate Rapid increase in MMR and IMR Rapid decline in MMR and IMR Increase in the number of people in the reproductive age group 91 Identify the incorrect statement(s) from those given below. (a) RCH programmes created awareness among people about various reproduction related aspects (b) Sexually transmitted diseases can be avoided by educating people with proper information about reproduction, adolescence and related changes, etc. (c) Ultrasounds have been banned as it was used for foetal sex-determination based on chromosomal studies (d) All of the above 92 Select the correct statement(s) which includes the steps implemented by government to control the increasing population. (a) Increasing the price of contraceptives so they are available to all (b) Advertising the benefits of small family, slogans like, ‘hum do hamare do’, etc. (c) Raising the marriageable age, females 18 years, males 21 years (d) Both (b) and (c) 93 Which one of the following statement is incorrect in the context of amniocentesis? (a) (b) (c) (d) NEET 2016 It is used for prenatal sex-determination It can be used for detection of Down’s syndrome It can be used for detection of cleft palate It is usually done when a woman in between 14-16 weeks pregnant 94 Which statement is correct for natural methods of contraception? (a) (b) (c) (d) They increase phagocytosis of sperms They employ barriers to prevent fertilisation They are surgical methods and are terminal methods They are natural ways of avoiding chances of fertilisation 95 Diaphragms are the contraceptive devices, used by the females. I. They are introduced into the uterus. II. They are placed to cover the cervical region. III. They act as physical barriers to the sperm entry. IV. They act as spermicidal agents. Choose the correct statements. (a) (b) (c) (d) I and II I and III II and III III and IV 96 Consider the following statements for IUD and choose the correct option. (a) Increases phagocytosis of sperms (b) Releases Cu 2+ ions, suppresses the sperm motility (c) Reduces the fertilising capacity of sperms (d) All of the above 97 Find out the incorrect statement for IUD. (a) They can be self-inserted (b) They are inserted by expert nurses/doctors (c) They may be non-medicated IUDs, copper releasing IUDs or hormone releasing IUDs (d) They are intrauterine devices 98 Which of the following is a correct statement? (a) IUDs once inserted need not be replaced (b) Jellies and cream enable sperms to reach towards ovum speedly (c) IUDs increase phagocytosis of sperms in the uterus (d) Pills suppress gametogenesis in males 99 Which of the following is incorrect regarding vasectomy? NEET 2016 (a) No sperm occurs in seminal fluid (b) No sperm occurs in epididymis (c) Vasa deferentia is cut and tied (d) Irreversible sterility www.mediit.in CHAPTER 04 > Reproductive Health 100 Identify the false statement from the below statements. (a) Genital herpes and hepatitis-B are sexually transmitted diseases caused by virus (b) Syphilis is an STD caused by bacterium Treponema pallidum (c) In India, there is rapid decline in infant mortality rate and MMR (d) Genital warts is a sexually transmitted disease caused by herpes virus 101 Identify the correct statements. (a) Infertility is the inability to produce viable offspring due to the defects in the female or male partner (b) Lactation have no role in preventing conception (c) Abstaining from coitus from day 10-17 of menstrual cycle when ovulation is expected constitutes natural method of contraception (d) Both (a) and (c) 102 Which of the following statements is incorrect about ZIFT? (a) (b) (c) (d) Zygote in the Fallopian transfer Type of IVF Embryo with more than 8 blastomeres are used Zygote or embryo with up to 8 blastomeres are used 103 Which statement is false for GIFT? (a) (b) (c) (d) It is Gamete Intra Fallopian Transfer Ovum is transferred into the oviduct Zygote is transferred into Fallopian tube Used when the receptive is sterile 104 Choose the correct matched statements from the following. I. IUT – Embryo is transferred into the uterus after in vitro fertilisation. II. GIFT – Gametes are collected and injected in the Fallopian tube. III. AI – Taking semen from donor and transferring it into female genital tract. IV. ZIFT – Zygote inserted into the Fallopian tube. V. ICSI – One sperm transferred into the ovum. (a) (b) (c) (d) I, II and III II, III and IV III, IV and V I, II, III, IV and V 105 Choose the WHOs statement about reproductive health. I. Healthy reproductive organs with normal functions. II. Total well-being of physical, emotional, behavioural and social aspects. III. Free of all STD. (a) (b) (c) (d) I and II I and III II and III Only II 81 106 What is true for an ideal contraceptive? I. It should be user-friendly. II. It should be easily available. III. It should be effective and reversible with least side effects. IV. It should be interfering in coitus. V. It should be expensive and effective. Choose the correct option. (a) I, IV and III (c) I, II and III (b) I, IV and V (d) II, IV and V 107 Which of the following statements are correctly associated with Saheli? I. It is a ‘once a week’ pill with very few side effects. II. This contraceptive was a developed at CDRI Lucknow. III. Saheli is an oral pill containing a steroidal preparation. IV. This oral contraceptive is known to cause multiple side effects in women and has low contraceptive value. (a) III and IV (c) I, II and III (b) I and II (d) All of these 108 Identify the correct statements about lactational amenorrhea. I. Ovulation does not occur during the lactational period. II. Chances of the failure of contraception are almost nil up to six months following parturition. III. Side effects are almost nil. IV. It is a natural method of contraception. V. It increases phagocytosis of sperms. (a) II, III, IV and V (c) I, III, IV and V (b) All except V (d) All of these 109 Which statements show the correct purpose of contraceptive pills? I. They inhibit ovulation and implantation. II. They alter the quality of cervical mucus to prevent or retard the entry of sperms. III. They prevent the ejaculated semen from entering the female vagina. IV. They inhibit spermatogenesis. (a) I, II and IV (c) I and II (b) I, II and III (d) I, II, III and IV 110 Identify the false statements regarding the techniques of contraception. I. There are many side effects of tubectomy and vasectomy. II. Purpose of tubectomy is to prevent egg formation. III. The most important component of the oral contraceptive pills is progesterone. IV. Contraceptive oral pills help in birth control by preventing ovulation. (a) I, II and III (c) III, IV and II (b) I and II (d) II and IV www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 82 111 Find out the correct statements about tubectomy. I. The failure rate of this approach is almost zero per cent. II. It is also known as tubal ligation. III. It is more difficult than vasectomy and is even more difficult to reverse. (a) I and II (c) I and III (b) II and III (d) All of these 112 Consider the following statements and choose the correct statements. I. Numerous children have been produced by in vitro fertilisation but with some abnormalities. II. Chances of conception are nil until mother breastfeeds the child for two years. III. Birth control pills are likely to cause cardiovascular problems due to oestrogen present in them. IV. Emergency contraceptive pills may be taken within 72 hours of coitus to prevent conception. (a) III and IV (b) I and III (c) I and II (d) II and III 113 Which of the following given statements are not correct? I. A statutory ban has been implemented on amniocentesis because of its regular misuse. II. Surgical methods are also called sterilisation as they block the release of gametes into secretions. III. All sexually transmitted diseases are completely curable. IV. MTPs are relatively safe up to 20 weeks of pregnancy. (a) I and III (c) II and III (b) III and IV (d) I and II 114 Which of the following statements are false? I. Abortions could happen spontaneously too. II. Oral pills are very popular contraceptives among the rural women. III. Removal of gonads can be considered as a contraceptive option. IV. Sex education is necessary in schools. V. Amniocentesis for sex-determination is banned in our country. Correct option is (a) I, II and III (c) III, IV and V (b) II, III and IV (d) II and III 115 To avoid transmission of STDs. I. Avoid sex with multiple partners. II. Always have unprotected sex. III. Use condoms during coitus. IV. Avoid sex with unknown partners. V. Avoid sharing of needles. Choose the correct option. (a) I and II (c) I and III (b) II, III and IV (d) I, III, IV and V 116 STDs lead to the I. minor complications like itching, fluid discharge, slight pain, swellings. II. major complications like pelvic inflammatory diseases ectopic pregnancies. III. problems like infertility, abortions. IV. cancer of the reproductive tract. Choose the correct option. (a) I, II and IV (c) I, III and IV (b) I, II and III (d) All of these 117 Which of the following statements are correct? I. MTPs are generally advised during first trimester. II. MTP (Amendment) Act, 2017 was enacted by the government of India to reduce illegal abortions. III. Government of India legalised MTP in 1971. IV. MTP during the second trimester can be done in case where the child after birth would suffer from some physical or mental abnormalities. (a) I, II, III, IV and V (c) I, III, IV, V and VI (b) I, II, III, V and VI (d) All of these III. Matching Type Questions 118 Match the following columns. Column I Column II A. Amniocentesis 1. Venereal disease B. Reproductive tract infections 2. Deformed joints and paralysis C. Syphilis 3. Foetal sex-determination D. Gonorrhoea 4. Baby of infected person born blind Codes A (a) 3 (c) 2 B 1 3 C 2 1 D 4 4 A (b) 1 (d) 4 B 2 3 C 3 2 D 4 1 119 Match the following columns. Column I Column II A. Saheli 1. Intra uterine device B. Diaphragms 2. Prevent ovulation and implantation C. Spermicides 3. Prevent sperms from reaching the cervix D. Lippes loop 4. Sperm killing agent Codes A (a) 1 (b) 2 (c) 2 (d) 4 B 2 3 3 3 C 4 4 1 2 D 3 1 4 1 www.mediit.in CHAPTER 04 > Reproductive Health 83 120 Match the following columns. Column I (Infertility conditions) Column II (Features) A. Oligospermia 1. Ovarian cyst formation B. Azospermia 2. Inflammation of ovary due to infection C. Cryptorchidism 3. Decreased sperm count D. Oophorocystosis 4. Absence of living sperms E. Oophoritis 5. Non-descendence of testes from abdominal cavity to scrotum Codes A (a) 3 (b) 1 (c) 5 (d) 4 B 4 2 4 1 C 5 3 3 2 D 1 4 2 5 Column I (STDs) Column II (Causal agents) A. Chlamydiasis 1. Chlamydia trachomatis B. Chancroid 2. Haemophilus ducreyi C. Trichomoniasis 3. Trichomonas vaginalis D. Genital herpes 4. Herpes simplex virus B 3 2 C 2 3 D 4 4 A (b) 4 (d) 1 Column I (STDs) B 1 2 C 3 4 D 2 3 D 2 4 2 3 124 Match the following columns. Column I (Contraceptive methods) Column II (Categories) A. Periodic abstinence 1. Natural methods B. Vasectomy 2. Barrier methods C. Coitus interruptus 3. Surgical methods 1. Zidovudine drug 2. Cryosurgery C. Syphilis 3. Penicillin and tetracycline D. Enterobiasis 4. Antihelminthic tablets E. Lactational amenorrhea F. Cervical caps Codes A (a) 1 (b) 1 (c) 2 (d) 1 B 1 3 1 3 C 2 2 2 1 D 3 1 1 2 E 2 3 3 1 F 3 2 3 2 Column I (Names of IUDs) Column II (Examples of IUDs) A. Non-medicated IUD 1. Progestasert and LNG-20 B. Copper releasing IUD 2. Lippes loop C. Hormone releasing IUD 3. Cu-T, Cu-7 and Multiload-375 Codes A (a) 3 (b) 1 (c) 2 (d) 2 Column II (Treatments) B. Genital warts Codes A (a) 4 (c) 2 C 1 1 4 2 125 Match the following columns. 122 Match the following columns. A. AIDS B 4 3 1 1 D. IUDs E 2 5 1 3 121 Match the following columns. Codes A (a) 1 (c) 1 Codes A (a) 3 (b) 2 (c) 3 (d) 4 B 2 2 3 1 C 1 3 1 3 126 Match the following columns. Column I B 3 4 C 2 1 D 1 3 A (b) 1 (d) 1 B 3 2 C 4 3 D 2 4 A. Government of India legalised MTP in 1. 1951 B. Family planning introduced 2. in India 1971 C. Nirodh 3. Barrier method D. Mala-D and Mala-N 4. Hormonal method 123 Given below are the four methods and their modes of action in achieving contraception. Select their correct matching from the four options that follows. Column I (Birth control measures) Column II (Modes of action) A. Pill 1. Prevents sperms reaching cervix B. Condom 2. Prevents implantation C. Vasectomy 3. Prevents ovulation D. Copper-T 4. Semen contains no sperms Column II Codes A (a) 1 (b) 2 (c) 4 (d) 1 B 2 1 3 4 C 3 3 2 3 D 4 4 1 2 www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 84 Column I 127 Match the following columns. Column I Column II A. Collected gametes are made to form the zygote in the laboratory. 1. In vivo fertilisation B. Zygote or Early embryo with up to 8 blastomeres is transferred into the oviduct. 2. IUT C. Zygote with more than 8 blastomeres, is transferred into the uterus. 3. ZIFT D. Fusion of the gametes in the female reproductive tract. 4. IVF Codes A (a) 4 (b) 3 (b) 4 (d) 2 B 3 1 2 1 C 2 4 3 3 Column II A. Gonorrhoea 1. HIV B. Syphilis 2. Neisseria C. Genital warts 3. Treponema 4. Human papilloma virus D. AIDS Codes A (a) 2 (c) 4 B 3 2 C 4 3 D 1 1 A (b) 3 (d) 4 B 4 3 C 1 2 D 2 1 129 Match Column I with Column II and select the correct D 1 2 1 4 128 Match the following sexually transmitted diseases (Column I) with their causative agent (Column II) and select the correct option. NEET 2017 option from the given codes. Column I (Diseases) Column II (Diagnostic tests) A. Syphilis B. Genital herpes 2. VDRL Test C. AIDS 3. Urine Test D. Gonorrhoea 4. ELISA Codes A (a) 1 (c) 4 B 2 3 C 3 2 1. D 4 1 PCR Test A (b) 2 (d) 3 B 1 4 C 4 1 D 3 2 NCERT Exemplar MULTIPLE CHOICE QUESTIONS 130 A national level approach to build up a reproductively healthy society was taken up in our country in (a) 1950s (c) 1980s (b) 1960s (d) 1990s 131 Increased IMR and decreased MMR in a population will (a) cause rapid increase in growth rate (b) result in decline in growth rate (c) not cause significant change in growth rate (d) result in an explosive population 132 Intensely lactating mothers do not generally conceive due to the (a) suppression of gonadotropins (b) hypersecretion of gonadotropins (c) suppression of gametic transport (d) suppression of fertilisation 133 Condoms are one of the most popular contraceptives because of the following reasons. (a) These are effective barriers for insemination (b) They do not interfere with coital act (c) These help in reducing the risk of STDs (d) All of the above 134 Diaphragms are contraceptive devices used by the females. Choose the correct option from the statements given below. I. They are introduced into the uterus. II. They are placed to cover the cervical region. III. They act as physical barriers for sperm entry. IV. They act as spermicidal agents. (a) I and II (b) I and III (c) II and III (d) III and IV 135 Choose the right one among the statements given below. NEET (Odisha) 2019 (a) IUDs are generally inserted by the user herself (b) IUDs increase phagocytosis reaction in the uterus (c) IUDs suppress gametogenesis (d) IUDs once inserted need not be replaced 136 Emergency contraceptives are effective if used within 72 hrs of (a) coitus (c) menstruation (b) ovulation (d) implantation 137 The correct surgical procedure as a contraceptive method is (a) ovariectomy (c) vasectomy (b) hysterectomy (d) castration www.mediit.in CHAPTER 04 > Reproductive Health 85 141 Sterilisation techniques are generally foolproof 138 From the sexually transmitted diseases mentioned methods of contraception with least side effects. Yet, this is the last option for the couples because I. it is almost irreversible. II. of the misconception that it will reduce sexual urge/drive. III. it is a surgical procedure. IV. of lack of sufficient facilities in many parts of the country. Choose the correct option. below, identify the one which does not specifically affect the sex organs. (a) Syphilis (b) AIDS (c) Gonorrhoea (d) Genital warts 139 Choose the correct statement regarding the ZIFT procedure. (a) Ova collected from a female donor are transferred to the Fallopian tube to facilitate zygote formation (b) Zygote is collected from a female donor and transferred to the Fallopian tube (c) Zygote is collected from a female donor and transferred to the uterus (d) Ova collected from a female donor and transferred to the uterus (a) I and III (c) II and IV (b) II and III (d) I, II, III and IV 142 Following statements are given regarding MTP. assisted by reproductive technology is called Choose the correct option given below. I. MTPs are generally advised during first trimester. II. MTPs are used as a contraceptive method. III. MTPs are always surgical. IV. MTPs require the assistance of qualified medical personnel. (a) GIFT (c) ICSI Codes (a) I and III 140 The method of directly injecting a sperm into ovum is (b) ZIFT (d) ET (b) II and III (c) I and IV (d) I and II Answers Mastering NCERT with MCQs 1 (d) 2 (a) 3 (a) 4 (a) 5 (a) 6 (d) 7 (d) 8 (b) 9 (c) 10 (d) 11 (d) 12 (c) 13 (b) 14 (b) 15 (b) 16 (b) 17 (a) 18 (c) 19 (c) 20 (b) 21 (c) 22 (b) 23 (d) 24 (d) 25 (b) 26 (b) 27 (c) 28 (b) 29 (b) 30 (b) 31 (c) 32 (b) 33 (a) 34 (c) 35 (a) 36 (a) 37 (a) 38 (c) 39 (d) 40 (a) 41 (b) 42 (c) 43 (c) 44 (d) 45 (a) 46 (d) 47 (a) 48 (a) 49 (b) 50 (c) 51 (d) 52 (b) 53 (c) 54 (c) 55 (c) 56 (d) 57 (d) 58 (d) 59 (b) 60 (a) 61 (d) 62 (b) 63 (a) 64 (a) 65 (d) 66 (d) 67 (d) 68 (b) 69 (c) 70 (c) 71 (a) 72 (b) 77 (b) 78 (b) 79 (c) 80 (a) 81 (c) 82 (a) 83 (a) 84 (a) 85 (b) 86 (b) 87 (b) 92 (d) 93 (c) 94 (d) 95 (c) 96 (d) 97 (a) 98 (c) 99 (b) 100 (d) 101 (d) 102 (c) NEET Special Types Questions 73 (d) 88 (c) 103 (c) 74 (b) 75 (a) 76 (a) 89 (a) 90 (b) 91 (c) 104 (d) 105 (d) 106 (c) 118 (a) 119 (b) 120 (a) 121 (c) 107 (b) 108 (b) 109 (c) 122 (d) 123 (c) 110 (b) 111 (d) 112 (a) 113 (b) 114 (d) 115 (d) 116 (d) 117 (d) 124 (d) 125 (c) 126 (b) 127 (a) 128 (a) 129 (b) NCERT Exemplar Questions 130 (a) 131 (c) 132 (a) 133 (d) 134 (c) 135 (b) 136 (a) 137 (c) 138 (b) 139 (b) 140 (c) 141 (a) 142 (c) Answers & Explanations 1 (d) The term ‘reproductive health’ simply refers to healthy 5 (a) Amniocentesis is a foetal sex-determination test based on reproductive organs with normal functions. However, in broader perspectives it includes a total well-being in all aspects of reproduction, i.e. emotional, behavioural, physical and social. 4 (a) Reproductive health can be improved by educating and creating awareness among the people about various aspects of reproductive health. the analysis of chromosomal pattern using the amniotic fluid surrounding the developing embryo. 6 (d) Jaundice is a condition not based on chromosomal pattern, hence it cannot be detected by amniocentesis. It is a disease related to liver dysfunctioning. 7 (d) There are some indicators of improved reproductive health of the society. These include better awareness about www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 86 12 14 15 18 19 20 Answers & Explanations 21 25 26 27 sex related problems, pre-natal care of the mother, medically assisted deliveries, post-natal care of the mother and infant, decrease maternal and infant mortality, small families, better detection and cure of Sexually Transmitted Diseases (STDs), increased medical facilities for sex related problems, etc. (c) An ideal contraceptive should be user-friendly, easily available, effective and reversible with no or least side effects. It also should in no way interfere with the sexual drive, desire and/or the sexual act of the user. (b) One of the legal method of birth control is periodic abstinence in which couples abstain from coitus from day 10-17 of the menstrual cycle. For other options, Abortion by taking medicine is not a legal method. A day break coitus may increase the chances of contraception. A premature ejaculation during coitus will result in fertilisation. (b) Periodic abstinence is avoiding sex during ovulatory phase, i.e. from day 10th-17th of the menstrual cycle. It is also known rhythm method. It is done as a contraceptive method because chances of fertilisation are very high during this period. (c) Lactational amenorrhea is the absence of menstruation during lactation. It is a natural contraception method in which the chances of conception are almost nil in a breastfeeding mother due to the absence of ovulation. This method is effective only up to a maximum period of six months after childbirth. (c) Condoms or Femidoms are barriers made up of thin rubber/ latex sheath that are used to cover the penis in the male or vagina and cervix in the female, just before coitus. So, that the ejaculated semen would not enter into the female reproductive tract. (b) Diaphragms, cervical caps and vaults are barrier method used by females only. These are made up of rubber that are inserted into the female reproductive tract to cover the cervix during coitus. They prevent conception by blocking the entry of sperms through the cervix. They are reusable. (c) Spermicidal creams contain chemicals, which kill the sperms. If they are used along with the barrier contraceptive methods, then these increases contraceptive efficiency. (b) Depo-provera is an injectible form of the hormone based contraception. These are progesterone derivative injections, which are taken every two-three months. These release hormone slowly and prevent ovulation. (b) Progestasert and LNG-20 are hormone releasing Intra Uterine Devices (IUDs). These devices release small quantities of hormone which suppresses endometrial changes, ovulation and causes insufficient luteal activity. (c) The copper releasing IUDs, release Cu + ions which suppress the sperm motility and the fertilising capacity of sperms. 30 (b) The females wanting to delay pregnancy or space 31 32 34 35 38 39 40 42 children should use IUDs, i.e. Intra Uterine Devices. These provide long term but reversible contraception. Other options like tubectomy is an irreversible method and femidoms, vaults and caps are barrier methods which do not provide long term contraception. (c) Oral contraceptives have hormonal preparation of small doses of either progesterone or progesterone-oestrogen combination in the form of tablets. These are used by females. (b) Pills have to be taken daily for 21 days starting within the first 5 days of menstrual cycle. After a gap of 7 days (during which menstruation occurs) these has to be repeated in the same pattern till the female desires to prevent conception. (c) The oral contraceptive ‘Saheli’ blocks oestrogen receptors in the uterus preventing eggs from getting implanted. It is a type of mini pill that contains a non-steroidal preparation centchroman. It is taken once in a week after an initial intake of twice a week dose for 3 months. This non-hormonal preparation contains progestin only and no oestrogen. (a) Implants, i.e. six matchstick-sized capsules containing steroids are inserted under the skin of the inner arm above the elbow. These steroid capsules slowly release the synthetic progesterone or progesterone-oestrogen combination for about 5 years. (c) Option (c) is correct. As hormonal implants and oral contraceptives have the same combination of oestrogen and progesterone hormones. Their mode of working is same but the site of implantation is different, i.e. implants are placed under the skin, while oral contraceptives are orally consumed. The duration of their effective period also varies since implants have long lasting effects compared to pills. (d) Lactational amenorrhea, pills and emergency contraceptives provide contraception due to the role of hormones. In lactational amenorrhea, high prolactin level during active lactation period decreases the gonadotropin level in the blood. Pills usually contain progesterone or progesterone-oestrogen hormonal combinations which prevent ovulation. Emergency contraceptives also contain progesterone and oestradiol preparations. Other contraceptive methods include barrier method, represent a physical method of contraception. Also, copper-T (Cu-T) acts by releasing copper and not any hormone. (a) Tubectomy is a sterilisation method of contraception. During this procedure, a small part of the Fallopian tube in females is removed or tied up and blocked to restrict the entry of sperms reaching the ova. It is a permanent birth control method. (c) Option (c) does not give the defined action of contraceptive. It can be corrected as Vasectomy prevents transport of sperms and not its production, i.e. spermatogenesis. www.mediit.in 44 47 50 51 52 53 55 In this method of contraception, small part of vas deferens is removed or tied up through a small incision on the scrotum. (d) Sterilisation techniques include vasectomy and tubectomy. These are very reliable methods of birth control, because their approximate failure rate is less than 1%. (a) MTP (Medical Termination of Pregnancy) is considered as safe until Ist trimester (12 weeks) of the pregnancy. It becomes more risky after the Ist trimester period of pregnancy, as the foetus becomes intimately associated with the maternal tissue. (c) The other name for Sexually Transmitted Diseases (STDs) are Venereal Diseases (VDs) or Reproductive Tract Infections (RTIs). These diseases or infections are transmitted through sexual intercourse with infected persons. (d) Mode of infection of AIDS and hepatitis-B are same. These diseases spread from an infected person to healthy person through sharing of needles, transfusion of blood and from infected mother to child. Both diseases are also incurable. (b) Genital herpes is a sexually transmitted disease which is not completely curable. It is caused by type-II herpes simplex virus. Treatment is available for herpes symptoms, but the virus is unaffected and remains in the body, thus can becomes active again. (c) AIDS and Hepatitis-B are sexually transmitted diseases which do not specifically affect reproductive organs. AIDS affects the overall immune system of the individual and hepatitis-B affects the liver. These are called STDs because they spread through via body fluids unsafe sex or use of needles, etc. (c) Incidence of STIs or STDs are very high among persons in the age group of 15-24 years. This is due to the fact that young people l l l l Have multiple sex partners. Engage in unprotected sex. Use drugs and alcohol at high rate. Engage in high risk behaviours, while under the influence of drugs and /or alcohol. 64 65 66 68 69 70 73 74 58 (d) A large number of couples are unable to produce children inspite of unprotected sex, i.e. are infertile. The reasons for this could be physical, congenital diseases, drugs, immunological or even psychological defect. 59 (b) IVF is an Assisted Reproductive Technology (ART) that involves transfer of zygote into Fallopian tube. In vitro fertilisation is a process in which an egg is fertilised by sperm outside the woman’s womb and the zygote up to 8-celled stage is implanted into the Fallopian tube. IVF is a major treatment for infertility. 60 (a) In ZIFT (Zygote Intra Fallopian Transfer), the zygote up to 8-celled stage is transferred to Fallopian tube, rest of the development takes place as that of the natural zygote in the uterus. 61 (d) The test tube baby programme is a method involving In Vitro Fertilisation (IVF). It employs the technique of 75 Zygote Intra Fallopian Transfer (ZIFT) as only in this technique, fertilisation allowed to occur outside the body in laboratory. (a) If an embryo containing more than 8 blastomeres (cells) is transferred into uterus of female’s body then, it is called as IUT (Intra Uterine Transfer). It is also a method of IVF. (d) Difference between ZIFT and IUT lies in the number of the cells. As in ZIFT, the embryo or zygote transfer is done up to 8 blastomere stage and in IUT, the embryo transfer is done when embryo is above 8 blastomere stage. (d) IVF (In Vitro Fertilisation), AI (Artificial Insemination) and in vivo fertilisation are all procedures of ART (Assisted Reproductive Technologies). When the correction of infertility related disorders is not possible couples are advised to have children through these processes. (b) The full form of GIFT is Gamete Intra Fallopian Transfer. It is a technique in which ovum is transferred into the Fallopian tube of another female, who cannot produce one, but can provide suitable environment for fertilisation and further development. (c) ICSI (Intra Cytoplasmic Sperm Injection) is a technique in which a sperm is directly injected into the ovum to form the zygote and further into an embryo in the laboratory (in vitro). This embryo is then transferred into the uterus or Fallopian tube as required. (c) Artificial insemination is commonly used in cases, where male partners are unable to inseminate the female due to very low sperm counts in the ejaculate. In this method, the semen is collected either from husband or a healthy donor and then artificially introduced into the vagina or into the uterus of the female. (d) Assertion is false, but Reason is true. Assertion can be corrected as According to the World Health Organisation (WHO), a person is reproductively healthy when he is physically, emotionally, behaviourally and socially healthy, i.e. overall healthy. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. The correct explanation is as follows Family planning is an action plan mediated by RCH (in 1952) to achieve population stabilisation goals and also promotes reproductive health, reduces maternal, infant and child mortality. This was achieved by delaying the childbirth till mother is over 20 yrs of age, spacing between children and limited size of family. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Reproductive and Child Healthcare (RCH) programmes were initiated in 1951 by government of India to deal with reproduction related areas. These programmes are aimed at creating awareness among people about various aspects such as sex education, reproduction and STDs, knowledge of birth control and pregnancy, sex abuse, etc. Answers & Explanations 87 CHAPTER 04 > Reproductive Health www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 88 76 (a) Both Assertion and Reason are correct and Reason 77 78 79 Answers & Explanations 80 81 82 is the correct explanation of Assertion. Amniocentesis, a medical procedure used in prenatal diagnosis of chromosomal abnormalities and foetal infections is being misused for determining the sex of unborn foetus. If the sex comes is revealed as female, it is followed by medical termination of foetus. This has lead to an increase in the number of female foeticide in our country and is major reason for a ban being implemented on it. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The correct explanation is as follows Rapid decline in death rate, MMR (Maternal Mortality Rate) and IMR (Infant Mortality Rate) have all happened due to significant improvement in quality of life, increased medical facilities, awareness about reproduction related facts such as pre and post- natal care of mother’s vaccination of children, etc., supported by better living conditions. As a result, there has been a staggering rise in population. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. The correct explanation is as follows Overpopulation has become a serious problem in the developing countries because of the improved medical facilities and quality of life. (c) Assertion is true, but Reason is false. Reason can be corrected as Contraceptives help in family planning by inhibiting fertilisation of gametes. Natural methods work on the principle of avoiding chances of ovum and sperms meeting, e.g. periodic abstinence, lactational amenorrhea. In barrier methods, ovum and sperm are prevented from physically meeting with the help of barrier, e.g. condoms, cervical caps, diaphragms, etc. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Reusable contraceptives are safe methods because they prevent exchange of body fluids during intercourse by preventing the entry of sperms into vagina and uterus. These include diaphragms, cervical caps, vaults, etc., and are inserted before intercourse and can be reused. (c) Assertion is true, but Reason is false. Reason can be corrected as Contraceptive can be broadly grouped into natural, barrier, IUDs, oral contraceptives, injectables, implants and surgical methods. These all methods are used to prevent unwanted pregnancies. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. There is a chance of fertilisation during 10-17 days of menstruation cycle because most in females, ovulation is expected to occur during these days. Thus, the couple paracticing periodic abstinence refrains from sexual intercourse during this period. 83 (a) Both Assertion and Reason are correct and Reason 84 85 86 87 88 90 91 93 is the correct explanation of Assertion. Barrier methods prevent conception because they do not allow the ovum and sperms to physically meet, thereby preventing fertilisation, e.g. condoms, diaphragms, etc. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Sterilisation is a surgical method of contraception as it blocks the transport of gametes and hence prevent fertilisation. The process is called as vasectomy in males and tubectomy in females. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The correct explanation is as follows Condoms act as a barrier that prevents the male ejaculate from entering female body and thus avoids conception and also prevents the transmission of STDs such as AIDS. In females, implants are placed under the skin as the method of contraceptive. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The correct explanation is as follows Syphilis, chlamydiasis, genital herpes and trichomoniasis are STIs because they spread from infected person to other through sexual contact or unsafe, unhygienic sexual practices. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. Both male and female can be infertile, i.e. unable to conceive or bear children. This can happen because of various reasons which can be physical congenital immunological or even psychological disorders, e.g. cryptorchidism, hyperthermia STDs, alcoholism (in males), PCOs, blocked Fallopian tube, irregular menstrual cycle, etc (in females). (c) Assertion is true, but Reason is false. Reason can be corrected as ZIFT is an in vitro fertilisation method, in which zygote is transferred into Fallopian tube of the female. (b) Statements in option (b) is not a cause for population growth. As a rapid increase in IMR and MMR contributes to population growth. Other options are correct. (c) Statement in option (c) represents the incorrect statement and can be corrected as Amniocentesis was banned by government due to its misuse in detection of sex of child based on chromosomal studies. This information lead to an increase in female foeticides. Rest of the statements are correct. (c) Statement in option (c) represents the incorrect statement and can be corrected as Cleft palate is a developmental abnormality which may occur in the developing foetus. So, it can be detected by sonography, not by amniocentesis. Rest of the statements are correct. www.mediit.in 89 CHAPTER 04 > Reproductive Health 94 (d) Statement in option (d) is correct about natural method 106 (c) Statements I, II and III are characteristics of an of contraception. Natural methods of contraception include lactational amenorrhea, coitus interruptus and periodic abstinence. These methods work on the natural ways to avoiding chances of ovum and sperm meeting. While other statements are related to barrier methods. 97 (a) The statement in option (a) is incorrect about IUD. It can be corrected as Intra Uterine Devices (IUDs) are popular methods of contraception. These devices are inserted by doctors or expert nurses in the uterus through vagina. Rest other statements are correct for IUDs. 98 (c) Statements in option (c) is correct. Other statements are incorrect and can be corrected as ideal contraceptive. An ideal contraceptive should be user friendly, easily available, effective and reversible with least side-effects. It also should not interfere with the sexual drive, desire and sexual act of the user. 107 (b) Statements I and II are correct for Saheli pills. ‘Saheli’ a new oral contraceptive for females was developed at CDRI in Lucknow. It is once in a week pill with non-steroidal preparation. It has few side effects and a high contraceptive value. 108 (b) All statements are correct except (V). It can be corrected as Lactational amenorrhea is based on the fact that ovulation does not occur during lactation, so chances of conception are almost nil, up to six months following parturition. It is a natural method of contraception associated with the females, whereas phagocytosis of sperms is associated with males. 109 (c) Statements I and II show the correct purpose of contraceptive pills. Statements III and IV are incorrect and can be corrected l l IUDs can be removed as these are a reversible contraception method. Jellies are cream are spermicidal and immobilise the sperms. Pills inhibits ovulation and implantation in females. 99 (b) Statement in option (b) gives incorrect information 100 101 102 103 105 regarding vasectomy.It can be corrected as Sperms are produced by testes in the male reproduction system and sent to the epididymis by vasa efferentia and are temporarily stored here. These sperms do not reach to seminal vesicle when vas deferens is cut and tied in vasectomy. (d) Statement in option (d) is false. It can be corrected as Genital warts is a sexually transmitted disease caused by Human Papilloma Virus. (HPV). (d) Statements in option (a) and (c) are correct. Statement in option (b) is incorrect. It can be corrected as Lactation prevents conception because ovulation and menstrual cycle does not occur during the period of intense lactation up to 6 months following parturition. (c) Statement in option (c) represents the incorrect statement about ZIFT. It can be corrected as In ZIFT, zygote or embryo up to 8-cells is transferred to the Fallopian tubes. Embryos with more than 8 blastomeres are used in IUT (Intra Uterine Transfer). (c) Statement in option (c) represents the false statement. It can be corrected as In GIFT (Gamete Intra Fallopian Transfer), gamete (ovum) from donor is transferred into the Fallopian tube of female who can provide suitable environment for fertilisation and foetal growth, but cannot produce ova. (d) Statement II is correct about WHOs. According to the World Health Organisation (WHO), reproductive health means a total well-being in all aspects of reproduction, i.e. physical, emotional, behavioural and social. Therefore, a society with people having physically and functionally normal reproductive organs and normal emotional and behavioural interactions among them in all sex related aspects might be called reproductively healthy. l l Condoms prevent the ejaculated semen from entering the female vagina. Contraceptive pills have not effect on spermatogenesis. 110 (b) Statements I and II are false and can be corrected as l l There are little or no side effects of tubectomy and vasectomy. The purpose of tubectomy is to block the passage of ova. Rest of the statements are correct. 112 (a) Statements III and IV show the correct statement. Statements I and II are incorrect. These can be corrected as l l Chances of conception are nil until the mother breastfeeds child up to six months following parturition. Children produced by IVF are not born with abnormalities. An abnormality will only occur if the donor gamete has some genetical abnormality in it. 113 (b) Statements III and IV are incorrect. They can be corrected as l l Sexually transmitted diseases are completely curable except hepatitis-B, genital herpes and HIV infections. MTPs are relatively safer up to 12 weeks of pregnancy. Rest other statements are correct. 114 (d) Statements II and III are correct and can be corrected as l l Contraceptive oral pills are most popular among urban women. Removal of gonads is not a contraceptive procedure. Rest other statements are true. Answers & Explanations l www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 90 115 (d) Statements I, III, IV and V are correct. Statement II is incorrect and can be corrected as To avoid transmission of sexually transmitted diseases, one should always practice safe sex, i.e. have protected sex by using condoms during coitus. 130 (a) India was amongst the first country in the world to initiate action plans and programmes at a national level to attain total reproductive health as a social goal. These programmes called ‘family planning’ were initiated in 1950s and were periodically assessed over the past decades to determine their effects. 131 (c) IMR (Infant Mortality Rate) and MMR (Maternal Mortality Rate) both are responsible for affecting the growth rate inversely. Here, if IMR has been increased then it will result in decline in growth rate. While, decreased MMR will cause rapid increase in growth rate. Therefore, in the above situation, if IMR has been increased and MMR has been decreased in a population, it will not cause any significant change in growth rate. 132 (a) Breastfeeding is one of the natural contraceptive methods. It is known to suppress the production of Gonadotropin-Releasing Hormone (GnRH) and Follicle Stimulating Hormone (FSH). The release of these hormones triggers ovulation. Breastfeeding also leads to increased level of prolactin, a hormone that inhibits ovulation. So, intensely lactating mothers do not generally conceive due to the suppression of gonadotropins. 133 (d) Condoms are barriers made of thin rubber/latex Answers & Explanations sheath used to cover the penis in the males or vagina and cervix in females. It prevents the deposition of ejaculated semen into the vagina of the female. They do not interfere with coital activity and protects the user from contracting STDs. 134 (c) Option (c) represents the correct statements. Diaphragms are physical barriers made of rubber that are inserted into the female reproductive tract to cover the cervix during coitus. They prevent the entry of sperms through cervix. 135 (b) Option (b) represents the right statement. Other statements are incorrect and can be corrected as l l l IUDs are inserted by doctors or expert nurses in the uterus through vagina. They do not suppress gametogenesis. IUDs can be replaced whenever needed by the females. 136 (a) Administration of higher doses of progestogens or progestogen-oestrogen combinations within 72 hrs of 137 138 139 140 141 coitus have been found to be very effective as emergency contraceptives as they could be used to avoid possible pregnancy due to rape or casual unprotected intercourse. These drugs delay/disrupt the ovulation and fertilisation process. (c) The correct surgical procedure as a contraceptive method is vasectomy performed in males, while in females, is called tubectomy. (b) AIDS (Acquired Immuno Deficiency Syndrome) is a set of symptoms caused by HIV virus in humans. It is transmitted through sexual contact from infected to a healthy person. The HIV virus does not directly affect sex organs as such but produces other set of symptoms in the body of infected person. (b) The correct statement regarding ZIFT is option (b). The zygote or early embryo with up to 8 blastomeres is collected from a female donor and transferred into the Fallopian tube, this process is called Zygote Intra Fallopian Transfer or ZIFT. Embryo more than 8 blastomeres is transferred into the uterus by the process called Intra Uterine Transfer or IUT. When ovum is collected from donor and transferred to Fallopian tube of other female who cannot produce ovum, this is known as Gamete Intra Fallopian Transfer (GIFT). (c) ICSI (Intra Cytoplasmic Sperm Injection) is a specialised procedure to form an embryo in the laboratory in which a sperm is directly injected into the ovum placed in a nutrient broth. (a) Statements I and III represent the correct reason for why couples choose sterilisation techniques as a last option for contraception. Statements II and IV are incorrect and can be corrected as l l Sterilisation techniques have no effect on the sexual urge/drive. At present sufficient facilities are available in most parts of our country for couples who want to undergo sterilisation procedures. 142 (c) Statements I and IV are correct, while statements II and III are incorrect regarding MTPs. MTPs are done to get rid of unwanted pregnancies either due to casual unprotected intercourse or failure of the contraceptive used during coitus or rapes. MTPs are also essential in certain cases where continuation of the pregnancy could be harmful or even fatal either to the mother or to the foetus or both. So, it requires the assistance of qualified medical personnel. www.mediit.in CHAPTER > 05 Principles of Inheritance and Variation NEET Å KEY NOTES Genetics is the branch of biology which deals with the inheritance and variation of characters from parents to their offspring. Mendel’s Laws of Inheritance Å Gregor Mendel conducted hybridisation experiments on garden peas for seven years (1856-1863). He applied statistical analysis and mathematical logic while studying inheritance patterns. Å Mendel investigated two opposing traits of 14 characters in true breeding pea plant (produced by continuous self-pollination and which showed stable trait inheritance). The characters selected by Mendel are tabulated below Contrasting Traits Studied by Mendel in Pea Traits Inheritance of One Gene Å Mendel observed one trait or character at a time, e.g. he crossed a tall and a dwarf pea plants to study the inheritance of one gene. Å He hybridised plants with alternate forms of a single trait (monohybrid cross). The seeds produced by these crosses were grown to develop into plants of Filial1 progeny or F1-generation (F1 -plants). Å Mendel then self-pollinated the tall F1-plants to produce plants of Filial 2 progeny or F2 -generation ( F2 -plants). Å In later experiments, Mendel also crossed pea plants with two contrasting characters known as dihybrid cross. Mendel’s Observation Å S. No. Characters Dominant Recessive 1. Stem height Tall Dwarf 2. Flower colour Violet White 3. Flower position Axial Terminal 4. Pod shape Inflated Constricted 5. Pod colour Green Yellow 6. Seed shape Round Wrinkled 7. Seed colour Yellow Green Å Å Å Å In F1 -generation, Mendel found that all pea plants were tall and none was dwarf. He also observed other pair of traits and found that F1-plant always resembled either one of its parent and the trait of other parent was not found. In F2 -generation, he found that some of the offspring were ‘dwarf ’, i.e. the characters which were not seen in F1-generation were expressed in F2 - generation. The proportion of plants that were dwarf, were 1/4th of the F2 -plants, while 3/4th of the F2 -plants were tall. These contrasting traits (tall/dwarf) did not show any mixing either in F1 or in F2 - generation as none was of intermediate height. www.mediit.in Master The NCERT > Biology (Vol-II ) 92 Similar results were obtained with the other traits that he studied. Only one of the parental traits was expressed in F1-generation, while in F2 - generation stage, both the traits were expressed in the ratio of 3 : 1. Å Mendel also found identical results in dihybrid cross as in monohybrid cross. Mendel’s Inferences Following inferences were made by Mendel based on his observations Å Mendel proposed that factors or genes pass down from parent to offspring through gametes over successive generations. Å Genes are units of inheritance and they code for a pair of contrasting traits called alleles (different forms of the same gene). Å The alleles of a character are denoted as capital and small letters, e.g. T(tall) and t(dwarf). Å Genotype is the genetic constitution of an individual while the phenotype is the external appearance. Å Dominant allele The factor or an allele pair, which can express itself in both homozygous and heterozygous states. Å Recessive allele The factor or allele pair, which can express only in homozygous state. Å Homozygous condition The state in which an organism has two similar genes or alleles of a particular character, e.g. TT or tt for tallness or dwarfness. Å Heterozygous condition In this, an organism contains two different alleles for a particular character, e.g. Tt. Å In a monohybrid cross, genes controlling one character (e.g. height) are considered, e.g. cross between TT × tt (Tall × Dwarf plant). The resultant F1 progeny in such a cross is heterozygous (Tt). In F2 -generation, the recessive parental trait is expressed without any blending which represents that alleles of parental pair segregate during gamete formation. It is a random process. Å Punnett square is the diagrammatic representation of gametes produced by the parents, the formation of the zygotes and F1 , F2 plants. It helps to calculate the probability of all possible genotypes of offspring in a genetic cross. It was developed by British geneticist, Reginald C Punnett. Å Test cross is performed between the dominant phenotype (obtained in F1 or F2 ) and recessive parent, so as to determine the genotype of former. The resultant progeny appear in ratio 1 : 1. ww (White flowers) Interpretation Result Å tt (Dwarf) Parental TT Tt Tt Selfing tt F2-generation Phenotypic ratio – 3 : 1 Genotypic ratio – 1 : 2 : 1 NEET Unknown flower is heterozygous dominant Based on his observations on monohybrid crosses, Mendel proposed two general rules in order to consolidate his understanding of inheritance in monohybrid crosses. Today, these rules are called the principles or laws of inheritance. These are Law of Dominance (First Law) Å Å F1-generation t Unknown flower is homozygous dominant Å Å T (Violet flowers) Ww Ww W Dominant phenotype w ww ww All flowers violet (Genotype unknown) 50% flowers violet 50% flowers white Reciprocal cross A cross in which same two parents are used in such a way that if in one experiment ‘A’ is used as female parent and ‘B’ is used as male parent, in other experiment ‘A’ will be used as male parent and ‘B’ is used as female parent is called reciprocal. t Tt (Tall) w w W Ww Ww Å Å T WW or Ww w Back cross The cross of an organism with the organism of its previous generation is known as back cross. n × w Å n TT (Tall) w w w w Ww Ww W ww Homozygous (White flowers) recessive Characters are controlled by discrete units called factors. Factors occur in pairs. In a dissimilar pair of factors, one member of the pair is dominant while the other is recessive. This law is used to explain the expression of only one of the parental characters in a monohybrid cross in the F1-generation and the expression of both in the F2 -generation. It also explains the proportion of 3:1 ratio obtained in the F2 -generation. Law of Segregation (Second Law) Å This law states that, though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other, such that a gamete receives only one of the two factors. KEY NOTES www.mediit.in 93 CHAPTER 05 > Principles of Inheritance and Variation Å Hence, alleles do not show any blending and both the characters are recovered as such in the F2 -generation, though one of these is not seen in the F1-generation. Å All the patterns of inheritance could not be explained exclusively on the basis of Mendel’s original principles alone and certain complexities were observed by later workers which deviated from Mendel’s laws or Mendelism. 1. Incomplete Dominance Å The F1 -progeny develop a new phenotype which do not resemble either of the two parents and lies in between the two. For example, inheritance of flower colour in snapdragon (Antirrhinum) . Å In this case, both phenotypic and genotypic ratio is 1 : 2 : 1. The phenotypic ratio deviates from the Mendelian ratio of 3 : 1. Å Å Based upon this, Mendel proposed a second set of generalisations or postulates which is called law of independent assortment. Law of Independent Assortment (Third Law) This law states that ‘when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters’ at the time of gamete formation. It also gets randomly rearranged in the offspring producing both parental and new combinations of characters. This can be understood from the figure given below Parents (Round yellow) RRYY Incomplete dominance result due to the production of non-functional enzyme or no enzyme by the recessive allele. RY (Wrinkled green) rryy ry Gametes 2. Codominance Å Å Å The F1 -progeny resemble both the parents due to the equal expression of both alleles. For example, ABO blood group in humans is controlled by gene I which exhibit three alleles–IA , I B and i. IA and I B are codominant alleles and these both are dominant over i. Due to the presence of three different alleles, six genotype of human ABO blood groups are possible. These are tabulated below Table Showing the Genetic Basis of Blood Group in Human Population Allele from Parent 1 Allele from Parent 2 Genotype of Offspring Blood Group of Offspring IA IA IA IA A IA AB IB IA IB A I i A I i A IB IA IA IB AB IB IB IB IB B B I i IB i B i i ii O 3. Multiple Allelism Å More than two alleles governs the same character. These are found during population studies. The human blood group gene provides an example of multiple allele as well as an interesting dominance relationship. Inheritance of Two Genes Å Å To verify his results of monohybrid cross, Mendel also crossed pea plants differing in two characters (dihybrid cross). This helped him to understand inheritance of two genes (i.e. two pairs of alleles) at a time. It was found that inheritance of one pair of allele (one trait) does not interfere in the inheritance of other pair of allele (second trait). (Round yellow) RrYy On selfing RY F1-generation RY Gametes Gametes rY Ry ry RRYy RrYy RrYy RRyy Rryy ry RRYy rrYY rrYy Ry RrYY RrYY RrYy rY RRYY RrYy rrYy F2-generation Rryy rryy Phenotypic Ratio Round yellow : Round green : Wrinkled yellow : Wrinkled green = 9 : 3 : 3 : 1 Result of dihybrid cross where the two parents differed in two pairs of contrasting traits, i.e. seed colour and seed shape In 1900, de Vries, Correns and von Tschermak rediscovered Mendel’s results independently. Due to microscopy, they carefully observed cell division. This led to discovery of chromosomes (structure in the nucleus that appeared in pairs and divide just before each cell division). Chromosomal Theory of Inheritance It was proposed independently by Walter Sutton and Theodore Boveri in 1902. They united the knowledge of chromosomal segregation with Mendelian principles and NEET KEY NOTES www.mediit.in Master The NCERT > Biology (Vol-II ) 94 called it chromosomal theory of inheritance. According to this theory Å All hereditary characters must be with sperms and egg cells as they provide bridge from one generation to the other. Å The hereditary factors must be carried by the nuclear material. Å Chromosomes are also found in pairs like the Mendelian alleles. Å The two alleles of a gene pair are located on homologous sites on the homologous chromosomes. Å The sperms and eggs have haploid sets of chromosomes, which fuse to re-establish the diploid state. The genes are carried on to the chromosomes. Homologous chromosomes synapse during meiosis and get separated to pass into different cells. This is the basis for segregation and independent assortment. Comparison between the Behaviour of Chromosomes and Genes Å Å Chromosomes Genes These occur in pairs. These also occur in pairs. Å Thus, linkage is a phenomenon of genetic inheritance in which genes of a particular chromosome show their tendency to inherit together. Å Morgan and his group also found that even when genes were grouped on the same chromosome, some genes were tightly linked, i.e. linkage is stronger between two genes, if the frequency of recombination is low. Å Whereas, the frequency of recombinations is higher, if genes are loosely linked, i.e. linkage is weak between two genes. Å Recombination of linked genes is by crossing over (exchange of corresponding parts between the chromatids of homologous chromosomes). Polygenic Inheritance Å It was given by Galton in 1833. In this, traits are controlled by three or more genes (multiple genes). These traits are called polygenic traits. Å The phenotype shows participation of each allele and is also influenced by the environment and is called quantitative inheritance as the character/phenotype can be quantified. For example, human skin colour which is caused by a pigment melanin. The quantity of melanin is due to three pairs of polygenes (A, B and C). Å If a black or very dark (AA BB CC) and white or very light (aa bb cc) individuals marry each other, the offspring show intermediate colour, also called mulatto (Aa Ba Ca). A total of eight allele combinations are possible in the gametes, forming 27 distinct genotypes. Segregate at the time of gamete Segregate at gamete formation and formation such that only one of only one of each pair is transmitted to a each pair is transmitted to a gamete. gamete. One pair segregates independently of other pairs. Å Å Å One pair segregates independently of another pairs situated on different chromosome. However, segregation of linked genes shows dependency on each other. It was done by Thomas Hunt Morgan and his colleagues. Morgan carried out various dihybrid crosses in Drosophila with the genes that were sex-linked, i.e. the genes present on the X-chromosome. Morgan selected fruitfly, Drosophila melanogaster for his experiments because They could be grown on simple artificial medium in the laboratory. Their life cycle is only about two weeks. A single mating could produce a large number of flies. It has four pairs of chromosomes which differ in size. There was a clear differentiation of the sexes, i.e. male (smaller) and female (bigger). Pleiotropy Å It is the phenomenon in which a single gene product may produce multiple or more than one phenotypic effect. Å For example, phenylketonuria, a disorder caused by mutation in the gene coding the enzyme phenylalanine hydroxylase. The affected individuals show hair and skin pigmentation and mental retardation. Å Therefore, it can be said that dominance is not an autonomous feature of the gene, or its product, but it depends on the production of a particular phenotype from the gene product. n n n n n n It has many types of hereditary variation, which can be easily seen through low power microscope. Linkage and Recombination Å Å Morgan and his group observed in Drosophila that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental type. They attributed this due to physical association of the two genes and coined the term ‘linkage’ to describe this physical association of genes on a chromosome and the term ‘recombination’ to describe the generation of non-parental gene combinations. NEET Sex-Determination Å The establishment of sex through differential development in an individual at the time of zygote formation is called sex-determination. Å Henking in 1891, could trace a specific nuclear structure all through spermatogenesis in few insects. He observed that 50% of sperms received this specific structure after spermatogenesis, whereas the other 50% of sperms did not receive it. He named this structure as X-body. KEY NOTES www.mediit.in 95 CHAPTER 05 > Principles of Inheritance and Variation Scientists further explained that X-body was a chromosome and called it as X-chromosome. Å Å The chromosomal theory of sex-determination was worked out by EB Wilson and Stevens (1902-1905). They named XY-chromosomes as allosome or sex chromosomes and other chromosomes, which have no relation with the sex and contain genes, which determine the somatic characters as autosomes (AA). Å The mutations are of following types Mutation Gene mutations Point mutation Thus, on the basis of the type of allosome present in the gamete, the parents can be of two types Homogametic, i.e. producing similar gametes. Frameshift mutation Chromosomal mutations Structural variation aberrations Aneuploidy Numerical variations Polyploidy n n Å Heterogametic, i.e. producing different gametes. Sex-determination pattern in different organisms is as follows Types of sexdetermination mechanism Features Examples XX-XY method Females are homogametic as all the chromosomes bear only X-chromosome. Males are heterogametic as half of the gametes have X-chromosomes and the other half bears Y-chromosomes. Humans, Drosophila, etc. Females are homogametic as all gametes bear only X-chromosome. Males are heterogametic as half of the gametes bear X-chromosome and the other half does not have any sex-chromosome. Roundworms, insects, etc. ZW-ZZ method Females are heterogametic half of the gametes have Z-chromosome and the other half have W-chromosome. Males are homogametic as all the gametes possess only Z-chromosome. Fishes, reptiles etc. ZO-ZZ method Females are heterogametic as half of the gametes have Z-chromosome and the other half has no chromosome. Males are homogametic and all the gametes bear only Z-chromosome. Moths, butterflies, etc. Unfertilised egg produces a haploid male. Fertilised egg produces a diploid gamete. Honeybees, etc. XX-XO method Monosomy Å Å Å Å Trisomy Autopolyploidy Allopolyploidy Mutation occurring due to change in a single base pair of DNA. This is called point mutation, e.g. sickle-cell anaemia. Deletions and insertions of base pairs of DNA cause frameshift mutation. The loss or gain of a segment of DNA, results in structural alteration in chromosomes because genes are located on the chromosomes. This alteration in chromosomes results in abnormalities and is common in cancerous cells. When members of a homologous pair of chromosomes fail to segregate during meiosis, aneuploidy occurs. It means, there is loss or gain of one or more chromosomes. Monosomy, i.e. lack of one chromosome of normal complement. Trisomy, i.e. three instead of normal two chromosomes. n n Å Polyploidy occurs when there is failure of cytokinesis after telophase stage of cell division resulting in an increase in a whole set of chromosomes in an organism. In this phenomenon, the cell has loss or gain of three, four or more sets of chromosomes. Autopolyploids are polyploids with multiple chromosome sets derived from a single species. Allopolyploids where chromosomes are derived from different species, i.e. result of multiplying the chromosome number and forming a hybrid. n Haplodiploidy n Mutation Å Å It is a sudden, stable and inheritable change in genetic material or DNA sequences of an organism. The organism, which undergoes mutation is called mutant. The chemical and physical factors that induce mutations are called mutagens, e.g. UV radiations, etc. Pedigree Analysis Å Å The analysis of traits in several generations of a human family in the form of a family tree or diagram is called pedigree analysis. It serves as a strong tool, which is utilised to trace the inheritance of a specific trait, abnormality or disease. Inheritance pattern of traits in human beings cannot be studied by crosses as in case of other organisms due to following reasons The progeny produced is very small (usually one) and therefore, takes long time. Controlled crosses cannot be performed. n n NEET KEY NOTES www.mediit.in Master The NCERT > Biology (Vol-II ) 96 The symbols used in pedigree analysis are given below Å Various Mendelian disorders are tabulated below Male Disorders Characteristics Female Colour blindness Sex unspecified Affected individual Mating Haemophilia Heterozygous or Carrier male Heterozygous or Carrier female Mating between relatives (consanguineous mating) Sickle-cell anaemia Parents above and children below (in order of birth-left to right) Phenylketonuria Parents with male child affected with disease Thalassemia Dizygous twins Monozygous twins 5 Five unaffected offspring Sex-linked recessive disorder caused due to mutation in genes present on X-chromosome. Mostly females are carrier while males contract the disease. Affected person fails to discriminate red and green colour. Sex-linked recessive disorder which prevent clotting of blood. Heterozygote females are carrier who transmit the disease to sons. Autosome linked recessive trait. Caused due to the substitution of glutamic acid by valine as the sixth codon of β-globin gene gets substituted from GAG to GUG. RBCs become sickle-shaped under low O2 tension. Autosomal recessive trait. Individual lack enzyme that convert phenylalanine into tyrosine leading to accumulation of phenylpyruvic acid in body, brain, etc. Autosome linked recessive trait. α-thalassemia is caused due to the mutation in HBA1 and HBA2 genes on chromosome 16. β-thalassemia is caused due to the mutation in HBB gene on chromosome 11. The rate of synthesis of α or β-chain gets reduced leading to the formation of abnormal haemoglobin. Symbols used in the human pedigree analysis Genetic Disorders Å Å Chromosomal Disorders Å These are disorders or illness which caused by one or more abnormalities in the autosomes or sex chromosomes of the person. Thus, referred to as autosomal disorders or sex-linked disorders, respectively. n The genetic disorders are divided into n Genetic Disorders Å Mendelian Disorders e.g. Haemophilia, cystic fibrosis, colour blindness, Sickle-cell anaemia, thalassemia, phenylketonuria, etc. Chromosomal Disorders e.g. Down’s syndrome, Turner’s syndrome, Klinefelter’s syndrome, etc. Mendelian Disorders Å It caused due to excess, the absence or abnormal arrangement of one or more chromosomes. These are of two types as follows Autosomal abnormality or disorder, e.g. Down’s syndrome (Mongolian idiocy). Sex chromosome abnormality, e.g. Klinefelter’s syndrome and Turner’s syndrome. Various chromosomal disorders are tabulated below Disorders Down’s syndrome Sex-linked recessive disorder, e.g. colour blindness and haemophilia. Klinefelter’s syndrome It caused due to alteration or mutation in a single gene. These are of two types n Characteristics Turner’s syndrome n Autosomal recessive disorder, e.g. thalassemia, phenylketonuria and sickle-cell anaemia. NEET 21 trisomy (described by Langdon Down) Cause short statured, furrowed tongue, small round head, palm crease, retarded mental development and physical appearance. Presence of an additional X-chromosome (XXY). Cause sterility, gynaecomastia, overall masuline development, etc. Absence of one X-chromosome (XO). Sterile females, rudimentary ovaries, lack of secondary sexual characters. KEY NOTES www.mediit.in 97 CHAPTER 05 > Principles of Inheritance and Variation Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Mendel's Laws of Inheritance 1 Genetics is the branch of biology which deals with (a) variation (c) Both (a) and (b) 8 How many pairs of true breeding varieties were selected by Mendel for his experiment on pea plant? (b) inheritance (d) study of characters 2 The inheritance of characters from parents to (a) 12 (a) (b) (c) (d) is called considered by Mendel in his experiments on pea? (a) (b) (c) (d) (b) Lathyrus odoratus (d) Mirabilis jalapa 5 Which one from those given below is the period of Mendel’s hybridisation experiments? (a) 1856-1863 (c) 1857-1869 NEET 2017 (a) (b) (c) (d) manifested in two traits which were 7 A true breeding line is characterised by the presence of (a) stable trait inheritance due to the continuous selfpollination (b) varying traits in different generations due to the cross pollination (c) single trait in all generations due to allogamy (d) varying trait inheritance in a single generation due to geitonogamy NEET 2017 his experiment on pea plant? (b) 1840-1850 (d) 1870-1877 (b) non-zygote (d) opposite Stem – Tall or Dwarf Trichomes – Glandular or Non-glandular Seed – Green or Yellow Pod – Inflated or Constricted 11 Which is correct about traits choosen by Mendel for 6 Mendel investigated characters in garden pea plant (a) similar (c) identical 7 and 7 8 and 6 6 and 8 5 and 9 10 Among the following characters, which one was not (b) heredity (d) resemblance 4 Mendel’s hybridisation experimental material was (a) Pisum sativum (c) Oryza sativa (d) 15 how many traits were dominant and recessive? (b) heredity (d) resemblance 3 The tendency of offspring to differ from their parents (a) variation (c) inheritance (c) 14 9 Out of 7 contrasting trait pairs selected by Mendel, offspring is (a) variation (c) inheritance (b) 13 Terminal pod was dominant Constricted pod was dominant Green coloured pod was dominant Tall plants were recessive 12 What contributed to Mendel’s success? I. Selection of pureline pea varieties. II. Knowledge of history. III. Selecting one character at a time. IV. Statistical analysis and mathematical logic. Choose the correct option. (a) I, II, III and IV (c) I, III and IV (b) II and III (d) II, III and IV TOPIC 2 ~ Inheritance of One Gene 13 The first hybrid progeny obtained by Mendel were called (a) F1 -progeny (c) F 2 -progeny (b) F 0 -progeny (d) F 3 -progeny 14 F1 -progeny of a cross between pure tall and dwarf plant is always (a) (b) (c) (d) tall short intermediate None of these 15 According to Mendel’s observation, which generation of progeny always represents the phenotype of the dominant parent? (a) F4 (b) F2 (c) F1 (d) F0 16 The Mendel crossed true breeding tall and dwarf plant varieties in his experiment. Tallness was the dominant character and dwarfness was recessive. The recessive character appeared in (a) F1 (c) F3 (b) F 2 (d) F2 and F 3 www.mediit.in Master The NCERT > Biology (Vol-II ) 98 17 How did Mendel obtained recessive (dwarf) character in F2 -generation? (a) By self-pollinating F1 (b) By self-pollinating F2 (c) By cross-pollinating F1 (d) By cross-pollinating F2 18 The proportion of plants that were dwarf and tall, respectively in F2 -generation of Mendel’s experiment was 1 th and 4 2 (c) rd and 3 (a) 3 th 4 1 rd 3 3 th and 4 1 (d) rd and 3 (b) 1 th 4 4 rd 3 19 Mendel crossed tall and dwarf plants. In F2 -generation both the tall and dwarf plants were produced. This shows (a) (b) (c) (d) blending of characters atavism non-blending of characters intermediate characters 20 During his experiments, Mendel used the term factor for (a) genes (c) characters (b) traits (d) qualities 21 Genes which codes for a pair of contrasting characters are (a) recessive character (c) alleles (b) dominant character (d) alternative gene 22 Choose the incorrect match. (a) Phenotype – Physical appearance of an organism (b) Genotype – Expressed genes (c) Homozygous – Identical alleles of a gene present at the same locus (d) Heterozygous – Genes of an allelic pair are not same 23 Number of gametes produced by a homozygous and a heterozygous individuals of genotype AA and Aa, respectively are (a) 1 and 2 (c) 3 and 5 (b) 2 and 3 (d) many 24 A cross in which parents differ in a single pair of contrasting character is called (a) monohybrid cross (c) trihybrid cross (b) dihybrid cross (d) tetrahybrid cross 25 The phenotypic ratio of a monohybrid cross in F2 -generation is (a) 3 : 1 (c) 2 : 1 : 1 (b) 1 : 2 : 1 (d) 9 : 3 : 3 : 1 26 The genotypic ratio of a monohybrid cross in F2 -generation is (a) 3 : 1 (c) 2 : 1 : 1 (b) 1 : 2 : 1 (d) 9 : 3 : 3 : 1 27 F2 -generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as 1 : 2 : 1. It represents a case of CBSE-AIPMT 2012 (a) codominance (b) dihybrid cross (c) monohybrid cross with complete dominance (d) monohybrid cross with incomplete dominance 28 If the male plant has the genotype TT and the female plant has the genotype tt then they contribute pollen and egg, respectively with (a) T and T gametes (c) TT and tt gametes (b) tt and TT gametes (d) T and t gametes 29 Graphical representation to calculate the probability of all possible genotype of an offspring in genetic cross is called (a) Bunett square (c) Punnett square (b) Morgan square (d) Mendel square 30 Test cross involves a cross between (a) (b) (c) (d) recessive F1 -plant and dominant F2 -plant recessive F2 -plant and dominant F3 -plant dominant F2 -plant and recessive parent plants dominant F2 -plant and heterozygous parent plants 31 Mendel performed test cross to know the (a) genotype of F1 (c) genotype of F 3 (b) genotype of F 2 (d) genotype of F 4 32 When alleles of two contrasting characters are present together and one of the character expresses itself during the cross while the other remains hidden gives the (a) (b) (c) (d) law of purity of gametes law of segregation law of dominance law of independent assortment 33 The allele which expresses itself in both homozygous and heterozygous condition is called (a) (b) (c) (d) dominant allele recessive allele incomplete dominant allele split allele 34 3:1 ratio in F2 -generation is explained by (a) (b) (c) (d) law of partial dominance law of dominance law of incomplete dominance law of purity of gametes 35 The law of dominance is applicable in inheritance of (a) (b) (c) (d) seed colour in pea flower colour in Mirabilis jalapa starch grain size in pea roan coat colour in cattles www.mediit.in 99 CHAPTER 05 > Principles of Inheritance and Variation 36 Mendel’s principle of segregation means that the germ cells always receive (a) (b) (c) (d) one pair to alleles one quarter of the genes either one allele of father or one allele of mother any pair of alleles 37 The law based on fact that the characters do not show any blending and both the characters are recovered as such in F2 -generation although one character was absent in F1 -progeny, is (a) (b) (c) (d) law of purity of gametes law of independent assortment law of incomplete dominance law of dominance 38 Mendel crossed tall and dwarf plant. In F2 -generation the observed ratio was 3:1 (tall : short). From this result, he deduced I. law of dominance. II. law of independent assortment. III. law of segregation. IV. incomplete dominance. Choose the correct option. (a) I, II, III and IV (c) II, III and IV (b) I and III (d) I, II and III 39 Correctly select the genotype and phenotype of F1 -generation (R = dominant and red, r = recessive and white) from the given cross in plant snapdragon showing incomplete dominance. 42 TtRr represents (heterozygous tall, heterozygous pink). If this plant is self crossed then (T–dominant, t–recessive, R–dominant, r–recessive) I. 25% plants have red flowers. II. 25% plants have white flowers. III. 50% plants have pink flowers. IV. 50% plants are tall. Choose the correct option. (a) I and II (c) II, III and IV (b) I, II and III (d) I, II, III and IV 43 Which Mendelian idea is depicted by a cross in which the F1 -generation resembles both the parents? NEET 2013 (a) Incomplete dominance (b) Law of dominance (c) Inheritance of one gene (d) Codominance 44 What will be the ratio of offspring in a cross between the red coloured and pink coloured flowers of Mirabilis jalapa. (a) Red : Pink = 1 : 1 (c) Red : Pink = 1 : 3 (b) Red : Pink = 3 : 1 (d) Red : Pink = 2 : 3 45 The recessive trait in case of incomplete dominance is seen due to the (a) non-functional enzyme produced by modified gene (b) absence of any enzyme that may otherwise be produced by modified gene (c) normal or less efficient enzyme produced by recessive allele (d) Both (a) and (b) 46 The ABO blood groups are controlled by RR rr P-generation R r Gametes F1-generation (a) Rr and white (c) Rr and pink (b) Rr and red (d) cannot predict 40 Theoretically in incomplete dominance one allele functions as normal, while another allele may function as (a) (b) (c) (d) normal allele non-functional allele normal but less efficient allele All of the above 41 Incomplete dominance is similar to codominance in having identical (a) (b) (c) (d) phenotypic ratio genotypic ratio Both (a) and (b) None of the above (a) I-gene (c) B-gene (b) c-gene (d) n-gene 47 Out of the three alleles of gene I, the sugar polymers on the plasma membrane of RBCs is controlled by how many alleles? (a) All three (c) One (b) Two (d) O 48 In human blood group inheritance (a) (b) (c) (d) IA and IB are codominant IA and IB are dominant over i IA is dominant over IB Both (a) and (b) 49 If two persons with ‘AB’ blood group marry and have sufficiently large number of children, these children could be classified as ‘A’ blood group : ‘AB’ blood group : ‘B’ blood group in 1 : 2 : 1 ratio. Modern technique of protein electrophoresis reveals presence of both ‘A’ and ‘B’ type proteins in ‘AB’ blood group NEET 2013 individuals. This is an example of (a) codominance (c) partial dominance (b) incomplete dominance (d) complete dominance www.mediit.in Master The NCERT > Biology (Vol-II ) 100 50 In a marriage between male with blood group A and female with blood group B, the progeny had either blood group AB or B. What could be the possible genotype of parents? NEET (Odisha) 2019 (a) (b) (c) (d) IA i (Male) : IBIB (Female) IA IA (Male) : IBIB (Female) IA IA (Male) : IBi (Female) IA i (Male) : IBi (Female) (b) I, II and III (d) I, III and V 54 When there are more than two alleles controlling the mother is ‘B’. Then predict the blood group of the AIIMS 2019 progeny. A, AB A, B, AB, O B, AB O, A, B same character. These are called (a) pleiotropy (c) multiple alleles (b) polyalleles (d) All of these 55 Which of the following option (s) is/are correct for starch synthesis in pea seeds controlled by single gene which has two allelic forms B and b? 52 The genotypes of a husband and wife are I A I B and I A i. Among the blood types of their children, how many different genotypes and phenotypes are possible? NEET 2017 (a) (b) (c) (d) Dominance Codominance Multiple allele Incomplete dominance Polygenic inheritance (a) I, IV and V (c) II, III and V 51 Blood group of the father is ‘A’ and blood group of (a) (b) (c) (d) I. II. III. IV. V. 3 genotypes; 3 phenotypes 3 genotypes; 4 phenotypes 4 genotypes; 3 phenotypes 4 genotypes; 4 phenotypes (a) (b) (c) (d) BB is round seed with large starch synthesis bb is wrinkled seed with large starch synthesis Bb is round seed with less starch synthesis All of the above 56 Starch synthesis gene in pea plant in heterozygous condition produces starch grain of intermediate size. This shows 53 Which of the following characteristics represents ‘Inheritance of blood groups’ in humans? NEET 2018 (a) (b) (c) (d) complete dominance incomplete dominance codominance None of the above TOPIC 3 ~ Inheritance of Two Genes 57 The types of gametes formed by the genotype RrYy are (a) RY, Ry, rY, ry (c) Ry, Ry, Yy, ry (b) RY, Ry, ry, ry (d) Rr, RR, Yy, YY 58 In law of independent assortment how many factors are involved (for a dihybrid cross) (a) 2 (b) 3 (c) 4 shape (RR) was dominant over wrinkled seeds (rr) and yellow colour (YY) was dominant over green colour (yy). What are the expected phenotypes in the F1 -generation of the cross RRYY × rryy? Only round seeds with yellow cotyledons Only wrinkled seeds with yellow cotyledons Only wrinkled seeds with green cotyledons Round seeds with yellow cotyledons and wrinkled seeds with yellow cotyledons 60 In cross between pure breeding pea plants having yellow round (YYRR) and green wrinkled (yyrr) seeds, find out the total seeds (plants) having yellow colour in F2 -generation. (a) 12 (c) 14 (b) 10 (d) 11 (YYRR) and green wrinkled (yyrr) seeds, what will be the ratio between seeds having yellow and green seed colour? (a) 3 : 2 (b) 3 : 1 (c) 9 : 7 (d) 7 : 9 62 Total number of round seed in the F2 -generation of a (d) 1 59 In Mendel’s experiments with garden pea, round seed (a) (b) (c) (d) 61 In a cross between plants having yellow round cross between plants having pure yellow round and pure green wrinkled seeds is (a) 9 (b) 12 (c) 11 (d) 1 63 Ratio observed in dihybrid cross (phenotypically) (a) 3 : 1 (c) 9 : 7 (b) 1 : 2 : 1 (d) 9 : 3 : 3 : 1 64 The number of different genotypes observed in the F2 -generation of a dihybrid cross are (a) 9 (b) 12 (c) 4 (d) 6 65 Mendel’s result on inheritance of characters were rediscovered by (a) de Vries (c) von Tschermak (b) Correns (d) All of these 66 The literal meaning of chromosome is (a) painted body (c) doubling body (b) coloured body (d) thread-like body www.mediit.in 101 CHAPTER 05 > Principles of Inheritance and Variation 67 The concept of chromosome movement during meiosis to explain Mendel’s laws was used by (a) (b) (c) (d) Sutton and Boveri Malthus Correns Morgan 68 The chromosomes as well as genes occur in pair and the two alleles of a gene pair are located on (a) (b) (c) (d) homologous chromosomes non-homologous chromosomes single chromosome All of the above 69 Who proposed the chromosomal theory of inheritance? (a) (b) (c) (d) Sutton and Mendel Boveri and Morgan Morgan and Mendel Sutton and Boveri 70 Experimental evidences of chromosomal theory of inheritance was given by (a) S Boveri (c) de Vries Drosophila melanogaster Mangifera indica Mirabilis jalapa Drosophila indica whether dominant or recessive are transmitted from generation to generation in changed form unaltered form altered form disintegrated form present on (a) (b) (c) (d) X-chromosome different chromosome heterologous chromosome paired chromosome 76 Strength of the linkage between the two genes is (a) (b) (c) (d) proportionate to the distance between them inversely proportionate to the distance between them depend on the chromosomes depend upon the size of chromosomes (a) (b) (c) (d) 50% each 72% and 8.3%, respectively 0.3% and 53%, respectively 1.3% and 37.2%, respectively 78 In a test cross involving F1 dihybrid flies, more parental-type offspring were produced than the recombinant type offspring. This indicates NEET 2016 73 The figure depicts. Possibility I 75 Linked genes that were observed by Morgan were were linked tightly, while white and miniature wing were loosely linked. The per cent recombination shown by these genes were 72 Both chromosome and gene (Mendelian factors) (a) (b) (c) (d) (a) Sutton and Boveri – Chromosome theory (b) Walter and Boveri – Behaviour of chromosome during cell divisions (c) TH Morgan – Mutation (d) Henking – Barr bodies 77 In Morgan’s experiment, white and yellow genes (b) TH Morgan (d) W Sutton 71 Morgan’s experimental organism was (a) (b) (c) (d) 74 Choose the incorrect pairing among the following. Possibility II Two pair of homologous chromosomes (a) chromosomes failed to separate during meiosis (b) the two genes are linked and present on the same chromosome (c) Both of the characters are controlled by more than one gene (d) the genes are located on two different chromosomes 79 The frequency of recombination between gene pairs Anaphase-I (Meiosis-I) Anaphase-I (Meiosis-I) on the same chromosome as a measure of the distance between genes was explained by NEET (National) 2019 (a) Gregor J Mendel (c) Sutton-Boveri Anaphase-II (Meiosis-II) Anaphase-II (Meiosis-II) (b) Alfred Sturtevant (d) TH Morgan 80 What map unit (centi Morgan) is adopted in the construction of genetic maps? Germ cells (a) (b) (c) (d) Linkage Independent assortment Law of dominance Equational division Germ cells NEET (National) 2019 (a) A unit of distance between two expressed genes representing 100% cross over (b) A unit of distance between genes on chromosomes, representing 1% cross over (c) A unit of distance between genes on chromosomes, representing 50% cross over (d) A unit of distance between two expressed genes representing 10% cross over www.mediit.in Master The NCERT > Biology (Vol-II ) 102 81 Map units on linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons? (a) The relationship between recombination frequency and map units is different in every individual (b) Physical distances between genes change during the coures of cell cycle (c) Linkage map distances are identical between males and females (d) The frequency of crossing over varies along the length of the chromosome 82 Linkage group is (a) (b) (c) (d) linearly arranged group of linked gene non-linearly arranged group of linked gene non-linearly arranged group of unlinked gene non-linearly arranged group of single gene 83 Linkage groups are always present on the (a) homologous chromosomes (b) analogous chromosomes (c) sex chromosomes (d) heterologous chromosomes 84 Genetic maps can be used in human genome project (a) (b) (c) (d) starting point in the sequencing of whole genome measure the distance between genes map the position of genes on chromosomes All of the above 85 Genes A, B and C are linked. Genes A and B are more close than A and C. I. A might be before B and C. II. B might be between A and C. III. C might be between A and B. IV. More crosses cannot occur between A and C than A and B. Find out the correct option for the given information. (a) (b) (c) (d) I and II II and III III and IV I, II and IV TOPIC 4 ~ Polygenic Inheritance and Pleiotropy 86 Polygenic traits are controlled by (a) (b) (c) (d) one gene two genes three or more genes mutant genes 87 The polygenic traits (a) (b) (c) (d) are influenced by environment phenotype reflect the contribution of each allele effect of each allele is additive All of the above 88 In human skin colour which is a polygenic trait, all dominant and all recessive alleles show (a) (b) (c) (d) Darkest and lightest skin colour, respectively Lightest and darkest skin colour, respectively Only darkest skin colour Only lightest skin colour 89 In human skin colour inheritance, the genotype with three dominant and three recessive alleles will produce (a) darkest skin colour (b) lightest skin colour (c) intermediate skin colour (d) patches of black and white 90 A pleiotropic gene (a) is not found in humans (b) is a single gene which exhibit multiple phenotypic expressions (c) show effect on metabolic pathways, so as to produce various phenotypes (d) Both (b) and (c) 91 Phenylketonuria is caused due to (a) (b) (c) (d) pleiotropy multiple alleles codominance incomplete dominance 92 Phenylketonuria in human (a) (b) (c) (d) manifests through phenotypic expressions is characterised by mental retardation leads to hair reduction and skin pigmentation All of the above 93 Which one of the following pairs is wrongly matched? (a) (b) (c) (d) NEET 2018 XO type of sex-determination – Grasshopper ABO blood grouping – Codominance Starch synthesis in pea – Multiple allele TH Morgan – Linkage www.mediit.in 103 CHAPTER 05 > Principles of Inheritance and Variation TOPIC 5 ~ Sex-Determination 94 Sex-determination is controlled by … A… and the remaining chromosomes which are not involved in sex-determination are …B… . (a) (b) (c) (d) A Allosomes Allosomes Sex-chromosomes Autosomes B Autosomes Sex-chromosomes Allosomes Sex-chromosomes (c) Male Drosophila – Heterogametic (d) None of the above 99 The chromosomal denotation for heterogametic female and homogametic males are (a) ZW and ZZ (c) XX–XO 100 A human male contains the karyotype of … A… and a human female has …B… chromosomes. 95 Choose the incorrect pair with respect to sex determination in different organisms. (a) (b) (c) (d) Grasshopper Birds Drosophila Human = XO type = ZZ-ZW type = XX-XO type = XX-XY type 96 In XX and XY type of sex-determination, (a) (b) (c) (d) males are heterogametic females are isogametic Both (a) and (b) None of the option is correct 97 Male heterogamety is seen in (a) Humans (c) Drosophila (b) Grasshopper (d) All of these 98 Choose the incorrect pair amongst the following. (a) Male bird – Homogametic (b) Female bird – Heterogametic (b) ZO–ZZ (d) Both (a) and (b) (a) (b) (c) (d) A 44 + XX 44 + XY 44 + XO 44 + XX B 44 + XY 44 + XX 44 + XX 44 + XO 101 The number of chromosomes in females and males honeybees are (a) (b) (c) (d) 32 16 32 and 16, respectively 16 and 32, respectively 102 The unfertilised eggs in honeybees develop into (a) males (c) worker (b) queen (d) Both (a) and (c) 103 In honeybees, male and female gametes are produced through (a) mitosis (c) meiosis (b) mitosis and meiosis, respectively (d) meiosis and mitosis, respectively TOPIC 6 ~ Mutation 104 Mutation is a phenomena which results in alteration in sequences of (a) DNA (c) proteins (b) RNA (d) Both (a) and (b) (a) change in genotype (b) change in phenotype (c) change in metabolism (d) All of these 106 Chromosomal abberation is commonly found in the (b) normal cells (d) autosomal cells 107 Point mutation arises due to the change in (a) (b) (c) (d) Transition = 8, Transversion = 4 Transition = 4, Transversion = 4 Transition = 8, Transversion = 4 Transition = 4, Transversion = 8 109 Sickle-cell anaemia is a classical example of 105 Mutation may result in (a) cancer cells (c) healthy cells (a) (b) (c) (d) single base DNA single base pair of DNA segment of DNA double base pair of DNA 108 If there are four different types of nitrogenous bases (A, T, G and C) then how many different types of transitions and transversion are possible? (a) (b) (c) (d) frame-shift mutation point mutation Both (a) and (b) None of the above 110 Frame-shift mutation arises due to (a) (b) (c) (d) deletion of base pair of DNA insertion of base pair of DNA Both (a) and (b) change in single base pair of DNA 111 Mutagens are (a) (b) (c) (d) chemical agents which cause change in DNA physical agents which cause mutation Both (a) and (b) None of the abvoe www.mediit.in Master The NCERT > Biology (Vol-II ) 104 TOPIC 7 ~ Genetic Disorders 112 Analysis of traits of several generation of a family in the form of diagram is called (a) gene analysis (c) allele analysis (b) chromosome analysis (d) pedigree analysis 113 Pedigree analysis is very important in human beings because (a) (b) (c) (d) it helps genetic counselors to avoid disorders it shows origin of traits it shows the flow of traits in family All of the above (a) (b) (c) (d) character is carried by Y-chromosome character is sex-linked recessive character is sex-linked dominant character is recessive autosomal 118 In the following human pedigree, the filled symbols represent the affected individuals. Identify the type of given pedigree. 114 Identify the correct choice for given symbols (A and B). A (a) (b) (c) (d) B A–Consanguineous mating; B–Mating A–Mating; B–Mating between relatives A–Mating; B–Consanguineous mating Both (b) and (c) 115 Identify the symbols given below and the correct option with respect of A, B , C and D. A B C D (a) A–Male, B–Female, C–Sex unspecified, D–Affected male (b) A–Male, B–Female, C–Sterile, D–Carrier male (c) A–Male, B–Female, C–Fertile, D–Affected female (d) A–Female, B–Male, C–Sex unspecified, D–Carrier female (a) X-linked dominant (c) Autosomal dominant (b) Autosomal recessive (d) X-linked recessive 119 In a family, father had a trait but mother did not. All their sons and daughter had this trait. The same trait was found in some grand daughters, though daughter were married to the normal persons. Choose the correct pedigree chart for this condition. (a) 116 Identify the type of inheritance in the given diagram. (b) (c) (a) (b) (c) (d) Dominant X-linked Recessive X-linked Dominant Y-linked Cytoplasmic or Mitochondrial inheritance 117 Following pedigree chart shows (d) www.mediit.in 105 CHAPTER 05 > Principles of Inheritance and Variation 120 Observe the pedigree chart given below. Find out the 126 A man whose father was colourblind marries a woman, who had a colourblind mother and normal father. What percentage of male children of this CBSE-AIPMT 2014 couple will be colourblind ? cause of trait, i.e. it is due to (a) 25% (c) 50% (b) 0% (d) 75% 127 A normal woman whose father was colourblind, (a) (b) (c) (d) marries a normal man. What kinds of children can be AIIMS 2018 expected and in what proportion ? Incompletely dominant allele Dominant allele Either dominant or recessive allele Recessive allele 121 The diagram given below show the inheritance of haemophilia in a family. What will be the genotype of the individual marked M? (a) All daughters normal, 50% of sons colourblind (b) All daughters normal, all sons colourblind (c) 50% daughters colourblind, all sons normal (d) All daughters colourblind, all sons normal 128 Which of the following most appropriately describes haemophilia? (a) (b) (c) (d) M NEET 2016 X-linked recessive gene disorder Chromosomal disorder Dominant gene disorder Recessive gene disorder 129 In haemophilia, the affected protein is a part of a cascade of protein which is involved in the (a) M − XY (c) M − X h X h (b) M − XX (d) M − X h X 122 Given below is a pedigree chart of a family with five children. It shows the inheritance of attached ear lobes as opposed to the free ones. Which of the following condition can be drawn? (a) (b) (c) (d) Parents are heterozygous Parents are homozygous recessive Parents are homozygous dominant All are incorrect (a) (b) (c) (d) formation of RBCs formation of WBCs and platelets coagulation of blood anticoagulation 130 Sickle-cell anaemia is an autosomal linked recessive trait that can be transmitted from parents to the offspring when both the partners are carriers for all the genes or heterozygous. The disease is controlled by a single pair of allele, Hb A and HbS . Identify X, Y and Z. GAG Normal Hb (A) Gene 123 Colour blindness in humans mRNA (a) results in defect in either red or green cone of eyes (b) is caused due to the mutation in gene found on X-chromosome (c) affects males more frequently than females (d) All of the above GAG Val His Leu Thr Pro Glu Glu 1 2 3 4 5 6 7 HbA 124 A woman has an X-linked condition on one of her X-chromosomes. This chromosome can be inherited by Peptide Sickle-cell Hb (S) Gene NEET 2018 (a) Only grand children (c) Only daughters CTC X Y (b) Only sons (d) Both (b) and (c) mRNA Z 125 A normal-visioned man whose father was colourblind, marries a woman whose father was also colourblind. They have their first child as a daughter. What are the chances that this child would be colourblind? (a) 100% (c) 25% (b) 0% (d) 50% CBSE-AIPMT 2012 Val His Leu Thr Pro Val Glu 1 2 3 4 5 6 7 HbS Peptide www.mediit.in Master The NCERT > Biology (Vol-II ) 106 X (a) GTG (b) CAC (c) GTA (d) GTC Y CAC CTC GAG GAC Z Val (GUG) Val (GUG) Val (GUG) Val (GUG) 139 A disease caused by an autosomal primary non-disjunction is (a) Down’s syndrome (c) Turner’s syndrome 140 Karyotype of Down’s syndrome has how many 131 In sickle-cell anaemia, chromosomes? (a) Both parents are heterozygous carriers, but are unaffected (b) Single pair of allele controls the disease (c) Only Hb s Hb s show diseased phenotype (d) All of the above 132 In individual suffering from phenylketonuria, (a) (b) (c) (d) enzyme phenylalanine hydroxylase is absent phenylalanine do not convert to tyrosine phenylpyruvic acid is formed All of the above 133 Thalassemia in humans (a) is an autosome linked recessive blood disorder (b) can transmit from parents to offspring when both parents are unaffected carriers (heterozygous) (c) caused due to the mutation or deletion of one of the α or β-globin chain (d) All of the above 134 α-thalassemia in humans is controlled by (a) HBA1 and HBA2 genes on chromosome 16 (b) HBA1 gene on chromosome 12 (c) HBA2 gene on chromosome 11 (d) HBA1 and HBA2 genes on chromosome 9 (a) 43 141 I. II. III. IV. (b) 46 Short statured body with small round head. Furrowed tongue and partially opened mouth. Palm is broad with characteristic palm crease. Slow physical, psycomotor and mental development. These are the characters of (a) Down’s syndrome (b) Turner’s syndrome (c) Klinefelter’s syndrome (d) Edward syndrome 142 Choose the correct pair. (a) Gynacoemastia – Development of breasts (b) Turner’s syndrome – Loss of an X-chromosome in females (c) Polyploidy – Seen in plants (d) All of the above 143 What is the genetic disorder in which an individual has an overall masculine development gynaecomastia and is sterile? NEET (National) 2019 (a) (b) (c) (d) XX egg and Y from sperm XX egg and XY sperm X egg and XY sperm Both (a) and (c) 145 In which genetic condition, each cell in the affected person, has three sex chromosomes XXY? NEET (Odisha) 2019 136 Failure of segregation of chromatid during cell (a) Thalassemia (c) Phenylketonuria division cycle results in the gain or loss of chromosome which as called (b) hypopolyploidy (d) polyploidy plant brought from the field. He tells his teacher that this cell is not like other cells at telophase stage. There is no formation of cell plate and thus the cell is containing more number of chromosomes as compared to other dividing cells. This would result in NEET 2016 polyploidy somaclonal variation polyteny aneuploidy (a) trisomy (c) gene mutation JIPMER 2018 (b) normal diploid (d) None of these (b) Klinefelter’s syndrome (d) Turner’s syndrome 146 Monosomy and trisomy are represented respectively as 137 A cell telophase stage is observed by a student in a 138 Non-disjunction in meiosis results in (d) 45 144 Klinefelter’s syndrome results from (a) HBA2 gene on chromosome 16 (b) HBB gene on chromosome 11 (c) HBA1 gene on chromosome 15 (d) HBA1 and HBA2 gene on chromosome 8 (a) (b) (c) (d) JIPMER 2019 (c) 47 (a) Klinefelter’s syndrome (b) Edward syndrome (c) Down’s syndrome (d) Turner’s syndrome 135 β-thalassemia in humans is controlled by (a) aneuploidy (c) hyperpolyploidy NEET 2017 (b) Klinefelter’s syndrome (d) Sickle-cell anaemia (a) n − 1, n + 2 (c) 2n − 1, 2n + 1 (b) 2n + 2, 2n + 1 (d) 2n − 2, 2n + 1 147 Female suffering from Turner’s syndrome possess (a) 45 + XO (b) rudimentary ovaries (c) lack of secondary sexual characters (d) All of the above 148 Which of the following are chromosomal disorders. I. Colour blindness II. Down’s syndrome III. Phenylketonuria IV. Turner’s syndrome V. Thalassaemia (a) I, II and III (c) III, IV and V (b) II, IV and V (d) II and IV www.mediit.in 107 CHAPTER 05 > Principles of Inheritance and Variation NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Direction (Q. No. 149-163) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 149 Assertion (A) Offspring have characteristics of both 150 151 152 153 154 155 156 157 the parents. Reason (R) Characters pass from the parents to their progeny. Assertion (A) True breeding lines have stable trait inheritance for several generations. Reason (R) Mendel conducted cross-pollination experiments on true breeding lines. Assertion (A) In F2 -generation, the traits seen in the progeny were identical to their parents. Reason (R) The progeny of the F2 -generation show no blending of traits. Assertion (A) Genes are not passed on from one generation to the next. Reason (R) Genes serves as the units of inheritance. Assertion (A) Gametes receives only one allele of a gene. Reason (R) Mitosis occurs during gamete formation leading to the formation of haploid gametes. Assertion (A) In codominance, the F1 -generation resembles both the parents. Reason (R) An example is different type of red blood cells that determine ABO blood grouping in humans. Assertion (A) Behaviour of chromosome is parallel to gene. Reason (R) Genes are located on the chromosome. Assertion (A) Some genes tend to pass together from one generation to another. Reason (R) Such genes are located for away from each other on a chromosome. Assertion (A) Insects show female heterogamety. Reason (R) In insects, males have XO sex chromosome and females have XX sex chromosome. 158 Assertion (A) The mechanism of sex-determination in honeybee is called haplodiploidy. Reason (R) Female honeybees are haploid while male honeybees are diploid. 159 Assertion (A) The non-allelic genes for red hair and prickles are usually inherited together. AIIMS 2018 Reason (R) The genes for red hair and prickles are located on the same chromosome in close association. 160 Assertion (A) Down’s syndrome, Klinefelter’s syndrome and Turner’s syndrome are chromosomal disorders. Reason (R) In Klinefelter’s syndrome females are AIIMS 2019 sterile. 161 Assertion (A) Phenylketonuria is recessive hereditary disease caused by body’s failure to oxidise an amino acid phenylalanine to tyrosine, because of defective enzyme. AIIMS 2018 Reason (R) It is characterised by in the presence of phenylalanine acid in urine. 162 Assertion (A) Sickle-cell anaemia is an autosome linked recessive trait. Reason (R) It is controlled by a single pair of allele. 163 Assertion (A) Down’s syndrome is a Mendelian disorder. Reason (R) It is caused due to the presence of an additional copy of chromosome 21. II. Statement Based Questions 164 Which of the following statement is not true for two genes that show 50% recombination frequency? NEET 2013 (a) The genes may be on different chromosomes (b) The genes are tightly linked (c) The genes show independent assortment (d) If the genes are present on the same chromosome, they undergo more than one cross overs in every meiosis 165 In Antirrhinum (Snapdragon), a red flower was crossed with a white flower and in F1 -generation, pink flowers were obtained. When pink flowers were selfed, the F2 -generation showed white, red and pink flowers. Choose the incorrect statement from the following. NEET (National) 2019 www.mediit.in Master The NCERT > Biology (Vol-II ) 108 (a) Pink colour in F1 is due to incomplete dominance 1 2 1 (b) Ratio of F 2 is (Red) : (Pink) : (White) 4 4 4 (c) Law of segregation does not apply in this experiment (d) This experiment does not follow the principle of dominance 166 Select the incorrect statement. NEET (National) 2019 (a) In male grasshoppers, 50% of sperms have no sex-chromosome (b) In domesticated fowls, sex of progeny depends on the type of sperm rather than egg (c) Human males have one of their sex-chromosomes much shorter than the other (d) Male fruitfly is heterogametic 167 Which one of the following conditions correctly describes the manner of determining the sex? AIIMS 2018 (a) Homozygous sex chromosomes (ZZ) determine female sex in birds (b) XO type of sex chromosomes determine male sex in grasshopper (c) XO condition in humans as found in Turner’s syndrome determines female sex (d) Homozygous sex-chromosomes (XX) produce males in Drosophila 168 The following statements are regarding sex- determination. Choose the incorrect one. (a) There are two types of sex-determining mechanism (b) In male heterogamety, male has autosomes and sex chromosome XY (c) In female heterogamety, it has autosomes and one Z and one W chromosomes (d) Female heterogamety is found in mammals 169 Which of the following statement is incorrect? (a) X-body of Henking was given the name X-chromosomes (b) In many insects, all eggs bear an additional X-chromosomes besides autosomes (c) X-chromosomes is a sex chromosomes as it is involved in sex-determination (d) None of the above 170 Identify the incorrect statement for sex-determination in humans. (a) (b) (c) (d) Humans contain 23 pairs of autosomes Females produce only one type of ovum Genetic makeup of sperm determine the sex of the child In males, two types of gametes are produced 171 Which among the following statement is not true for haemophilia? (a) It is a sex-linked dominant disease (b) It is transmitted to unaffected carrier female to male progeny (c) The possibility of a female becoming a haemophilic is extremely rare (d) The family pedigree of Queen Victoria shows a number of haemophilic descendents 172 Thalassemia and sickle-cell anaemia are caused due to a problem in globin molecule synthesis. Select the correct statement. (a) Both are due to a qualitative defect in global chain synthesis (b) Both are due to a quantitative defect in globin chain synthesis (c) Thalassemia is due to the synthesis of abnormal haemoglobin molecules (d) None of the above 173 Select the incorrect statement. (a) RBCs become sickle-shaped under low oxygen tension in sickle-cell anaemia (b) Phenylpyruvic acid gets accumulated in brain and excreted in urine due to poor absorption by kidney (c) In thalassemia, α and β-globin chains are altogether absent in body (d) Thalassemia is an autosome linked recesive disease 174 Which of the following statement is correct with respect to monohybrid and dihybrid cross? (a) A monohybrid cross is performed for one generation whereas dihybrid cross is performed for two generations (b) A monohybrid cross involves a single parent, whereas a dihybrid cross involved two parents (c) A monohybrid cross produces a single progeny whereas a dihybrid cross produce two progenies (d) A monohybrid cross involves individuals with one heterozygous character, whereas a dihybrid corss involves individuals with two heterozygous characters 175 Which of the following statement(s) is/are correct with respect to the law of segregation? (a) Alleles do not show blending (b) The paired factors or alleles segregate from each other such that a gamete receives the two factors as in the original paired form (c) Homozygous parent produce similar types of gametes whereas heterozygous ones produce two types of gametes each having one allele with unequal proportion (d) All of the above 176 Which of the following statement(s) is/are true with respect to sickle-cell anaemia? (a) The mutant haemoglobin of sickle-cell anaemic individual undergo polymerisation under low oxygen tension causing sicking of RBCs (b) Sickle-cell anaemia occur due to the single base substitution (GAG → GUG) at the sixth codon of β-globin gene (c) Individuals heterozygous for sicke-cell anaemia ( Hb SHb A ) are resistant towards malaria (d) All of the above www.mediit.in 109 CHAPTER 05 > Principles of Inheritance and Variation 177 Which of the following statement is incorrect? (a) Mutations provide variations on which natural selection acts (b) The vast majority of mutations produce dominant alleles (c) Mutations arise spontaneously, infrequently and randomly (d) Rate of mutation can be increased by artificial means 178 Read the following statements. I. Mendelian factors are now called genes. II. Characters blend in homozygous condition only. III. All characters in human show dominance. IV. Hugo de Vries was involved in rediscovery of Mendel’s works. Which of the above statements are true? (a) I and II (c) I and IV (b) II and III (d) IV and III 179 Which of the following is true about linkage ? I. It is phenomenon in which more recombinants are produced in F2 -generation. II. More parental combinations are produced in F 2 -generation. III. Genotype which are present in F1 hybrid, reappear in high frequency in F2 -generation. IV. It is a phenomenon in which two chromosomes are linked. 182 Consider the following statements regarding ABO blood group in human. I. It is controlled by multiple alleles. II. It shows codominance. III. Codominance can be manifested phenotypically in human. IV. It follows the Mendel’s law of inheritance. Which of the statments(s) given above are correct? (a) Only I (c) II and III (b) I and II (d) IV and II 183 Consider the following statements. I. 100% parental combinations are found in F 2 -generation. II. F 2 phenotypic ratio is 3 : 1 in dihybrid cross. III. Dihybrid test cross ratio is 1 : 1 inF 2 -generation. IV. Linked genes tends to separate frequently. Which of the statement given above are correct? (a) I, II and IV (c) II, III and IV (b) I, III and IV (d) I and II 184 Select the incorrect statement(s) from the options Choose the correct option. given below with respect to dihybrid cross. AIIMS 2018 I. Tightly linked genes on the same chromosome show higher recombinations. II. Genes far apart on the same chromosome show very few recombinations. III. Genes loosely linked on the same chromosome show similar recombinations. (a) Only I (c) I and III (a) I and II (c) I and III (b) Only II (d) III and IV 180 Which of the following statements are false? I. A dominant allele determines the phenotype when paired with a recessive allele. II. A recessive allele is weaker than a dominant allele. III. A recessive allele do not shows its effects when paired with a dominant allele. IV. A dominant allele is always better for an organism. (a) II, I and IV (c) I, II and III (b) II, III and IV (d) I, III and IV 181 Which of the following statements are false? I. Specific mutations are acquired and occur only when required. II. Inheritance of specific trait can be determined using pedigree analysis. III. Like recombination, mutations cause variations in the DNA sequence. IV. Chromosomal aberrations are observed in cancer cells randomly irrespective of the alleles present. Choose the correct option. (a) II and III (c) II, III and IV (b) Only I (d) I, II and IV (b) III and II (d) All of these 185 Consider the following statements and select the statement(s) which are correct with respect to the reasons as to why Mendel could not find out about linkage? I. Some genes are linked, but they are too far apart for crossing over to be distinguished from independent assortment. II. Linked genes, were never tested for the same time in same cross. III. All seven genes, were present on the same chromosomes. IV. All seven genes were present on 4 chromosomes, but they were present far apart. (a) I and II (c) III and IV (b) II and III (d) Only IV 186 Consider the following statement and select the statements which are correct with respect to the reasons as to why Mendel’s work remain unrecognised for a long time. I. Communication was not easy. II. Concept of factors which did not blend was not accepted. www.mediit.in Master The NCERT > Biology (Vol-II ) 110 III. Use of mathematics to explain biological problem was unacceptable. IV He could not provide any physical proof for the existance of factors. (a) I and II (c) III and IV (b) II and III (d) All of these 187 Consider the following statements. I. Henking found specific nuclear structures through spermatogenesis in the 50% sperms of few insects. II. The sex-determination in honeybee is based on the number of sets of chromosomes an individual receives. Select the correct option. 188 Which of the following statements are correct reasons for why fruitfly is excellent model for genetics? I. Small life cycle (two week). II. Can be feed on simple synthetic medium. III. Single mating produce large number of progeny. IV. Clear differentiation of sexes. V. Many heredity variation can be seen with low power microscopes. Choose the correct option. (b) I, III and IV (d) I and IV III. Matching Type Questions Column I (Genetic crosses) Select the correct option. (b) I is false, II is true (d) Both I and II are false 190 Consider the following statements. I. The number of chromosomes in male and female insects is same. II. The female insects are heterozygous while male insect is homozygous. Column II (Phenotypic ratios) A. Test cross 1. 9:3:3:1 B. Monohybrid cross 2. 1:1 C. Dihybrid cross 3. 3:1 Codes A (a) 2 (c) 3 B 1 2 C 3 1 A (b) 2 (d) 1 B 3 3 C 1 2 194 Match the following columns. (b) III, IV and V (d) All of these 189 Consider the following statements. I. The crosses carried out by Morgan on Drosophila were sex-linked dihybrid crosses. II. The F2 -ratio in Morgan’s experiment deviated significantly from 9 : 3 : 3 : 1 ratio. (a) I is true, II is false (c) Both I and II are true (a) II and IV (c) I, II and III 193 Match the following columns. (a) Both I and II are true (b) I is true, II is false (c) Both I and II are false (d) I is false, II is true (a) I, II and III (c) I, IV and V 192 Pick out the correct statements. NEET 2016 I. Haemophilia is a sex-linked recessive disease. II. Down's syndrome is due to aneuploidy. III. Phenylketonuria is an autosomal recessive gene disorder. IV. Sickle-cell anaemia is an X - linked recessive gene disorder. Column I (Chromosomal abberation) AIIMS 2019 Column II (Features) A. Inversion 1. Change in linear order of genes by 180º rotation B. Duplication 2. Loss of part of chromosome C. Deletion 3. Addition of part of chromosome so that it is represented twice D. Translocation 4. Shifting of a part of chromosome to another non-homologous chromosome Codes A (a) 1 (c) 1 B 2 3 C 3 2 D 4 4 (b) (d) A 4 2 B 3 1 C 2 4 D 1 3 195 Match the following columns. Select the correct option. (a) I is true, II is false (c) I is false, II is true Column I (Genetic interactions) (b) Both I and II are true (d) Both I and II are false 191 Consider the following statements. I. Both colour blindness and haemophilia are sex-linked recessive traits. II. In sex-linked recessive traits, heterozygous or carrier female transmit disease to sons. Select the correct option. (a) Both I and II are true (b) I is true, II is false (c) Both I and II are false (d) I is false, II is true Column II (Genetic cross ratios) A. Incomplete dominance 1. 12 : 3 : 1 B. Dominant epistasis 2. 1:2:1 C. Recessive epistasis 3. 9:7 D. Complementary genes 4. 9:3:4 Codes A (a) 2 (c) 3 B 1 4 C 4 1 D 3 2 A (b) 1 (d) 4 B 2 3 C 3 2 D 4 1 www.mediit.in 111 CHAPTER 05 > Principles of Inheritance and Variation 199 Match the following columns. 196 Match the following columns. Column I (Scientists) Column I Column II (Discoveries) Column II A. Non-parental gene exchange 1. Crossing over Non-sister chromatids 2. X and Y A. Gregor Mendel 1. Chromosomal theory of inheritance B. C. Sex chromosome 3. Polyploidy B. Sutton and Boveri 2. Law of inheritance D. More than two sets of chromosomes 4. Recombination C. Henking 3. Linkage D. Morgan 4. Discovered X-body E. de Vries 5. Mutation Codes A (a) 4 (b) 2 (c) 4 (d) 2 B 2 1 1 3 C 1 4 5 4 D 3 3 3 5 Codes A (a) 4 (c) 2 D 3 1 A (b) 2 (d) 2 Column I Column II ABO blood groups 1. Dihybrid cross B. Law of segregation 2. Monohybrid cross C. Law of independent assortment 3. Base pairs substitution D. Gene mutation 4. Multiple allelism 1. Codominance. 2. Change in nucleotides C. Epistasis 3. One gene shows multiple phenotypic expression D. Mutation 4. Non-allelic gene inheritance Codes A (a) 1 (c) 3 B 2 1 C 3 4 D 4 2 (b) (d) A. Dominance 1. Many genes govern a single character B. Codominance 2. In a heterozygous organism only one allele expresses itself C. Pleiotropy 3. In a heterozygous organism both alleles express themselves fully D. Polygenic inheritance 4. A single gene influences many characters B 1 3 3 1 C 2 4 1 4 D 3 1 2 3 B 3 3 C 4 4 D 1 2 NEET (Odisha) 2019 Column II A. XX-XO method of sex-determination 1. Turner’s syndrome B. XX-XY method of sex-determination 2. Female heterogamety C. Karyotype-45 3. Grasshopper D. ZW-ZZ method of sexdetermination 4. Female homogamety NEET 2016 Column II (Description) A 2 1 201 Match the items of Column I with Column II. 198 Match the terms in Column I with their description in Column II and choose the correct option. AIIMS 2019 B. D 3 1 3 3 Column I (Terms) D 3 3 Both alleles express equally Column I C 4 4 2 1 C 4 1 Column II A. Pleiotropic gene A. B 1 3 1 2 B 1 4 option from the codes given below. Column I Codes A (a) 4 (b) 2 (c) 4 (d) 2 C 2 3 200 Match the following columns and choose the correct E 5 5 2 1 197 Match the following columns. Codes A (a) 2 (b) 2 (c) 4 (d) 4 B 1 4 Codes A (a) 2 (c) 3 B 4 4 C 1 1 D 3 2 A (b) 1 (d) 4 B 4 2 C 2 1 D 3 3 202 Match the following columns. Column II (Chromosome complement) A. Column I (Animals) Fruitfly 1. 2n = 6 + XY B. Fowl 2. 2n = 14 + XX C. Grasshopper 3. 2n = 16 + XO D. Human 4. 2n = 44 + XY Codes A (a) 1 (c) 3 B 2 4 C 3 1 D 4 2 A (b) 2 (d) 2 B 3 1 C 4 4 D 1 3 www.mediit.in Master The NCERT > Biology (Vol-II ) 112 203 Match the following columns. Column I (Pedigree symbols) A. 1. Column II (Refers to) Death B. 2. Five unaffected offspring C. 5 3. Sex unspecified D. 5 4. Female 5. Male E. Codes A (a) 1 (b) 1 (c) 1 (d) 5 B 2 2 2 4 C 5 4 3 3 D 4 3 4 2 E 3 5 5 1 204 Match the following columns. A. B. C. D. E. Column I (Types of polyploid) Monoploidy Monosomy Nulisomy Trisomy Tetrasomy 1. 2. 3. 4. 5. Column II (Chromosomes constitution) 2 n–1 2 n+1 2 n+2 2 n–2 n Codes A B C D E (a) 2 1 3 4 5 (b) 5 2 4 1 3 (c) 1 5 3 4 2 (d) 5 1 4 2 3 205 Match the following columns. Column I (Genetical trait) Column II (Name of disorders) A. Autosomal linked recessive trait 1. Down’s syndrome B. Sex-linked recessive disease 2. Phenylketonuria C. Inborn metabolic error linked to autosomal recessive trait 3. Haemophilia D. Additional 21st chromosome 4. Sickle-cell anaemia Codes A (a) 3 B 4 C 1 D 2 (b) 4 (c) 2 (d) 4 1 1 3 2 4 2 3 3 1 NCERT Exemplar MULTIPLE CHOICE QUESTIONS 206 Which of the following is/are Mendelian disorder? (a) Thalassemia (c) Phenylketonuria (b) Cystic fibrosis (d) All of these 207 All genes located on the same chromosome (a) form different groups depending upon their relative distance (b) form one linkage group (c) will not form any linkage group (d) form interactive groups that affect the phenotype 208 A cross between two tall plants resulted in offspring having few dwarf plants. What would be the genotypes of both the parents? (a) TT and Tt (b) Tt and Tt (c) TT and TT (d) Tt and tt 209 In a dihybrid cross, if you get 9 : 3 : 3 : 1 ratio it denotes that (a) the alleles of two genes are interacting with each other (b) it is a multigenic inheritance (c) it is a case of multiple allelism (d) the alleles of two genes are segregating independently 210 In the F2 -generation of a Mendelian dihybrid cross the number of phenotypes and genotypes are (a) phenotypes-4, genotypes-16 (b) phenotypes-9, genotypes-4 (c) phenotypes-4, genotypes-8 (d) phenotypes-4, genotypes-9 211 Two genes ‘A’ and ‘B’ are linked. In a dihybrid cross involving these two genes, the F1 heterozygote is crossed with homozygous recessive parental type (aa bb). What would be the ratio of offspring in the next generation? (a) 1 : 1 : 1 : 1 (b) 9 : 3 : 3 : 1 (c) 3 : 1 (d) 1 : 1 212 Mendel’s law of independent assortment holds good for genes situated on the (a) non-homologous chromosomes (b) homologous chromosomes (c) extra nuclear genetic element (d) same chromosome www.mediit.in 113 CHAPTER 05 > Principles of Inheritance and Variation 213 It is said that Mendel proposed that the factor controlling any character is discrete and independent. This proposition was based on the (a ) results of F3 -generation of a cross (b) observations that the offspring of a cross made between the plants having two contrasting characters shows only one character without any blending (c) self-pollination of F1 offsprings (d) cross-pollination of F1 -generation with recessive parent 214 Occasionally, a single gene may express more than one effect. The phenomenon is called (a) multiple allelism (b) mosaicism (c) pleiotropy (d) polygeny 215 Person having genotype I A I B would show the blood group as AB. This is because of (a) pleiotropy (b) codominance (c) segregation (d) incomplete dominance 216 Mother and father of a person with ‘O’ blood group have ‘A’ and ‘B’ blood group, respectively. What would be the genotype of both mother and father? (a) Mother is homozygous for ‘A’ blood group and father is heterozygous for ‘B’ (b) Mother is heterozygous for ‘A’ blood group and father is homozygous for ‘B’ (c) Both mother and father are heterozygous for ‘A’ and ‘B’ blood group, respectively (d) Both mother and father are homozygous for ‘A’ and ‘B’ blood group, respectively 217 Distance between the genes and percentage of recombination shows (a) a direct relationship (b) an inverse relationship (c) a parallel relationship (d) no relationship 218 ZZ/ZW type of sex-determination is seen in (a) platypus (b) snails (c) cockroach (d) peacock 219 In a certain taxon of insects some have 17 chromosomes and the others have 18 chromosomes. The 17 and 18 chromosome-bearing organisms are (a) males and females, respectively (b) females and males, respectively (c) all males (d) all females 220 The inheritance pattern of a gene over generations among humans is studied by the pedigree analysis. Character studied in the pedigree analysis is equivalent to (a) quantitative trait (b) Mendelian trait (c) polygenic trait (d) maternal trait 221 If a genetic disease is transferred from a phenotypically normal, but carrier female to only some of the male progeny, the disease is (a) autosomal dominant (b) autosomal recessive (c) sex-linked dominant (d) sex-linked recessive 222 In sickle-cell anaemia glutamic acid is replaced by valine. Which one of the following triplet codes for valine? (a) G G G (c) G A A (b) A A G (d) G U G 223 Conditions of a karyotype 2n ± 1 and 2n ± 2 are called (a) aneuploidy (b) polyploidy (c) allopolyploidy (d) monosomy www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 114 Answers Mastering NCERT with MCQs 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 (c) (c) (c) (b) (c) (b) (b) (a) (d) (a) (c) (c) (d) (d) (a) 2 12 22 32 42 52 62 72 82 92 102 112 122 132 142 (b) (c) (b) (c) (b) (c) (b) (b) (a) (d) (a) (d) (a) (d) (d) 3 13 23 33 43 53 63 73 83 93 103 113 123 133 143 (a) (a) (a) (a) (d) (b) (d) (b) (a) (c) (b) (d) (d) (d) (a) 4 14 24 34 44 54 64 74 84 94 104 114 124 134 144 (a) (a) (a) (b) (a) (c) (a) (c) (d) (a) (a) (d) (d) (a) (d) 5 15 25 35 45 55 65 75 85 95 105 115 125 135 145 (a) (c) (a) (a) (d) (a) (d) (a) (a) (c) (d) (a) (b) (b) (b) 6 16 26 36 46 56 66 76 86 96 106 116 126 136 146 (d) (b) (b) (c) (a) (b) (b) (b) (c) (a) (a) (d) (a) (a) (c) 7 17 27 37 47 57 67 77 87 97 107 117 127 137 147 (a) (a) (d) (a) (b) (a) (a) (d) (d) (d) (b) (a) (a) (a) (d) 8 18 28 38 48 58 68 78 88 98 108 118 128 138 148 (c) (a) (d) (b) (d) (a) (a) (b) (a) (d) (d) (b) (a) (a) (b) 9 19 29 39 49 59 69 79 89 99 109 119 129 139 (a) (c) (c) (c) (a) (a) (d) (b) (c) (d) (b) (a) (c) (a) 10 20 30 40 50 60 70 80 90 100 110 120 130 140 (b) (a) (c) (d) (a) (a) (b) (b) (d) (b) (c) (c) (a) (c) (d) (b) (c) (b) (c) (a) 153 163 173 183 193 203 (c) (d) (c) (d) (b) (d) 154 164 174 184 194 204 (a) (b) (d) (d) (c) (d) 155 165 175 185 195 205 (b) (c) (a) (a) (a) (d) 156 166 176 186 196 (c) (b) (d) (d) (b) 157 167 177 187 197 (d) (b) (b) (a) (d) 158 168 178 188 198 (c) (d) (c) (d) (b) NEET Special Types Questions 149 159 169 179 189 199 (a) (a) (d) (a) (c) (a) 150 160 170 180 190 200 (b) (c) (a) (b) (d) (c) 151 161 171 181 191 201 (a) (b) (a) (b) (a) (c) 152 162 172 182 192 202 NCERT Exemplar Questions 206 (d) 216 (c) 207 (b) 217 (a) 208 (b) 218 (d) 209 (d) 219 (a) 210 (d) 220 (b) 211 (d) 221 (d) 212 (b) 222 (d) 213 (b) 223 (a) 214 (c) 215 (b) Answers & Explanations Answers & Explanations 5 (a) Mendel performed his hybridisation experiment on Pisum sativum (garden pea) for 7 years between 1856-1863. 6 (d) Mendel investigated characters in the garden pea plant that were manifested as two opposite traits, e.g. tall or dwarf plants, yellow or green seeds. This allowed him to set up a basic framework of rules governing inheritance, which was expanded on by later scientists to account for all the diverse natural observations and the complexity inherent in them. 7 (a) A true breeding line is one that have undergone continuous self-pollination, shows stable trait inheritance and expression for several generations. 9 (a) Mendel selected 7 dominant traits and 7 recessive traits out of the total 14 traits or 7 opposing pairs of traits. The traits have been tabulated below Characters Dominant traits Recessive traits Seed shape Round Wrinkled Seed colour Yellow Green Flower colour Violet White Pod shape Inflated Constricted Pod colour Green Yellow Flower position Axial Terminal Stem height Tall Dwarf www.mediit.in 115 CHAPTER 05 > Principles of Inheritance and Variation These are formed when epidermal cells become glandular and hair like, called as trichomes. This character was not amongst the seven pairs of characters of the pea plant. Mendel selected for his hybridisation experiments. 19 (c) In Mendel’s experiment dominant and recessive traits were expressed or appeared separately. This shows that there was no mixing of characters, thus non-blending of character in F2 -generations is observed. 22 (b) Option (b) is incorrect and can be corrected as The genetic composition of an organism, with respect to one or more characters whether the gene is expressed or not is called genotype. 36 37 38 23 (a) The formula to calculate the number of gametes from a given genotype is 2n . Where, n = number of heterozygosity in the given genotype. Thus, number/types of gametes produced by a homozygous individual of genotype AA is 2(0) = 1 and by heterozygous individual of genotype Aa is 2(1) = 2. 40 27 (d) Monohybrid cross with incomplete dominance shows the same genotypic and phenotypic ratio, i.e. 1 : 2 : 1, as depicted by the cross given below AA Red aa White A a Parents 41 Aa Pink F1-generation a A Gametes Gametes 42 a Aa A a Pink A aa AA Red White Aa Pink F2-generation Genotypic ratio – 1 (AA) : 2 (Aa) : 1 (aa) Phenotypic ratio – 1 (Red) : 2 (Pink) : 1 (White) 28 (d) Since, both the male and female parents are homozygous with genotype TT and tt, respectively they will contribute only one type of gamete. The male will produce gamete (pollen) of type T and the female will produce a gamete (egg) of type t. 31 (b) Mendel performed test cross to know the genotype of F2 . Test cross involves a cross between dominant F2 plant with the homozygous recessive parent plant. The ratio of monohybrid test cross is 1 : 1 between Tt and tt. So, if the ratio of test cross comes as mentioned, then the F2 genotype is heterozygous tall and if it deviates from this, then the F2 genotype is homozygous tall. 34 (b) 3:1 ratio in F2 -generation can be explained by the law of dominance. It states that, only dominant allele shows its effect even in the heterozygous condition and masks the effect of recessive allele. In the given ratio, 3 represents the dominant phenotype, while 1 represents the recessive phenotype. (c) Mendel’s principle of segregation means that the germ cells (gametes) always receive either one allele of father or one allele of mother. The law of segregation states that, hereditary characters in the form of allele segregate from each other during the formation of gametes. Half of the gametes carry one allele and other half carry other allele for a character. (a) Law of purity of gametes states that the characters which were hidden or masked in F1 progeny get recovered in the progeny of F2 -generation. (b) Option (b) is correct as the ratio of 3 : 1 helped to deduce law of dominance and law of segregation. Whereas law of independent assortement was deduced by Mendel by performing dihybrid cross ( 9 : 3 : 3 : 1). Incomplete dominance was not deduced by Mendel. (d) In incomplete dominance, the two genes of an allelomorphic pair are not related as dominant or recessive but each of them express themselves partially. In this phenomenon, one allele may function normally and the other may either function normally, may be non-functional or may perform normally, but with less efficiency. This occurs due to some changes in the allele which modifies the information present in it. Thus, option (d) is correct. (c) Both codominance and incomplete dominance give an identical genotypic and phenotypic ratio of 1 : 2 : 1. Codominance and incomplete dominance differ in the fact that in codominance both the alleles are dominant and express themselves at the same time. But in incomplete dominance, the two alleles are neither dominant nor recessive to each other. (b) On self-crossing TtRr plant, the following cross is obtained Tt Rr (heterozygous tall and pink) ↓ (self-crossed) Tt Rr × Tt Rr Gametes TR Tr tR tr TR TTRR (Tall red) TTRr (Tall pink) TtRR (Tall red) TtRr (Tall pink) Tr TTRr TTrr (Tall pink) (Tall white) TtRr (Tall pink) Ttrr (Tall white) tR TtRR (Tall red) ttRR ttrR (Dwarf red) (Dwarf pink) tr TtRr Ttrr ttRr ttrr (Tall pink) (Tall white) (Dwarf pink) (Dwarf white) TtRr (Tall pink) Plants with pink flower = 8 = 50% Plants with red flower = 4 = 25% Plants with white flower = 4 = 25% Tall plants = 75% Dwarf plants = 25% 43 (d) Option (d) is correct as in codominance, both alleles of a pair express themselves fully in F1 -generation, so it resembles both the parents. Answers & Explanations 10 (b) Trichomes are the epidermal tissues structure. www.mediit.in 116 Master The NCERT > BIOLOGY (Vol-II ) 44 (a) The cross between red flowered and pink flowered l When only one parent is homozygous plants of Mirabilis jalapa is depicted below % & × RR Red Rr Pink R R & R % RR R Parents r r l Gametes F1 - generation Rr Thus, the ratio of offspring produce would be Red : Pink = 1 : 1 46 (a) The ABO blood groups are controlled by the I-gene, which has three alleles (IA , IB, i). 47 (b) The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by ‘I’ gene. It has three alleles IA , IB and i. Out of these only two alleles IA and IB produce a slightly different form of the sugar, while allele i does not produce any sugar. Because humans are diploid organisms, each person possesses any two of the three I gene alleles. IA and IB are completely dominant over i. 49 (a) AB blood group is characterised by the presence of Answers & Explanations l both antigen A and B, i.e. IA and IB over the surface of RBCs. Phenotype AB ↓ Genotype IA IB ↓ Antigen A + Antigen B Here, both alleles are able to express themselves forming antigens A and B. This is called as codominance, a phenomenon in which both the alleles in a heterozygote are expressed. 50 (a) The possible genotype of parents, male with blood group A and female with blood group B, having progeny with either blood group AB or B is I A i (male) : I BI B (female). It can be depicted by the cross given below B I i A I I B I AI B Blood group AB I Bi Blood group B I Bi Blood group B 51 (b) Since, it has not been specified whether the parents are homozygous or heterozygous for the alleles of gene I the possible genotype of + and parent could be I I I i Phenotype A B B or & A B B I i I I A B When both parents are homozygous % A A & Genotype I I I I Phenotype A B B B When both parents are heterozygous % & A B Genotype I i I i Phenotype A B Thus, when blood group of father is A and of mother is B, then the blood group of progeny will be A, B, AB and O. 52 (c) A cross between a husband and wife one with AB blood group and the other with A blood group will produce four genotypes and three phenotypes. It has been depicted by the cross given below Husband % IA IB IA IA IA IB IA i IB i & Wife IA i Thus, the genotypes and the phenotypes of the offspring would be Genotypes : 4(IA IA , IA IB , IA i, IB i) Phenotypes : 3 (A, B, AB) 53 (b) Dominance, codominance and multiple alleles are the characteristics that represent ‘inheritance of blood groups’ in humans. ABO blood groups are determined by the gene I. There are multiple (three) alleles; I A , I B and i of this gene. Allele I A and I B are dominant over i. However, when I A and I B alleles are present together, they show codominance. Therefore, option (b) is correct. 55 (a) Option (a) is correct. This can be explained as occasionally a single gene product may produce more than one effect. Like in starch synthesis in pea seeds controlled by one gene having two alleles (B and b). Thus, the phenotype and genotype expressed are l l l I AI B Blood group AB % & % A A Genotype BB–round seed, large starch synthesis. bb–wrinkled seed, less starch synthesis. Bb–round seed, intermediate starch synthesis. Thus, if we take size as a phenotype, allele B shows complete dominance over ‘b’, but if we take starch synthesis as a phenotype, allele B and b shows incomplete dominance. 57 (a) The formula to determine the number of gametes is 2n = 2(2) = 4 Thus, RrYy would produce 4 gametes of the types RY, Ry, rY, ry. www.mediit.in 59 (a) When plants bearing round yellow (RRYY) seeds are crossed with plants bearing and wrinkled green (rryy) seeds, all the plants in F1 -generation will have yellow round seeds. It can be depicted by the cross given below % & RY ry rryy RRYY x (Wrinkled, green) (Round, yellow) Parents Gametes 69 RrYy (Round, Yellow) F1-generation 60 (a) A cross between pure yellow round seeded plants 72 and pure green wrinkled seeded plants is shown below Parents (Wrinkled green) rryy RY ry Gametes × (Round yellow) RRYY 74 (Round yellow) RrYy F1-generation 78 Selfing RY RY Gametes Gametes rY Ry ry RRYy RrYy F2-generation RrYy RRyy rrYy Rryy ry RRYy rrYY 79 Ry RrYY RrYY RrYy rY RRYY RrYy rrYy 80 Rryy rryy Phenotypic ratio Round yellow : Round green : Wrinkled yellow : Wrinkled green 9 : 3 : 3 : 1 Genotypic 1 (RRYY) : 2 (RRYy) : 2 (RrYY) : 4 (RrYy) : 1 (RRyy) ratio 2 (Rryy) : 1 (rrYY) : 2 (rrYy) : 1(rryy) Thus, the number of plants of F2 -generation having yellow coloured seeds are 12 (out of 16). 64 (a) The genotypic ratio of a dihybrid cross is 1:2:2:4:1:2:1:2:1 Thus, we see that 9 different genotypes are observed in the F2 -generation. 65 (d) In 1900, three scientists (de Vries, Correns and von Tschermak) independently rediscovered Mendel’s results on the inheritance of characters. Also, by this time due to advancements in microscopy that were 85 taking place, scientists were able to carefully observe cell division. This led to the discovery of structures in the nucleus that appeared to double and divide just before each cell division. (d) Sutton and Boveri proposed the chromosomal theory of inheritance. In 1902, the chromosomal movement during meiosis was worked out. Walter Sutton and Theodore Boveri stated that pairing and separation of a pair of chromosomes would lead to the segregation of a pair of factors they carried. They united the knowledge of chromosomal segregation with Mendelian principles and called it chromosomal theory of inheritance. (b) Both genes and chromosomes (Mendelian factors) wheather dominant or recessive are transmitted from generation to generation in the pure or unaltered form. It is also called law of purity of gametes. (c) The pair given in option (c) is incorrect. It can be corrected as TH Morgan – Linkage de Vries – Mutation Rest of the pairs are correct. (b) When two genes in a dihybrid cross are situated on the same chromosome, the proportion of the parental gene combinations are much higher than the non-parental or recombinant type as linked genes are inherited together in offspring. (b) Alfred Sturtevant was the first to explain the concept of chromosomal mapping. It is constructed on the basis of recombination frequency between gene pairs on the same chromosome. This frequency is directly proportional to the distance between these two genes. It can be used to determine the exact location of a gene on the chromosome. (b) In the construction of genetic maps, map unit or centi Morgan is a unit or distance between genes on chromosomes, representing 1% cross over, i.e. 1 map unit = 1% cross over Hence, the genetic distance between genes is based on average number of cross over frequency between them. (a) Since, genes A and B are more close than genes A and C, therefore, gene A has to be present before genes B and C with gene B present in between genes A and C. Other options are incorrect and can be corrected as l l Gene C is not between genes A and B. More crosses have occurred between A and C than A and B. 88 (a) Human skin colour is another classic example for polygenic trait the phenotype reflects the contribution of each allele, i.e. the effect of each allele is additive. To understand this better let us assume that three genes, i.e. A, B and C control skin colour in human with the dominant forms A, B and C responsible for dark skin colour and the recessive forms a, b and c for light skin 117 Answers & Explanations CHAPTER 05 > Principles of Inheritance and Variation www.mediit.in 118 Master The NCERT > BIOLOGY (Vol-II ) 93 95 96 101 colour. The genotype with all the dominant alleles (AABBCC) will have the darkest skin colour and that with all the recessive alleles (aabbcc) will have the lightest skin colour. (c) In the given pairs, option (c) is wrongly matched. It can be corrected as Starch synthesis in pea is an example of pleiotropy. Rest of the pairs are correctly matched. (c) Option (c) contains the incorrect pair. It can be corrected as In Drosophila, XX-XY type of sex-determination is seen, i.e. same as humans. Rest of the pairs are correct. (a) In XX-XY type of sex-determination, male are heterogametic, i.e. produces two types of sperms with X and Y. But females are homogametic, i.e. produces only single type of ovum with X. (c) Sex-determination in honeybee is called haplo-diploid sex-determination system. Parents Gametes F1 - generation Female 32 Male 16 Meiosis Mitosis 16 16 Male 16 16 Female 32 102 (a) The sex-determination in honeybee is based on the 104 Answers & Explanations 105 107 108 number of sets of chromosomes an individual receives. An offspring formed from the union of a sperm and an egg develops as a female (queen or worker) and an unfertilised egg develops as a male (drone) by means of parthenogenesis. (a) Mutation is the phenomenon which results in alteration of DNA sequences and consequently results in change in the phenotype and genotype of an organism. The term ‘mutation’ was introduced by Hugo de Vries in 1901 in his mutation theory of evolution. (d) In most cases if there is a change in genotype than it ultimately leads to change in phenotype too. Mutation may also involve change in the rate of metabolism in some individuals. (b) Point mutations refer to those mutations which arise due to change in a single base pair of DNA. This change may either be deletion or addition of one or more bases or it may be due to substitution of one base by another. (d) Transition occurs when a purine base (A or G) is replaced by another purine base. Transversion occurs when a purine base is substituted by a pyrimidine base or vice-versa. Thus, the number of possible transitions and transversions among the four bases (A, T, G, C) are 4 and 8, respectivley and can be represented by the figure given below T 3 1 2 1 2 4 4 G A 3 8 6 7 5 C (Transition → and Transversion ) 110 (c) Deletion and insertion of one base leads to a change in the entire DNA base pair sequence, which leads to frame shift mutation. Since the deletion or insertion in DNA base pair sequence is occurring in the reading frame. This is named as frame shift mutation. 111 (c) Mutagens may be physical agents such as X-rays, α-rays, etc., which cause mutation and chemical agents such as mustard gas, etc., which cause changes in the DNA sequence in an organism. 112 (d) The study of inheritance of genetic traits in several generations of a family of human beings is done in the form of a family tree diagram called the pedigree chart and the method is called pedigree analysis. 116 (d) Cytoplasmic or Mitochondrial inheritance is the inheritance in which a trait is passed only from the mother to offspring. The genes involved in this mode of inheritance are present in the cytoplasm of ova. Since, after fertilisation, cytoplasm is contributed to the zygote by ova, the genes for a specific trait are passed on from the mother to the offspring. 117 (a) In the given pedigree chart only males are affected. So, it can be easily inferred that the given trait is connected to Y-chromosome. 118 (b) The type of pedigree given is autosomal recessive. It can be explained by the detailed pedigree chart given below Let ‘a’ be the recessive autosomal allele. Aa aa Aa aa aa Aa or Aa AA or Aa AA or Aa Aa AA or Aa aa Aa aa Aa AA or Aa Aa aa AA or Aa 119 (a) Figure (a) is correct as the case is that of criss-cross inheritance. It is a type of sex-linked inheritance, where a parent passes the traits to the grand child of the same sex through offspring of the opposite sex. The father passes the traits to grandson through his daughter (diagynic), while the mother transfers traits to her grand daughter through her son (dia-andric). www.mediit.in 119 CHAPTER 05 > Principles of Inheritance and Variation 120 (c) For the pedigree chart given in the question, the cause of the trait can either be due to a dominant allele or a recessive allele. It can be depicted by the two cases given below I. When ‘A’ is the dominant allele for the trait and ‘a’ is the normal recessive allele. aa Aa aa Parents XY × XcX (Normal man) (Carrier woman) AA aa Aa aa Aa Aa aa Aa aa aa II. When ‘a’ is the recessive allele for the trait and ‘A’ is the normal dominant allele. AA AA or Aa aa aa aa AA or Aa aa AA or Aa aa aa Aa Aa Aa 121 (d) The genotype of the individual marked ‘M’ has to be X h X, i.e. she has to be the carrier, so as to produce an individual who is affected, in the last generation. 122 (a) Inheritance of ear lobes is determined by an autosomal gene with two alleles. The allele ‘F’ for free ear lobe is dominant over allele ‘f ’ for attached ear lobe. Thus, the type of pedigree chart can only the obtained when the parents are heterozygous. It can be explained by the chart given below Ff Hence, out of the 4 offspring possible 25% of sons are diseased and 25% are normal. Similarly, 50% daughters normal out of which half are carriers. 125 (b) Colour blindness is an X-linked disease. So, a woman whose father is colourblind will be a carrier for the disease. Ff X Xc Y X Gametes XY F1-generation XX XXc XcY (Carrier (Normal (Colourblind (Normal son) daughter) daughter) son) So, the possibility of a colourblind daughter (i.e. X cX c) in F1 -generation is 0%. 126 (a) Colour blindness is a sex-linked recessive genetic disorder involving the X-chromosome. Thus, according to the situation given in the question, a man whose father was colourblind will be, normal, i.e. XY and a woman whose mother was colourblind and father was normal is a carrier, i.e. XX c. Thus, when marriage happens between two such individuals percentage of a male child to be colourblind is 25% (this can be easily observed from the cross given below) Carrier mother X XX Normal father Xc × X Y c Xc X XY X Y (Normal (Normal (Carrier (Colourblind daughter) son) daughter) son) Ff ff Ff Ff condition and she can transmit the carrier allele to both her son and daughter. The resulting son will affected because X-linked disorder always affect males as males contain a single X-chromosome. The daughter offspring will be a carrier, but not diseased because females are affected by X-linked disorder in homozygous recessive condition only, i.e. two recessive alleles are required. Parents Gametes XhX XY (Carrier mother) X (Normal father) Xh XhX F1 -generation Carrier X XhY X-linked daughter diseased son X XX 127 (a) A colourblind father (genotype X cY) would produce carrier daughters (genotype XX c). When a carrier female ( XX c ) marriages a normal man (XY), the types of offspring produced would be all normal daughters and half of the sons (50%) would be colourblind and the remaining half would be normal. This pattern of inheritance can be explained by the following cross (Carrier mother) XXc Gametes X × X XY X c X c XX X Y Normal Normal daughter son XY (Normal father) c X X X Y X Y c Y XY 128 (a) Haemophilia is an X-linked recessive gene disorder. It is a blood clotting disorder and shows criss-cross inheritance. In this, characters from father are transmitted to daughter and from mother to son. Answers & Explanations ff 124 (d) In the given problem, the woman has an X-linked www.mediit.in 120 Master The NCERT > BIOLOGY (Vol-II ) 129 (c) Haemophilia is a sex-linked recessive disease, which 132 133 136 137 138 Answers & Explanations 139 140 143 144 shows its transmission from unaffected carrier female to some of the male progeny has been widely studied. In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected. Due to this, in an affected individual, a simple cut will result in non-stop bleeding. (d) During phenylketonuria the affected individual lacks an enzyme that converts amino acid, phenylalanine into tyrosine (i.e. phenylalanine hydroxylase is absent). As a result of this phenylalanine is accumulated and converted into phenylpyruvic acid and other derivatives. This lack of the enzyme is due to the presence of autosomal defective gene on chromosome number 12. (d) Thalassemia is also an autosome linked recessive blood disease transmitted from parents to the offspring when both the partners are unaffected carrier for the gene (or heterozygous). The defect could be due to either mutation or deletion which ultimately results in reduced rate of synthesis of one of the globin chains (α and β-chains) that make up haemoglobin. This causes the formation of abnormal haemoglobin molecules resulting into anaemia which is characteristic of the disease. (a) Aneuploidy occurs when the chromatids fail to segregate during cell division, resulting in gain or loss of a chromosome. (a) Polyploid cells have a chromosome number that is more than double the haploid number, e.g. Triticum aestivum (wheat) is a hexaploid ( 6n ). (a) Non-disjunction in meiosis results in trisomy, i.e. the presence of an extra chromosome. Such individuals have 47 chromosomes instead of 46. Some examples of such abnormalities include Down’s syndrome (21-trisomy), Patau’s syndrome (13-trisomy) and Edward’s syndrome (18-trisomy). (a) Down’s syndrome is an abnormality caused by an autosomal primary non-disjunction. Non-disjunction is the failure of chromosomes to disjoin or separate and move away to opposite poles. Non-disjunction of 21st chromosome during oogenesis is the cause of Down’s syndrome. It occurs due to the presence of an additional copy of chromosome number 21 (trisomy of 21st chromosome) in humans. (c) Karyotype of people suffering from Down’s syndrome have 47 chromosomes ( 45 + XY in males, 45 + XX in females) instead of 46. It is caused due to the presence of an extra chromosome, i.e. chromosome number 21. Thus, it is also known as 21 trisomy. (a) In Klinefelter’s syndrome, the affected individual has overall masculine development, gynaecomastia and is sterile. This condition is represented by the karyotype 44 + X (47) due to the presence of an extra X-chromosome in males. (d) Both options (a) and (c) are correct. This can be explained as In klinefelter’s syndrome, the sex chromosomes genotype is XXY, i.e. there is one extra X-chromosome. 149 150 151 152 153 154 155 156 157 This extra X can come in two conditions, when there is non-disjunction in egg, i.e. XX egg and Y sperm and where is non-disjunction in sperm, i.e. X egg and XY sperm. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Offspring bear characteristics of both the parents. These characters pass from the parents via their gametes into their progeny. This is called inheritance. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. True breeding lines show inheritance of pure characters for several generations. This is because true breeding lines are homozygous for the traits. Therefore, Mendel conducted cross-pollination experiments, between different true breeding lines to study the concept of inheritance. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. There was no blending of characters in the progeny of F2 -generation. As a result, the offspring exhibited traits which were exactly identical to their parents. (d) Assertion is false, but Reason is true. Assertion can be corrected as Genes are passed on from one generation to the next, and thus called as the units of inheritance. (c) Assertion is true, but Reason is false and it can be corrected as Meiosis occurs during the process of gamete formation which leads to the formation of haploid gametes. (a) Both Assertion and Reason are true, but Reason is the correct explanation of Assertion. In codominance, the progeny of F1 -generation resembles both the parents due to the equal expression of the two alleles involved. An example of the phenomenon of codominance is ABO blood grouping in humans. In this antigen A, product of the alleles I A and antigen B, product of the alleles I B are codominant in individual with AB blood group. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. Behaviour of chromosomes is considered to be parallel to that of the genes. This is because, as genes are passed on from one generation to the next, chromosomes also get passed on from one generation to the next. (c) Assertion is true, but Reason is false and it can be corrected as Genes, which tend to get passed on together from one generation to the next, are located very close to each other on a chromosome. Such genes are called as linked genes. (d) Assertion is false, but Reason is true. Assertion can be corrected as Insects show male heterogamety as females have XX sex chromosomes and males have XO sex chromosomes. www.mediit.in CHAPTER 05 > Principles of Inheritance and Variation 159 160 161 162 163 164 165 166 corrected as Male honeybees, i.e. drones are haploid whereas female honeybees, i.e. queen and workers are diploid. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The non-allelic genes for red hair and prickles are inherited together as these are located in close association on the same chromosome. (c) Assertion is true, but Reason is false and it can be corrected as In Klinefelter’s syndrome males are sterile as individual possess 47 chromosomes (44 + XXY ). (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Phenylketonuria is an autosomal herditary disease, which occurs due to an autosomal defective gene on chromosome number 12. The defective gene causes body’s failure to oxidise amino acid, phenylalanine to tyrosine because of defective enzyme, phenylalanine hydroxylase. Thus, the patient shows the presence of phenylalanine acid in urine. (b) Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion. Sickle-cell anaemia is an autosomal linked recessive disorder. The gene for this disorder is present on an autosome and an individual is said to be affected only when both the genes or a pair of allele (mutated or affected) are inherited from the carrier or affected parents. (d) Assertion is false, but Reason is true. Assertion can be corrected as Down’s syndrome is a chromosomal disorder. It is caused due to the presence of an additional copy chromosome 21 (trisomy 21). (b) The statement in option (b) is not true. It can be corrected as The tightly linked genes on chromosomes show 100% parental types and 0% recombinants. Two genes that undergo independent assortment indicated by a recombinant frequency of 50% are on non-homologous chromosomes indicated for apart in a single chromosome. As the distance between two genes increases, crossing over frequency increases. This results in the formation of more recombinant gametes and fewer parental gametes. Rest of the statements are true. (c) The statement is option (c) is incorrect and can be corrected as The law of segregation applies universally. The reappearence of parental (red and white) flowers in the F 2 -generation also confirms, that law of segregation applies in this experiment. Rest of the statements are correct. (b) The statement in option (b) is incorrect and can be corrected as In domesticated fowls, sex of progeny depends on the type of egg rather than type of sperm. Rest of the statements are correct. 167 (b) The statement in option (b) correctly describes the manner of determining the sex. Rest of the statements are incorrect and can be corrected as l l l Heterozygous sex chromosomes (ZW) determine female sex in birds. XO condition in humans as found in Turner’s syndrome determines male sex. Heterozygous sex-chromosomes (XY) produces males in Drosophila. 168 (d) The statement in option (d) is incorrect and can be corrected as Female homogamety is found in mammals. Rest of the statements are correct. 170 (a) The statement in option (a) is incorrect and can be corrected as Humans contain 22 pairs of autosomes (XX) and one pair of sex chromosome (XY). Rest of the statements are correct. 171 (a) The statement in option (a) is incorrect for haemophilia and can be corrected as It is a sex-linked recessive disease. Rest of the statements are correct. 172 (c) The statement in option (c) is correct. Rest of the statements are incorrect and can be corrected as l l Sickle-cell anaemia is the qualitative defect of synthesising an incorrectly function globin. Thalassemia is the quantitative defect of synthesising to few globin molecules. 173 (c) The statement in option (c) is incorrect and can be corrected as In thalassemia, the α and β-globin chains of haemoglobin are not absent rather their production is affected. Rest of the statements are correct. 174 (d) The statement in option (d) is correct with respect to monohybrid cross and dihybrid cross. Rest of the statements are incorrect and can be corrected as l l l Both monohybrid and dihybrid crosses can be performed for one or more generations. Both monohybrid cross and dihybrid cross involves two parents. Both monohybrid cross and dihybrid cross can produce two or more progeny. 175 (a) The statement in option (a) is correct with respect to the law of segregation. Rest of the statements are incorrect and can be corrected as l The paired factors or alleles segregate from each other such that a gamete recieves only one of the factor present in the origin at paired form. Answers & Explanations 158 (c) Assertion is true, but Reason is false and it can be 121 www.mediit.in 122 Master The NCERT > BIOLOGY (Vol-II ) l Homozygous parent produces similar types of gametes whereas heterozygous ones produce two types of gametes each with one allele to equal proportion. 184 (d) Statements I, II and III all are incorrect and can be corrected as l 177 (b) The statement in option (b) is incorrect and can be corrected as The vast majority of mutations produce recessive alleles. 178 (c) Statements I and IV are correct. Statements II and III are incorrect and can be corrected as l l Characters blend in both homozygous and heterozygous conditions. Not all characters (only some) show dominance in humans. l l 185 (a) Statements I and II are the correct reasons for why Mendel could not find out about linkage. Statements III and IV are incorrect and can be corrected as l 179 (a) Statement I is the only correct statement about linkage. Rest of the statements are incorrect and can be corrected as l l l Less parental combinations are produced in F2-generation. Genotype which were present in F1 hybrid, reappeared in low frequency in F2-generation. Linkage is the phenomenon in which two genes are physically linked. 180 (b) Statement I is correct. Statements II, III and IV are incorrect and can be corrected as l l l A recessive allele is not weaker than the dominant allele. A recessive allele does not show its effect because of modified or different enzymes. A recessive allele can express in few cases, e.g. incomplete dominance. It is not necessary that dominant allele is always better. Lightly linked genes on the same chromosome show low recombination. Genes far apart on the same chromosome show high or more recombination. Genes loosely linked on the same chromosome show higher recombination than tightly linked genes. The genes for all the traits were present on different chromosomes or were located for apart on the same chromosomes. 190 (d) Both statements I and II are false and can be corrected as In male and female insects, the number of chromosomes are not same. The females are homozygous, containing XX chromosomes, while males contain only one X-chromosome and represented as XO. 207 (b) All the genes, present on a particular chromosome form a linkage group. The number of linkage group of a species corresponds to the total number of different chromosomes of that species. 208 (b) If a cross between two tall plants resulted in a few dwarf offspring, then the parental genotypes are Tt and Tt. It can be explained by the following example The F1 plants of genotype, Tt are self-pollinated [both tall (T), but with dwarf (t) alleles]. 181 (b) Statement I is incorrect and can be corrected as Mutations are not acquired as they occur by chance and are selected by nature. Rest of the statements are correct. 182 (b) Statements I and II are correct. Statements III and IV are incorrect and can be corrected as Answers & Explanations l l Codominance cannot be manifested phenotypically in humans as ABO blood group in humans is three alleles of gene I (IA ,IB ,i). ABO blood grouping system in humans does not follow Mendel’s laws of inheritance. 183 (d) Statements I and II are correct. Statements III and IV are incorrect and can be corrected as l l Dihybrid test cross ratio is 1 : 1 : 1 : 1 in F2-generation, i.e. show 4 phenotypes and genotypes in equal proportions. Linked genes do not separate frequently.These genes remain together because linked gene lie very closely to each other. t T TT × Tt t T Tt Selfing tt F1-generation Phenotypic ratio : Tall : Dwarf 3 : 1 Genotypic ratio : Pure tall : Hybrid : Pure dwarf : 2 : 1 1 209 (d) If a 9 : 3 : 3 : 1 ratio is obtained in a dihybrid cross, it denotes that alleles of two genes are segregate independently. It can be explained as follows If a pea plant with round and yellow seeds is crossed with a plant with wrinkled and green ones all F1 hybrids possess yellow and round seeds. Since, yellow colour is dominant over the green and the round shape is dominant over the wrinkled. www.mediit.in 123 CHAPTER 05 > Principles of Inheritance and Variation When IA and IB are present together, both express equally and produce the surface antigens A and B. Thus, a person having genotype IA IB would show the blood group as AB. 216 (c) When both mother and father are heterozygous for ‘A’ and ‘B’ blood group, respectively. Then few of their progeny would be with ‘O’ blood group. This can be explained as 210 (d) Mendel’s dihybrid cross is depicted below (Wrinkled green) Parental rryy generation Gametes ry RY (Round-yellow) RrYy F1 -generation Selfing Parents Phenotypic Round : Round : Wrinkled : yellow green yellow ratio 9 : 3 : 3 : Genotypic 1:2 : 2 : 4 : 1 : 2 : 1 ratio Wrinkled green 1 : 2 : Gametes 211 (d) The ratio of offspring will be 1 : 1 for the cross mentioned in the question. This can be explained as × aabb (Homozygous recessive) AB ab ab Only these two gametes will be formed because 'A' and 'B' are linked genes ab AB AaBb 1 ab aabb 1 Thus, both genotypic and phenotypic ratio will be 1 : 1. 215 (b) ABO blood grouping in humans is an example of codominance. IB Mother (A group) I Ai IA i i 1 Thus, from the cross, it can be determined that the number of phenotypes and genotypes in the F2 -generation of a Mendelian dihybrid cross is 4 and 9, respectively. AaBb (Heterozygous) Father (B group) I Bi F1 -generation I AI B AB blood group I Bi B blood group I Ai A blood group ii O blood group 217 (a) The distance between the genes and percentage of recombination shows a direct relationship. This can be explained as when genes are close together, or are linked exhibit low recombination frequencies. And when they are far apart the recombination is high. 219 (a) The 17 and 18 chromosomes bearing organisms are males and females, respectively. In large number of insects like cockroach and grasshopper, XX-XO type of sex-determination is seen, which shows male heterogamety. Here XX represent females and XO (which is basically single X chromosome) represents males. Therefore consequently the number of chromosomes in them would be 17 in males and 18 in females. 223 (a) Aneuploidy involves changes in the chromosome number either by additions or deletions of less than a whole set. In this case organism gains or loses one or more chromosomes but not a complete set. Thus, the karyotypic conditions of 2n ± 1 or 2n ± 2 denote aneuploidy. Answers & Explanations (Round yellow) RRYY www.mediit.in CHAPTER > 06 Molecular Basis of Inheritance NEET Å Å KEY NOTES Mendel suggested that there are some factors or genes which help to maintain the phenotypes and genotypes of organisms for generation after generation. It was later established that DNA (Deoxyribonucleic Acid) is the genetic material in majority of organisms, while RNA acts as the genetic material in some viruses, but has additional roles as well. RNA functions as adapter, structural and in some cases as catalytic molecule. DNA (Deoxyribonucleic Acid) Å Å It is a long polymer of deoxyribonucleotides. The length of DNA is usually defined as number of nucleotides (or a pair of nucleotide referred to as base pairs) present in it. For example, a bacteriophage known as φ × 174 has 5386 nucleotides, bacteriophage lambda has 48502 bp, Escherichia coli has 4.6 × 206 bp and haploid content of human DNA is 3. 3 × 109 bp. Structure of a Polynucleotide Chain A nucleotide is composed of a nitrogenous base, pentose sugar and a phosphate group. 1. A nitrogenous base It is the nitrogen containing organic molecule having similar physical properties of a base. Å There are two types of nitrogenous bases Purines Adenine and Guanine. Pyrimidines Cytosine, Uracil and Thymine. Å Thymine is present in DNA, while uracil is present in RNA in place of thymine (5-methyl uracil, another name for thymine). n n 2. A pentose sugar Two types of sugars are present Å Discoveries Related to Structure of DNA Å Friedrich Miescher in 1869, first identified DNA as an acidic substance present in the nucleus and named it as ‘nuclein’. Å James Watson and Francis Crick, proposed a very simple double helix model for the structure of DNA in 1953 based on X-ray diffraction data. Å Erwin Chargaff proposed that for a double-stranded DNA, the ratio between adenine and thymine and guanine and cytosine are constant and equals one. A+G A + G = T + C or =1 T+C Ribose (in case of RNA) Deoxyribose (in case of DNA) 3. A phosphate group It is in the form of H3 PO4 . Å Å Nucleoside and nucleotide A nucleoside is formed when a nitrogenous base is linked to a pentose sugar through N-glycosidic linkage. Å Nucleotides are the phosphoric esters of nucleosides. n n Nucleotides are joined by 3′−5′ phosphodiester bonds to form a dinucleotide. Alternate deoxyribose and phosphate residues joins to form the polynucleotide chain. Double Helix Structure of DNA Å Å DNA is made up of two polynucleotide chains, where the backbone is constituted by sugar, phosphate and the bases project inside. The two chains have anti-parallel polarity, i.e. 5′→ 3′ for one, 3′→ 5′ for another. www.mediit.in 125 CHAPTER 06 > Molecular Basis of Inheritance Å Å Å The bases in two strands are paired through hydrogen bond (H—bonds) forming base pairs (bp). Adenine forms two hydrogen bonds with thymine and vice-versa. Guanine bonds with cytosine by three H—bonds and vice-versa. Thus, a purine always comes opposite to a pyrimidine forming a uniform distance between the two strands. The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm and there are roughly 10 bp in each turn. Due to this, the distance between a base pair in a helix is about 0.34 nm. The plane of one base pair stacks over the other in double helix. This confers stability to the helical structure in addition to H—bonds. The Search for Genetic Material The experiments given below established that DNA is the genetic material in majority of organisms. Transforming Principle Å Å Central Dogma Å Injection S-strain → Mice → Mice died In 1957, Francis Crick proposed the central dogma in molecular biology. According to this, the genetic information flows from DNA → RNA → Protein. DNA replication DNA Transcription Translation mRNA Injection R-strain → Mice → S-strain → Mice → Mice live (Heat-killed) Injection Protein S-strain → Mice → Mice die (Heat-killed) + R-strain (Live) The flow of information can be in reverse direction also, i.e. from RNA to DNA in some viruses, such as TMV. Å Packaging of DNA Helix Å Å Å Å Å Å Mice lived Injection Central dogma Å Frederick Griffith (1928) carried out a series of experiments with Streptococcus pneumoniae (bacterium causing pneumonia). He used two strains of this bacterium, i.e. one forming smooth colonies with capsule (S-type) and the other forming rough colonies without capsule (R-type) and gave the following observations In prokaryotes, such as E. coli, the DNA is not scattered throughout the cell even though they do not have a defined nucleus. DNA (being negatively charged) is held with some proteins (that are positively charged) in a region termed as nucleoid. The DNA in nucleoid is organised in large loops held by proteins. In eukaryotic cells, there is a set of positively charged proteins called histones. Histones are rich in basic amino acid residuces lysine and arginine. These are organised to form a unit of eight molecules called histone octamer. The negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called nucleosome. A typical nucleosome contains 200 bp of DNA helix. Nucleosome constitutes the repeating unit of a structure in the nucleus called chromatin, thread-like stained (coloured) bodies seen in nucleus. The ‘beads-on-string’ structure of nucleosome in chromatin are packaged to form chromatin fibres which further coil and condense at metaphase stage of cell division to form the chromosomes. The packaging of chromatin at higher level requires additional set of proteins that collectively are referred to as Non-Histone Chromosomal (NHC) proteins. Some regions of chromatin which are loosely packed (stain light) are called euchromatin (active chromatin). In some regions, chromatin is densely packed (stain dark), it is called heterochromatin (inactive chromatin). He concluded that the R-strain bacteria had somehow been transformed by the heat-killed S-strain bacteria, which must be due to the transfer of the genetic material (transforming principle). Biochemical Characterisation of Transforming Principle Å Å Å Å Å Oswald Avery, Colin MacLeod and Maclyn McCarty (1933-44) worked to determine the biochemical nature of ‘transforming principle’ in Griffith’s experiment in an in vitro system. From the heat-killed S-cells, they purified biochemicals (proteins, DNA, RNA, etc.) to observe, which biochemical could transform live R-cells into S-cells. They discovered that DNA alone from heat-killed S-type bacteria caused the transformation of non-virulent R-type bacteria into virulent S-type bacteria. Protein-digesting enzymes (proteases) and RNA digesting enzymes (RNases) did not cause this transformation. This proved that the ‘transforming substance’ was neither protein nor RNA. DNA-digesting enzyme (DNase) caused inhibition of transformation, which suggested that DNA caused the transformation. Thus, it was concluded that DNA is the hereditary material. The Genetic Material is DNA Å Å Alfred Hershey and Martha Chase gave another definitive evidence for DNA as genetic material in 1952. In their work, they described that the phage DNA enters the host cell and works as a genetic material. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 126 Å Outline of their experiment is given below [Viral DNA labelled] 32 DNA labelled with P [Viral coat labelled] Protein coat labelled with 35S Viruses have infected bacteria Viruses have infected bacteria Blender separates viral coats from bacteria Blender separates viral coats from bacteria Viral replication occurs Viral replication occurs Å Therefore, DNA has evolved from RNA with chemical modifications which make it more stable. Å There are following three types of RNA, i.e. messenger RNA ( mRNA), which provides the template for transcription, transfer RNA (tRNA) which brings amino acids and reads the genetic code and ribosomal RNA ( rRNA), which plays structural and catalytic role during translation. DNA Replication Å Radioactivity within bacterial DNA Radioactivity within viral coats Radioactive DNA enters Radioactive protein did not enter from phage to bacteria indicating from virus to bacteria indicating that that DNA acts as genetic material protein does not act as genetic material (a) (b) The Hershey and Chase experiment Properties of Genetic Material (DNA v/s RNA) Å Å Genetic material is the substance which controls the inheritance of traits from one generation to next. Following are the criteria that a molecule must fulfil to act as a genetic material It should be able to replicate itself. It should be stable both chemically and structurally. It should provide the scope for slow changes (mutation), which are required for evolution. It should be able to express itself in the form of ‘Mendelian characters’. Scheme for replication of DNA termed as semiconservative DNA replication was proposed by Watson and Crick (1953). According to this, the two strands would separate and act as a template for the synthesis of new complementary strands. Thus, each DNA molecule formed would have one parental and one newly synthesised strand. The Experimental Proof Matthew Meselson and Franklin Stahl (in 1958) conducted the following experiment with Escherichia coli to prove that DNA replicates semiconservatively. Å They grew many generations of E. coli in a medium that contained 15 NH4Cl ( 15 N is the heavy isotope of nitrogen) as the only source of nitrogen. n n Å n n Å DNA from such bacterium had an intermediate density (hybrid), one generation after the transfer from 15 N to 14 N. After another generation, it was composed of equal amount of hybrid DNA and light DNA. Å Similar experiments on ‘Vicia faba’ (faba beans) were conducted by Taylor and colleagues in 1958, involving the use of radioactive thymidine. The results were that the DNA in chromosomes also replicate semiconservatively. Differences between DNA and RNA DNA RNA It is double-stranded with exception of some viruses. It is generally single-stranded. It is the genetic material in all living organisms. It is the genetic material in some viruses only. The sugar is deoxyribose. The sugar is ribose. Nitrogenous bases present are adenine, Nitrogenous bases present are guanine, thymine and cytosine. adenine, guanine, cytosine and uracil. It is chemically less reactive and structurally more stable. It is chemically more reactive and structurally less stable. It usually occurs inside the nucleus and in some cell organelles. Small amount of RNA occurs inside the nucleus. Most of it is found in the cytoplasm. The Machinery and the Enzymes The process of replication requires a set of catalysts (enzymes) which are given below Å DNA-dependent DNA polymerase It is the main enzyme which uses a DNA template to catalyse the polymerisation of deoxynucleotides. These enzymes are highly efficient and also help in removing mismatched nucleotides by a mechanism called proof reading. Å Helicase This enzyme unwinds the DNA strand, i.e. separates the two strands from one point, for the formation of a replication fork. RNA World Å Å Ribonucleic Acid (RNA) is said to be the first genetic material. It is evident through various scientific researches that essential life processes such as metabolism, translation and splicing, etc., evolved around, RNA. RNA used to act as genetic material as well as a catalyst. But RNA being a catalyst was reactive and hence unstable. NEET They observed that 15 N was incorporated into the newly synthesised strand of DNA. This heavy DNA could be distinguished from the normal DNA by centrifugation in a cesium chloride (CsCl) density gradient. KEY NOTES www.mediit.in 127 CHAPTER 06 > Molecular Basis of Inheritance Å Å Topoisomerase The unwinding of DNA creates a tension in the DNA strands, which gets released by the enzyme topoisomerase. DNA ligase It facilitates the joining of DNA strands together by catalysing the formation of phosphodiester bond. It also repairs single strand breaks in duplex DNA. Process of DNA Replication Å Å Å Å Å Replication is an energy expensive process, deoxyribonucleoside Triphosphates (dNTPs) serve the dual purpose of acting as a substrate and providing energy (from two terminal phosphates). Transcription Unit and The Gene Å Gene is the functional unit of inheritance. The DNA sequence coding for tRNA or rRNA molecule also defines a gene. Å Cistron is the segment of DNA which codes for a polypeptide. Å In a transcription unit, the structural gene could be Å In a long DNA molecule, replication takes place within a small opening of the DNA helix, known as replication fork. Replication begins at a definite region in a E. coli, DNA molecule known as origin of replication (ori), which has recognition site for DNA polymerase and also provides site for attachment of RNA primer. Monocistronic (mostly in eukaryotes). Polycistronic (mostly in bacteria or prokaryotes). The monocistronic structural genes in eukaryotes have interrupted coding sequences. They are of two types n DNA-dependent DNA polymerases catalyse polymerisation only in one direction, i.e. 5′→3′. Due to this, on one strand called the leading strand with polarity 3′→5′, replication is continuous. While on the other strand called the lagging strand with polarity 5′ → 3′ replication is discontinuous, i.e. in small fragments called Okazaki fragments. The fragments synthesised are joined by DNA ligase. n n n Å Exons are the coding sequences or expressed sequences that appear in mature or processed RNA. Introns are the intervening sequences which do not appear in mature or processed RNA. These only interrupt exons. The split gene, i.e. gene with both exons and introns is a characteristic of eukaryotic DNA. The promoter and regulatory sequences of a structural gene also affect the inheritance of a character. Hence, the regulatory sequences are sometimes loosely defined as regulatory genes. Transcription in Prokaryotes Å Transcription It is the process of copying genetic information from one strand of the DNA into RNA. This process is governed by the principle of complementarity, except adenosine now forms base pair with uracil instead of thymine. DNA-dependent RNA polymerase is the single enzyme that catalyses transcription of all types of bacterial RNA, and takes place in the following three steps Initiation RNA polymerase binds to promoter and initiates transcription by associating transiently with initiation factor (σ). Elongation Chain elongation proceeds in the 5′→ 3′ direction and the transcription bubble travels with RNA polymerase. The RNA polymerase after initiation of transcription loses the σ factor, but continues the polymerisation of ribonucleotides to form RNA. Termination When RNA polymerase reaches the terminator region of DNA, which is GC rich and has a hairpin-like structure, the nascent RNA separates and the RNA polymerase falls off resulting in termination of transcription. n n Transcription Unit Å A transcription unit of DNA is defined primarily by three regions in the DNA A promoter The structural gene A terminator n n n n Å Å The enzyme DNA-dependent RNA polymerase catalyses the polymerisation in only one direction (i.e. 5′→ 3′ direction). The strand with 3′ → 5′ polarity is known as the template strand. The strand with 5′ → 3′ polarity and same sequence as RNA (except thymine at the place of uracil) displaced during transcription, is known as coding strand. Å A promoter is a DNA sequence that provides binding site for RNA polymerase. It is located at 5′ end (upstream) of the structural gene and its presence defines the template and coding strands. Å The structural gene in a transcription unit is flanked by the promoter and terminator. Å A terminator is located towards the 3′ end (downstream) of the coding strand. It usually defines the end of transcription. Transcription in Eukaryotes The process of transcription in eukaryotes is similar to that in prokaryotes. Structural genes are monocistronic in eukaryotes. Two additional complexities are present in eukaryotes as given below Å The first complexity is that there are atleast three RNA polymerases in nucleus in addition to RNA polymerase found in organelles and these are n RNA polymerase-I transcribes rRNAs (28S, 18S, 5.8S). NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 128 RNA polymerase-II transcribes precursor of mRNA, which is called heterogeneous nuclear RNA (hnRNA). RNA polymerase-III transcribes tRNA, 5srRNA (small ribosomal RNA) and snRNAs (small nuclear RNAs). The second complexity is that the primary transcript contains both exons and introns. Thus, the process of splicing is performed to remove the introns and join the exons in a proper order to allow translation. The RNA formed is called hnRNA, which undergoes additional processing as follows Capping In capping, methyl guanosine triphosphate, an unusual nucleotide is added to the 5′ end of hnRNA. Tailing In tailing, adenylate residues are added at 3′ end in a template independent manner. n Å n Å Å The tRNA has a secondary structure like clover leaf. But its three dimensional structure depicts it as an inverted L-shaped molecule. tRNA has five arms or loops, as follows n n n n n Anticodon loop has bases complementary to the code. tRNAs are specific for specific amino acid. Amino acid acceptor end where amino acids bind. T-loop helps in binding to ribosome. D-loop helps in binding aminoacyl synthetase. Variable loop is variable in both nucleotide composition and in length. n Translation n Å The fully processed hnRNA, now called mRNA, gets transported out of the nucleus for translation. Genetic Code Å Å It is the relationship between the sequence of nucleotides on mRNA and the sequence of amino acids in the polypeptide. Important features of genetic code include The codon is triplet. 61 codons code for all amino acids and 3 codons do not code for any amino acids, hence, they function as stop codons. Some amino acids are coded by more than one codon hence, the code is degenerate. Genetic code is unambiguous and specific, i.e. one codon codes for only one amino acid and is read in a contiguous fashion without any punctuation marks. The genetic code is nearly universal, i.e. one codon codes for the same amino acid in all organisms. AUG codon has dual function, i.e. it codes for the amino acid methionine (met) and also acts as an initiation codon. Three codons function as stop codon or non-sense codons, which are UAA (ochre), UGA (amber), UAG (opal). n The process by which the triplet base sequence (codon) on mRNA guides the linking of a specific sequence of amino acids to form a polypeptide on ribosomes is known as translation. Translation Machinery Translation requires a machinery which consists of ribosome, mRNA, tRNAs, aminoacyl tRNA synthetase (enzyme that helps in combining amino acid to particular tRNA) and amino acids. Å Initiator tRNA It is a specific tRNA for the process of initiation and there are no tRNAs for stop codons. Å Ribosome It is responsible for protein synthesis. Ribosome exists as two subunits in its inactive stage n n n n n n n tRNA : The Adapter Molecule Å The presence of an adapter molecule, which could read the code and would bind to specific amino acids during translation was proposed by Francis Crick in 1961. Å tRNA was known before genetic code and was called sRNA (soluble RNA), but later its role as an adapter molecule was reported. NEET Large subunit It consists of two sites, where amino acids can bind to and be close to each other for the formation of a peptide bond. Ribosome also acts as a catalyst (23S rRNA in bacteria is the enzyme, ribozyme) for peptide bond formation. Å Translational unit It is the sequence of RNA flanked by the start codon (AUG) and the stop codon in mRNA. It codes for the polypeptide to be produced. Å Untranslated Regions (UTRs) These are some additional sequences in an mRNA which are not translated. These are present at both the ends, i.e. at 5′ end (before start codon) and at 3′ end (after stop codon). These improve the efficiency of translation process. Mutations and Genetic Code The sudden inheritable change in the genetic material is defined as mutation. These include Å Point mutation is mutation in a single base pair, which is replaced by another base pair, e.g. in sickle-cell anaemia, a point mutation in β-globin chain results in the change of amino acid residue glutamate to valine. Å Frameshift mutation is a change in the reading frame because of insertion or deletion of base pairs. Small subunit When the small subunit encounters an mRNA, translation of mRNA to protein begins. Stages of Protein Synthesis Synthesis of proteins takes place in three stages which are as follows 1. Initiation In prokaryotes, initiation requires ribosome (large and small subunits), mRNA, initiation tRNA and three Initiation Factors (IFs). For initiation to take place, the ribosome first binds to mRNA at the start codon (AUG) that is recognised only by the initiator tRNA. KEY NOTES www.mediit.in 129 CHAPTER 06 > Molecular Basis of Inheritance Å Å Activation of amino acid The formation of peptide bond requires energy and in first phase, the amino acids are activated in the presence of ATP and linked to their cognate tRNA by a process known as charging of tRNA or aminoacylation of tRNA. In the presence of ATP and Mg 2+ , amino acids become activated by binding with aminoacyl tRNA synthetase enzyme. Å Å Francois Jacob and Jacque Monod in 1961 were the first to propose the concept of a transcriptionally regulated system, where a polycistronic structural gene is regulated by a common promoter and regulatory genes. Å Such an arrangement is referred as an operon, e.g. lac (lactose) operon, trp (tryptophan) operon, ara (arabinose) operon, his (histidine) operon and val (valine) operon, etc. Å Let us take the example of lac operon. Its structure consists of various genes as follows Å One regulatory gene (the i gene), which codes for the repressor of the lac operon. The term i refers to the word inhibitor. Å Three structural genes are z gene codes for β-galactosidase (β-gal), that helps in the hydrolysis of disaccharide into its monomeric units, i.e. lactose into galactose and glucose. The amino acids − AMP− enzyme complex is called an activated amino acid. 2. Elongation of polypeptide chain In this step, another charged aminoacyl tRNA complex binds to the A-site of the ribosome. Å Lac Operon A peptide bond forms between carboxyl group (COOH) of amino acid at P-site and amino group ( NH3 ) of amino acid at A-site in a reaction catalysed by the enzyme peptidyl transferase. n During this stage, ribosome moves from one codon to another codon along the mRNA in the 5′ → 3′ direction. Amino acids are then added one-by-one in the sequence of codons and translated into a polypeptide sequences, dictated by DNA and represented by mRNA. 3. Termination of polypeptide When the A-site of ribosome reaches a termination codon, then no tRNA binds to the A-site of ribosome. At the end, a release factor binds to the stop codon and which terminates translation and releases the complete polypeptide from the ribosome. n n Å Gene expression results in the formation of a polypeptide. Gene regulation is the mechanism of switching ‘off ’ and switching ‘on’ of the genes depending upon the requirement of the cells and the stage of development. The regulation of gene expression may occur at various levels. In eukaryotes, it takes place at the following levels Transcriptional level A primary transcript is formed. Processing level Regulation of splicing. Transport of mRNA From nucleus to the cytoplasm. Translational level An inducer, i.e. lactose here which is the substrate for the enzyme β-galactosidase. Å If lactose is provided as the carbon source in the growth medium then in the absence of the preferred carbon source such as glucose, the lactose is transported into the cells by the action of enzyme permease. The lactose then induces the operon. Å The i gene synthesises the repressor of the operon. Repressor binds to the operator region of the operon, preventing RNA polymerase from transcribing the operon. However, when inducer such as lactose or allolactose is present, it binds with the repressor and inactivates it. Now, that the repressor is inactivated, RNA polymerase is allowed access to the promoter and transcription proceeds. Å Regulation of lac operon by repressor is referred to as negative regulation. Lac operon can work under the control of positive regulation also. n n n n Å In prokaryotes, control of the transcriptional rate of initiation is the predominant site for control of gene expression. In a transcription unit, the activity of RNA polymerase at a given promoter is in turn regulated by the interaction with accessory proteins, which affect its ability to recognise start sites. Å The accessibility of promoter regions of prokaryotic DNA in many cases is regulated by the interaction of operators. Å The operator region is adjacent to the promoter elements in most operons and in most cases operator bind a repressor protein. Each operon has its specific operator and specific repressor, e.g. lac operator is present only in the lac operon and it interacts with lac repressor only. a gene codes for a transacetylase. Å Regulation of Gene Expression Å y gene codes for permease, that increases the permeability of the cell to β-galactosides. Human Genome Project (HGP) Å In 1990, a mega project was started to determine the nucleotide sequence of the entire human nuclear genome. It was called as Human Genome Project (HGP). Å In addition, HGP was also entrusted to elucidate the genomes of several other model organisms, e.g. E. coli, Saccharomyces cerevisiae (yeast), roundworm and mouse. It was closely associated with the rapid development of a new area in biology called bioinformatics. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 130 Goals of HGP Important goals of HGP were Å To identify all the approximately 20,000-25,000 genes in human DNA. Å To determine the sequences of the 3 billion chemical base pairs that constitute human DNA. Å Å Å Å To store this information in databases in digital format. To improve the tools required for data analysis. To transfer the related technologies to other sectors (like industries). To address the Ethical, Legal and Social Issues (ELSI) that could arise from the project. Methodologies of HGP Two major approaches involved were as follows Å Repeated sequences are stretches of DNA sequences, which are repeated many times (some times 100-1000 times). These have no direct coding functions, but help in understanding chromosome structure, dynamics and evolution. Å Chromosome-1 has the maximum number of genes (2968) and Chromosome-Y has the least number of genes (231). Å There are about 1.4 million locations in human genome, where single-base DNA differences occur (SNPs− Single Nucleotide Polymorphisms). This information is helpful in finding chromosomal locations for disease-associated sequences and tracing human history. Applications and Future Challenges Å Expressed Sequence Tags (ESTs) This method was focused on identifying all the genes that are expressed as RNA. Å Its knowledge is helpful in research involving biological systems including human biology. Å Sequence annotation This method involved sequencing the whole set of genome (that contained all coding and non-coding sequence) and then assigning functions to the different regions in the sequence. Å All the genes in a genome, e.g. all the transcripts in a particular tissue/organ/tumour, can be studied. Sequencing of Genome Å Å Å Å Å For the process of sequencing, the entire DNA from a cell is isolated and broken into relatively smaller fragment. DNA fragments are cloned in a suitable host, (such as bacteria and yeast) using specialised vectors such as BAC (Bacterial Artificial Chromosome) and YAC (Yeast Artificial Chromosome). Fragments of DNA are then sequenced by automated DNA sequencers, which work on the principle of a method developed by Frederick Sanger. These sequences were arranged accordingly on the basis of overlapping regions of DNA fragments and were then aligned using special computer programmes. DNA Fingerprinting Å It also called DNA typing or DNA profiling and is a technique of determining nucleotide sequences of certain areas of DNA which are unique to each individual. Å It uses satellite DNA as probe showing high degree of polymorphism and called it Variable Number of Tandem Repeats (VNTRs). It was discovered by Alec Jeffreys in 1985. Å The technique has the following steps DNA isolation DNA is extracted from the cells in a high speed centrifuge. Amplification Many copies of the extracted DNA can be made by the use of Polymerase Chain Reaction (PCR). Digestion of DNA by restriction endonucleases. Separation of DNA fragments by electrophoresis. Blotting-transfer of the separated DNA fragments to synthetic membranes like nylon or nitrocellulose (Southern blotting). Hybridisation with the help of a radiolabelled VNTR probe. These proteins target a specific nucleotide sequence that is complementary to them. n n At last, the genetic and physical maps of the genome were constructed by collecting information about certain repetitive DNA sequences and DNA polymorphism. n n n Salient Features/Observations of Human Genome Å Å Å Å Å There are 3164.7 million nucleotide bases in the human genome. In an average gene, there are 3000 bases. The largest known human gene is Dystrophin (2.4 million bases). Total number of genes in human genome are estimated at 30, 000. Almost, all (99.9%) of the nucleotide bases are exactly same in every human individual. For over 50% of the discovered genes, the functions are unknown. Less than 2% of the genome codes for proteins. NEET n n Autoradiography Detection of hybridised DNA fragments by autoradiography. Applications of DNA Fingerprinting Å Å Å It helps to settle paternity or maternity disputes. It is used to identify perpetrators of sexual assault cases. It is used identify racial groups. KEY NOTES www.mediit.in CHAPTER 06 > Molecular Basis of Inheritance 131 Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ The DNA 10 Which of the following are all nucleotides? 1 DNA is a (a) (b) (c) (d) long polymer of deoxyribonucleotides short polymer of deoxyribonucleotides monomer polymer of deoxyribonucleotides long polymer of ribonucleotides 11 A polymer or a polynucleotide chain has at one end a 2 The length of DNA usually depends on (a) (b) (c) (d) free ........A....... at 5′ end of sugar, similarly at the other end of the polymer the sugar has a free .....B..... of 3′ group. position of nucleotides number of nucleotides Both (a) and (b) None of the above 3 Find the incorrect match. (a) A bacteriophage (φ × 174) –5386 nucleotides (b) Bacteriophage lamda – 48502 base pairs (c) E. coli – 4.6 × 106 bp (d) Haploid content of human DNA – 3.3 × 10 bp 6 4 Purines found both in DNA and RNA are NEET 2019 (a) adenine and guanine (c) cytosine and thymine (b) guanine and cytosine (d) adenine and thymine 5 Nitrogenous bases are linked to sugar by (a) hydrogen bond (c) N-glycosidic bond (b) phosphodiester bond (d) O-glycosidic bond 6 Nucleoside is formed when the nitrogenous bases are linked to (a) sugar (c) proteins (b) phosphate (d) fats 7 What is the difference between adenosine and deoxyadenosine? (a) Only sugar (c) Only phosphate (a) Adenosine, cytidilic acid, cytosine AIIMS 2019 (b) Adenylic acid, cytidilic acid, guanylic acid (c) Cytidine, adenine, adenylic acid (d) Uracil, thymidine, thymidylic acid (b) Only purine (d) All of these 8 When a phosphate group is linked to ...A... group of nucleoside through ...B... bond, a corresponding ...C... is formed. Choose the correct option for A, B and C. (a) A–5′ OH, B–phosphodiester bond, C–nucleotide (b) A–3′ OH, B–phosphodiester bond, C–nucleotide (c) A–2′ OH, B–phosphodiester bond, C–nucleotide (d) A–5′ OH, B–phosphodiester bond, C–nucleoside 9 Choose the correct option. (a) Pyrimidines include adenine and guanine (b) Pyrimidines include cytosine, uracil and thymine (c) Purines include adenine and thymine (d) Purines include guanine and cytosine (a) A – Phosphate moiety, B – OH (b) A – OH, B – Phosphate moiety (c) A – COOH, B – Phosphate moiety (d) A – Phosphate moiety, B–COOH 12 Backbone of DNA is formed by (a) (b) (c) (d) sugar phosphates Both (a) and (b) nitrogenous bases (purine and pyrimidine) 13 Thymine is also called (a) 2 methyl uracil (c) 4 methyl uracil (b) 3 methyl uracil (d) 5 methyl uracil 14 Choose the incorrect option. (a) Friedrich Miescher in 1869 identified DNA as an acidic substance and named it nuclein (b) Erwin Chargaff said, the ratio between A and T and G and C of dsDNA are constant and equals one (c) The two strands of dsDNA are complementary to each other (d) None of the above 15 X-ray data diffraction of DNA was produced by (a) Watson and Crick (c) Bateson and Punnett (b) Wilkins and Franklin (d) Both (a) and (b) 16 In DNA 20% bases are adenine. What percentage of bases are pyrimidines? (a) 30% (b) 60% JIPMER 2019 (c) 50% (d) 20% 17 In sea urchin DNA, which is double-stranded 17% of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this CBSE-AIPMT 2015 DNA are (a) (b) (c) (d) G/34%, A/24.5%, T/24.5% G/17%, A/16.5%, T/32.5% G/17%, A/33%, T/33% G/8.5%, A/50%, T/24.5% www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 132 18 In the given diagram of chemical structure of DNA, identify the type of bonding shown by A, B and C. H O H 3′ H HO 5′ H 2C 1 3 N O 9 4 2 2 B O C HO—P== O O== P—OH N H 5 6 3 2 1N 4 3′ 5′ O O H H O Cytosine O N O 1 6 5 2 3 N1 H O 8 9 N 4 N CH2 5′ 3′ Guanine N O H HO Deoxyribose H 3′ O== P—OH H 20 Which of the following is not the correct salient feature of double-helix structure of DNA? H Deoxyribose A O CH2 5′ N 3′ H H2 C O 3 N Adenine O Thymine O 8 N1 NH O 7 5 6 6 4 1 4 5′ 5 2 3′ 3 HO—P== O N N H 3C (a) A–0.34 Å, B–20 Å, C–3.4 Å, D–Phosphate backbone, E–Major groove, F–Minor groove (b) A–3.4 Å, B–20 Å, C–34 Å, D–Sugar backbone, E–Major groove, F–Minor groove (c) A–34 Å, B–20 Å, C–3.4 Å, D–Sugar phosphate backbone, E–Major groove, F–Minor groove (d) A–34 Å, B–20 Å, C–0.34 Å, D–Major groove, E–Minor groove, F–Sugar phosphate bone (a) Two polynucleotide chains have backbone of sugar and phosphate and bases project inside (b) Two chains have antiparallel polarity, i.e. one is 5′→ 3′ and other is 3′→ 5′ (c) Adenine forms three hydrogen bonds with thymine and guanine forms two hydrogen bonds with cytosine (d) The plane of one base pair stacks over the other in double helix in addition to H-bond to confer extra statbility to helical structure 21 The diagram shows an important concept in the genetic implication of DNA. Fill in the blanks A to C. NEET 2013 Proposed by C O (a) A–N-glycosidic bonding, B–Phosphodiester bonding, C–Hydrogen bonding (b) A–N-glycosidic bonding, B–Phosphodiester bonding, C–Covalent bonding (c) A–N-glycosidic bonding, B–Phosphodiester bonding, C–Coordinate bonding (d) A–N-glycosidic bonding, B–Hydrogen bonding, C–Phosphodiester bonding 19 Given the diagram showing Watson and Crick model of DNA structure. Identify the parameters of A, B and C. B Guanine Cytosine C G Thymine Adenine A T C G DNA A mRNA B Protein (a) A–transcription, B–replication, C–James Watson (b) A–translation, B–transcription, C–Erwin Chargaff (c) A–transcription, B–translation, C–Francis Crick (d) A–translation, B–extension, C–Rosalind Franklin 22 In some viruses, the flow of information is in reverse direction, i.e. from RNA to DNA. Can you suggest a simple name to the process? (a) Transcription (b) Transception (c) Reverse transcription (d) Translation 23 The length of DNA in a human cell is about (a) 2.3 m (b) 2.4 m (c) 2.2 m (d) 2.0 m 24 Find out the number of base pairs in E. coli DNA if T its DNA is 1.36 mm long. A A C G T A E G D C G C C T G A Hydrogen bonds 5′ (b) 3 × 106 bp (d) 7 × 106 bp 25 In prokaryotes (such as E. coli) ...A... nucleus is not A F (a) 4 × 106 bp (c) 2 × 106 bp 3′ present, the DNA is not scattered throughout the cell. DNA is ...B... charged and holded by the ...C... charged proteins. This structure in prokaryotes is called ...D... . Choose the correct option for A, B, C and D. (a) (b) (c) (d) A–undefined, B–negatively, C–positively, D–nucleoid A–undefined, B–negatively, C–positively, D–nucleus A–defined, B–negatively, C–positively, D–nucleoid A–defined, B–positively, C–negatively, D–nucleoid www.mediit.in CHAPTER 06 > Molecular Basis of Inheritance 26 Positively charged basic proteins that are found in 133 31 In the given diagram, identify A, B and C. eukaryotes are called (a) histones (c) arginine B A (b) protamine (d) lysine 27 Choose the incorrect pair. (a) Basic amino residues in histones — Lysine and arginine (b) Unit of 8 molecules in histones — Histone octamer (c) Negative charged DNA wrapped around positive charged DNA — Nucleosome (d) Thread-like, colourless unit of structure — Chromatin in nucleus 28 Linker-DNA is attached to (a) H1 (b) H2A JIPMER 2018 (c) H2B (d) H3 29 The packaging of chromatin at higher level requires an additional set of proteins that are collectively referred to as (a) histone proteins (c) basic proteins (b) non-histone proteins (d) acidic packaging proteins 30 The association of histone H1 with a nucleosome indicates NEET 2017 (a) transcription is occurring (b) DNA replication is occurring (c) the DNA is condensed into chromatin fibre (d) the DNA double helix is exposed C Core of histone molecules (a) (b) (c) (d) A–DNA, B–H1 histone, C–Histone octamer A–RNA, B–H1 histone, C–Histone octamer A–DNA, B–H1 histone, C–Histone tetramer A–RNA, B–H1 histone, C–Histone tetramer 32 Lightly stained part of chromatin which remains loosely packed and is transcriptionally active named as (a) (b) (c) (d) euchromatin heterochromatin chromatosome chromonemata 33 Part of chromatin which is densely packed, stain darkly and is transcriptionally inactive is called (a) euchromatin (c) heterochromatin (b) chromatosome (d) chromosome TOPIC 2 ~ The Search for Genetic Material and RNA World 34 Experimental organism of Frederick Griffith was (a) Variola virus (c) Actinomycetes (b) Tuberculosis bacteria (d) Streptococcus pneumoniae 35 What was unique in Griffith’s experiments? (a) DNA was found to be the genetic material (b) RNA was found to be the genetic material (c) Something from dead organisms could change the living cells (d) Viruses can live in bacteria 36 In Griffith experiment, what would be the effect of following conditions on mice? Form of Pneumococcus Injected I. II. III. IV. Effect on Mice Live R-strain Live S-strain Heat-killed S-strain Heat-killed S-strain + live R-strain A B C D Choose the correct option for effect on mice. (a) A–Survived, B–Died, C–Died, D–Survived (b) A–Survived, B–Died, C–Survived, D–Died (c) A–Died, B–Survived, C–Survived, D–Died (d) A–Died, B–Survived, C–Died, D–Died 37 Which scientist experimentally proved that DNA is the sole genetic material in bacteriophage? NEET (Odisha) 2019, 17 (a) Beadle and Tatum (c) Hershey and Chase (b) Meselson and Stahl (d) Jacob and Monod 38 Isotopes used by Hershey and Chase were (a) (c) 32 34 P and 35S P and 31S (b) (d) 35 30 P and 32S P and 32S 39 Bacteriophage nucleic acids were labelled as (in Hershey and Chase experiment) (a) (c) 32 35 P labelled phosphate (b) 3 H labelled H2O S labelled sulphate (d) 14 C labelled CO2 40 Bacteriophage protein coat was labelled by growing E. coli on (a) (b) (c) (d) radioactive sulphur-35 radioactive sulphur-32 radioactive sulphur-30 radioactive phosphorus-32 41 Hershey and Chase concluded that viral infecting agent in their experiment was (a) Protein (c) RNA (b) DNA (d) Both (b) and (c) www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 134 S and 32P to prove that DNA is the genetic material. Their experiments proved that DNA is genetic material because 42 Hershey and Chase used 35 (a) progeny viruses retained 32P but not 35S (b) retention of 32P in progeny viruses indicated that DNA was passed on (c) loss of 35S in progeny viruses indicated that proteins were not passed on (d) All of the above 43 RNA is the genetic material in (a) (b) (c) (d) All bacteria Tobacco Mosaic Viruses (TMV) QB bacteriophage Both (b) and (c) 44 A molecule that can act as a genetic material must fulfill the traits given below, except NEET 2016 (a) it should be able to express itself in the form of ‘Mendelian characters’ (b) it should be able to generate its replica (c) it should be unstable structurally and chemically (d) it should provide the scope for slow changes that are required for evolution 45 Which group present in RNA nucleotide is very reactive and makes RNA liable and easily degradable than DNA? (a) (b) (c) (d) 3–OH′ group at every nucleotide 2–OH′ group on ribose sugar 3–OH′ group on ribose sugar 4–OH′ group on ribose sugar 46 Stability of DNA is due to (a) (b) (c) (d) deoxyribose sugar presence of thymine in place of uracil Both (a) and (b) None of the above 47 Viruses having RNA genome and having shorter lifespan, mutate and evolve faster because (a) (b) (c) (d) RNA is unstable and mutates at faster rate RNA is stable and mutates at faster rate RNA is stable and mutates at slower rate RNA is unstable and mutates at slower rate 48 DNA is dependent on ...A... for synthesis of proteins. DNA and RNA both can function as genetic material. But ...B... being more stable, preferred for the storage of genetic information. For the transmission of genetic information, ...C... is better. Choose the correct option for A, B and C. (a) A–DNA, B–RNA, C–RNA (b) A–RNA, B–DNA, C–RNA (c) A–RNA, B–RNA, C–DNA (d) A–DNA, B–RNA, C–DNA 49 The first genetic material was (a) (b) (c) (d) RNA DNA Both (a) and (b) None of the above 50 Which one of the following is not applicable to RNA? (a) (b) (c) (d) Complementary base pairing CBSE-AIPMT 2015 5′ phosphoryl and 3′ hydroxyl ends Heterocyclic nitrogenous bases Chargaff’s rule 51 Which one of the following option is correct? (a) DNA has evolved from RNA with chemical modifications (b) DNA being complementary double-stranded resists changes by a process of repair (c) RNA being a catalyst is reactive and unstable (d) All of the above TOPIC 3 ~ Replicaton 52 DNA replication is semiconservative. It was shown (a) fungi (b) E. coli (c) Vicia faba (d) algae 53 Who experimentally proved the semiconservative (a) AgCl density gradient (b) CaSO4 density gradient (c) CsCl density gradient (d) KCl density gradient 56 In Meselson and Stahl’s experiment (1958), DNA mode of DNA replication? (a) (b) (c) (d) 55 Heavy DNA can be differentiated from normal DNA by which centrifugation technique? first in extracted from the culture one generation after the transfer from 15 N to 14 N medium had a hybrid (or intermediate) density. Why? Mathew Meselson Franklin Stahl Both (a) and (b) Watson and Crick 54 Name the heavy isotope used by Meselson and Stahl for proving the semiconservative mode of DNA. 14 (a) 15 NH4 Cl (b) (c) 13 NH2 Cl 3 (d) All of these NH3 Cl 2 (a) Because the generation time of E. coli (culture) was about 20 minutes (b) Because it would take 20 minutes for RNA replication (c) Because it would take 20 minutes for replication of DNA to RNA (transcription) (d) Because it would take 20 minutes for translation RNA to protein www.mediit.in CHAPTER 06 > Molecular Basis of Inheritance 57 Given diagram depicts the experiment of Meselson and Stahl. Identify the type of isotopic DNA formed after 40 minutes (A, B, C and D). Generation-I 14N-DNA 135 63 Replication occurs within the small opening of DNA helix referred to as (a) replication fork (c) DNA fork (b) duplication fork (d) RNA fork 64 DNA-dependent DNA polymerases catalyses 15N-DNA polymerisation in which direction? 15N-DNA 40 min 20 min (a) 3′ → 5′ (c) 5′ → 3′ (b) 5′ → 2′ (d) 2′ → 5′ 65 On which strand of DNA, replication is continuous? Generation-II A-DNA B-DNA C-DNA D-DNA (a) (b) (c) (d) 5′ → 3′ polarity strand 3′ → 5′ polarity strand 3′ → 2′ polarity strand 3′ → 4′ polarity strand 66 Identify A, B and C strands. 5′ 3′ (a) (b) (c) (d) A–14 N-DNA, B–15 N-DNA, C–14 N-DNA, D–15 N-DNA A–14 N-DNA, B–15 N-DNA, C–14 N-DNA, D–14 N-DNA A–14 N-DNA, B–14 N-DNA, C–15 N-DNA, D–15 N-DNA A–14 N-DNA, B–15 N-DNA, C–15 N-DNA, D–15 N-DNA C 58 Similar experiments like Meselson and Stahl was performed by Taylor in 1958. The experimental organism of Taylor was (a) Vicia faba (c) E. coli (b) Fungi (d) Protista 59 Radioisotope used by Taylor in his experiment was (a) iron (c) thymidine (b) titanium (d) copper 3′ 5′ (a) A–Continuous strand, B–Discontinuous strand, C–Template strand (b) A–Leading strand, B–Lagging strand, C–Parental strand (c) A– 5′−3′ strand, B– 3′−5′ strand, C–Parental strand (d) All of the above (a) primase (c) DNA topoisomerase (b) polymerase (d) SSBPs 68 During DNA replication, okazaki fragments are used to elongate 61 DNA polymerisation rate of DNA polymerase is (b) 2000 bp/s (d) 5000 bp/s 62 For long DNA molecules, the two strands of DNA cannot be separated in its entire length due to the requirement of (a) (b) (c) (d) B Newly synthesised strands JIPMER 2019 DNA dependent DNA independent RNA dependent RNA independent (a) 1000 bp/s (c) 3000 bp/s 3′5′ 5′ 67 During DNA replication, supercoiling is relaxed by 60 DNA polymerase is (a) (b) (c) (d) 3′ A enzymes high energy RNA phosphate and nucleotide NEET 2017 (a) The leading strand towards replication fork (b) The lagging strand towards replication fork (c) The leading strand away from replication fork (d) The lagging strand away from the replication fork 69 Deoxyribonucleoside triphosphate serve dual purposes. The purposes are (a) act as substrate and decrease reaction rate (b) provide energy for polymerisation and act as substrate (c) decrease reaction rate and provide energy for polymerisation (d) Synthesise RNA primer and decrease reaction rate www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 136 TOPIC 4~ Transcription 70 Which one of the following is wrongly matched? Codes CBSE-AIPMT 2014 (a) Transcription – Writing information from DNA to t RNA (b) Translation–Using information in mRNA to make proteins (c) Repressor protein – Binds to operator to stop enzyme synthesis (d) Operon – Structural genes, operator and promoter 71 Why both the strands of DNA are not copied during transcription? (a) Because RNA molecule with different sequences will be formed (b) Because RNA molecule with same sequences will be formed (c) Because RNA molecule with identical sequences will be formed (d) Because DNA molecule with different sequences will be formed 72 If both the strands copied during transcription, then what will happen? 73 What will happen if the double-stranded RNA is produced during transcription? (a) This would prevent RNA from being translated into protein (b) This would not prevent RNA from being translated into protein (c) There will be the continuous synthesis of RNA (d) Double-stranded RNA will have lower stability. It will be degraded very fastly 74 Which strand of DNA works as template strand? (a) 5′ – 3′ polarity strand (b) 3′ – 5′ polarity strand (c) Both (a) and (b) (d) None of these 75 The strand which do not code for anything is called (a) coding strand (c) template strand (b) non-coding strand (d) antisense strand 76 In given diagram find out Transcription start site 5 5′ A. Promoter site C. Terminator site E. Coding strand A 5 5 5 5 B 1 1 4 4 C 4 4 1 1 D 2 3 2 3 E 3 2 3 2 77 If the coding strand has the sequence 5 ′–ATCGATCG–3′ then find out the sequence of non-coding strand. (a) (b) (c) (d) 3′ − TAGCTAGC − 5 ′ 5′− TACGTACG − 3 ′ 5′− UAGGUACG − 3 ′ 5′− UACFUACG − 3 ′ 78 AGGTATCGCAT is a sequence from the coding strand of a gene. What will be the corresponding sequence of the transcribed mRNA? NEET 2018 (a) ACCUAUGCGAU (c) AGGUAUCGCAU (b) UGGTUTCGCAT (d) UCCAUAGCGUA 79 Which of the following mRNA can be transcripted? (a) The segment of DNA would be coding for two different proteins (b) Two RNA will be produced simultaneously complementary to each other (c) There will be formation of double helical RNA (d) All of the above 3′ (a) (b) (c) (d) 4 2 5′ B. Structural gene D. Template strand (b) UAA.UAV.UGG (d) UGA.UUV.UGG 80 What will be the sequence of mRNA produced by the following stretch of DNA? 3'–ATGCATGCATGCATG–5' Template strand 5'–TACGTACGTACGTAC–3' Coding strand (a) 3' – AUGCAUGCAUGCAUG–5' NEET (Odisha) 2019 (b) 5' – UACGUACGUACGUAC–3' (c) 3' – UACGUACGUACGUAC–5' (d) 5'– AUGCAUGCAUGCAUG–3' 81 Promoter and terminator flanks the (a) house-keeping gene (c) recon (b) structural gene (d) transcription unit 82 Choose the incorrect pair. (a) Promoter (b) Terminator — Define the end of transcription process — Binding site for RNA polymerase (c) Cistron — Segment of RNA coding for a polypeptide (d) Regulatory genes — Do not code for any RNA or protein 83 Identify the correct pair of mRNA type and its 1 3 JIPMER 2018 (a) AUG.UGA.UUU (c) UAG.UGA.UUV 3′ function. (a) Messenger RNA — Provides the template (b) Transfer RNA — Brings amino acids and reads genetic code (c) Ribosomal RNA — Plays catalytic role during translation (d) All of the above www.mediit.in CHAPTER 06 > Molecular Basis of Inheritance 84 Which of the following RNAs should be most abundant in animals cell? (a) rRNA (b) tRNA NEET 2017 (c) mRNA (d) miRNA 85 DNA-dependent RNA polymerase catalyses 137 92 In splicing, the sequences which are kept and those which are removed, respectively, are (a) exons and introns (c) exons and cistrons (b) introns and exons (d) introns and cistrons transcription on one strand of the DNA which is called the NEET 2016 93 Spliceosomes are not found in cells of (a) template strand (c) alpha strand 94 Name the nucleotide added to 5′ end of hnRNA in (b) coding strand (d) anti-strand of all types of RNA (mRNA, tRNA and rRNA)? DNA-dependent RNA polymerase DNA-dependent DNA polymerase RNA-dependent RNA polymerase RNA-dependent DNA polymerase (b) Elongation (d) Aminoacylation 88 What initiation and termination factors are involved in transcription in eukaryotes? NEET (Odisha) 2019 (b) α and β, respectively (d) α and σ, respectively 89 3′ (A) RNA polymerase (B) (C) 5′ 5′ 3′ RNA Polymerase Rho factor 3′ 5′ RNA σ Terminator Identify A, B and C. AIIMS 2019 (a) A–Elongation, B–Termination, C–Initiation (b) A–Initiation, B–Termination, C–Elongation (c) A–Initiation, B–Elongation, C–Termination (d) A–Termination, B–Elongation, C–Initiation 90 In bacteria, transcription and translation takes place in the same compartment. Why? (a) No separation of cytosol and nucleus (b) mRNA does not require any processing to become active (c) Both (a) and (b) (d) Due to the presence of nucleus 91 In the process of transcription in eukaryotes, the RNA polymerase-I transcribes (a) (b) (c) (d) 96 What happens in the tailing process of transcription? (a) (b) (c) (d) Adenylate residues added at 5′ end of RNA Adenylate residues added at 3′ end of RNA Guanylate residues added at 5′ end of RNA Guanylate residues added at 3′ end of RNA 97 Fully processed hnRNA to undergo translation is called (b) rRNA (c) tRNA (d) sRNA 5′ 3′ 5′ 3′ A Capping B Cap 5′ 3′ (b) Modified C at 5′ (d) Poly-C (a) Poly-A tail (c) 7 mG transcription in eukaryotes. Identify A, B, C and D. 3′ ρ Ethyl cytosine triphosphate Ethyl guanosine triphosphate Methyl guanosine triphosphate Methyl cytosine triphosphate 98 The following diagram refers to the process of Sigma factor RNA (a) (b) (c) (d) (a) mRNA 3′ 5′ DNA helix 5′ Promoter σ (d) bacteria JIPMER 2018 catalysed by RNA polymerase only? (a) σ and ρ, respectively (c) β and γ, respectively NEET 2017 (c) animals 95 Which is present at 5′ end of eukaryotic mRNA? 87 In prokaryotes, which process of transcription is (a) Initiation (c) Termination (b) fungi capping. 86 In bacteria, which enzyme catalyses the transcription (a) (b) (c) (d) (a) plants NEET (Odisha) 2019 mRNA with additional processing, capping and tailing tRNA, 5 srRNA and snRNAs rRNAs-28 S, 18 S and 5.8 S precursor of mRNA, hnRNA mG ppp C 5′ m Gppp 5′ RNA splicing mG ppp m Gppp 5′ 5′ Messenger RNA (mRNA) 3′ mRNA Polyadenylation or tailing 3′ D 3′ (a) A–RNA polymerase-II, B–Exon, C– Intron, D–Poly-A tail (b) A–RNA polymerase-III, B–Intron, C– Exon, D–Poly-A tail (c) A–RNA polymerase-II, B–Intron, C– Exon, D–Poly-A tail (d) A–RNA polymerase-III, B–Intron, C– Exon, D–Poly-G tail 99 Choose the correct option. (a) Splicing represent the dominance of RNA world (b) The presence of introns is reminiscent of antiquity (c) Split gene arrangements represent an ancient feature of the genome (d) All of the above www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 138 TOPIC 5 ~ Genetic Code 100 Genetic code 112 From the following, identify the correct combination (a) is a relationship between sequence of DNA or mRNA to polypeptide (b) triplet base on mRNA (c) determines the sequence of amino acid in polypeptide (d) All of the above 101 In order to code for all the 20 amino acids, the code should be made up of three nucleotides. This statement was suggested by (a) Har Gobind Khorana (c) Marshall Nirenberg (b) George Gamow (d) Servo Ochoa molecules with well-defined combination of bases (homopolymers and copolymers) to develop genetic code? (b) Har Gobind Khorana (d) Nirenberg 103 Who used cell free system for protein synthesis? (a) Marshall Nirenberg (c) Khorana (b) Ochoa (d) Gamow 104 Polynucleotide phosphorylase enzymes are also called (b) Servo Ochoa enzymes (a) Crick et. al enzymes (c) James Watson enzymes (d) Mendel enzymes 105 How many codons codes for amino acids? (a) 25 (b) 50 (c) 61 (d) 60 106 The genetic codes of arginine are (a) CGU, CGC, CGA (c) AGU, AGC, AAC AIIMS 2019 (b) CAU, CAC, CAA (d) GAU, GAC, GAA 107 Codons of glycine are AIIMS 2018 (a) CCU, CCC, CCA, CCG (b) CGU, CGC, CGA, CGG (c) GGU, GGC, GGA, GGG (d) ACU, ACC, ACA, ACG (b) histidine (d) alanine JIPMER 2019 (b) UAC (c) UAG (d) UGA 110 The one aspect, which is not a salient feature of genetic code is, its being (a) degenerate (c) universal (b) ambiguous (d) specific 111 Codons are non-ambiguous, which means that one codon codes for (a) (b) (c) (d) more than one amino acid two amino acids Only one amino acid non-sense amino acid 114 Which of the following features of genetic code does allow bacteria to produce human insulin by recombinant DNA technology? NEET 2019 (a) Genetic code is redundant (b) Genetic code is nearly universal (c) Genetic code is specific (d) Genetic code is not ambiguous 115 The relationship between genes and DNA are best understood by (a) (b) (c) (d) mutation recombination enzymatic synthesis of amino acid enzymatic synthesis of codons 116 Sickle-cell anaemia is a classical example of point mutation in which valine amino acid comes in place of (a) glutamate (b) tryptophane (c) alanine (d) guanine no change in the reading frame of following mRNA? NEET 2019 5′–AACAGCGGUGCUAUU–3 ′ 109 Which of the following is not a stop condon? (a) UAA (a) one amino acid has more than one code triplet (b) one amino acid has only one code triplet (c) codons which specify the same amino acids differ only in the third base of the triplet (d) Both (a) and (c) 117 Under which of the following conditions will there be 108 The codon AUG codes for (in eukaryotes) (a) methionine (c) tryptophan NEET (Odisha) 2019 (a) Universal, non-ambiguous, overlapping (b) Degenerate, overlapping, commaless (c) Universal, ambiguous, degenerate (d) Degenerate, non-overlapping, non-ambiguous 113 Degeneracy refers to 102 Who developed the technique of synthesising RNA (a) Crick et. al (c) Matthaei of salient features of genetic code. (a) Deletion of G from 5th position (b) Insertion of A and G at 4th and 5th positions, respectively (c) Deletion of GGU from 7th, 8th and 9th positions (d) Insertion of G at 5th position 118 If there are 999 bases in an RNA that codes for a protein with 333 amino acids and the base at position 901 is deleted such that the length of the RNA becomes 998 bases, how many codons will be NEET 2017 altered? (a) 1 (c) 33 (b) 11 (d) 333 119 Which mutation of the genetic bases gives the proof that codon is triplet and reads in a contagious manner? (a) Frameshift mutation (c) Both (a) and (b) (b) Point mutation (d) Inversion mutation www.mediit.in 139 CHAPTER 06 > Molecular Basis of Inheritance 120 The presence of an adapter molecule that would on one hand read the code and on other hand would bind to specific amino acids was postulated by (a) Francis Crick (c) Rosalind Franklin (b) James Watson (d) Griffith 121 Before the genetic code was postulated, the tRNA was called (a) (b) (c) (d) rRNA (ribosomal RNA) mRNA (messenger RNA) sRNA (soluble RNA) sRNA (sedimentary RNA) (a) A–Variable arm, B–D-loop, C–T-loop, D–Anticodon arm, E–Codon, F–Variable arm (b) A–Amino acid arm, B–T-loop, C–Variable arm, D–Anticodon arm, E–Codon, F–D- loop (c) A–Amino acid arm, B–T-loop, C–Anticodon loop, D–Anticodon, E–Codon, F–D-loop (d) A–Amino acid arm, B–T-loop, C–Anticodon loop, D–Anticodon, E–Codon, F–Variable arm 123 Choose the incorrect option for tRNA molecule. 122 Study the given figure and identify A to F. Tyr A (a) It has an anticodon loop that has bases complementary to the code (b) It has an amino acid acceptor end to which it binds to amino acids (c) tRNA are not specific for each amino acid (d) tRNA looks like a clover leaf 124 tRNA is a compact molecule which looks like (a) M-shaped (b) P-shaped (c) L-shaped (d) K-shaped F 125 RNA binds to mRNA through B A U U G A C JIPMER 2019 (a) anticodon loop (b) T ψ C loop (c) amino acid binding loop (d) D-loop C D E mRNA 126 Removal of RNA polymerase-III from nucleoplasm will affect the synthesis of 3¢ (a) tRNA CBSE-AIPMT 2012 (b) hnRNA (c) mRNA (d) rRNA TOPIC 6 ~ Translation 127 The process of polymerisation of amino acids to form a polypeptide is (a) transcription (c) translation (b) replication (d) polymerisation 128 Many ribosomes may associate with a single mRNA to form multiple copies of a polypeptide simultaneously. Such strings of ribosomes are termed as NEET 2018, 16 (a) plastidome (c) polysome (b) polyhedral bodies (d) nucleosome 129 In the protein synthesis, tRNA carrying the amino acid enters from which site of the ribosome? (a) A-site (c) Anticodon site (b) P-site (d) R-site 130 The order and sequences of amino acids are defined by the sequences of the bases in (a) rRNA (b) mRNA (c) tRNA (d) All of these 131 Which of the following enzymes are required in protein synthesis? I. Ligase II. Permease IV. Ribozyme III. Endonuclease V. RNA polymerase VI. Peptidyl transferase VII. Amino acid activating enzyme Choose the correct option. (a) IV, VI and VII (c) II, III, IV and V (b) I, II and III (d) All of these 132 Which among the following process occur(s) during charging or aminoacylation of tRNA? (a) (b) (c) (d) Activation of amino acids in the presence of ATP Linking of amino acids to their cognate tRNA Both (a) and (b) None of the above 133 The cellular factory responsible for the synthesis of proteins is (a) (b) (c) (d) mitochondria endoplasmic reticulum Golgi body ribosome 134 Which of the following rRNAs act as structural RNA as well as ribozyme in bacteria? (a) 5 srRNA (c) 23 srRNA NEET 2016 (b) 18 srRNA (d) 5.8 srRNA 135 UTRs present on mRNA refer to (a) (b) (c) (d) Untranscribed regions at both 5′ end and 3′ end Untranslated regions at 5′ end Untranslated regions at both 5′ end and 3′ end Untranslated regions at 3′ end www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 140 136 For initiation, the ribosomes binds to the ...A... at the start codon and ...B... is recognised by the ...C... . Choose the correct option for A, B and C. (a) (b) (c) (d) A–mRNA, B–AUG, C–initiator tRNA A–mRNA, B–AUG, C–tRNA A–rRNA, B–AUG, C–tRNA A–rRNA B–AUG, C–initiator mRNA 140 Study the diagram given below of translation and choose the correct option for labels A, B, C, D and E. Gly Leu Tyr Growing polypeptide chain Ser Leu A — Kind to stop codon for terminating translation (c) Translational unit — Sequence of RNA with start codon only (d) Elongation phase — Ribosome moves from codons to codons along mRNA 138 For the given DNA sequence 3′–TACATGGGTCCG–5′. Choose the correct sequential code of tRNA anticodon. I. UAC II. AUG III. GGC IV. CCA (a) I, II, III and IV (c) I, III, II and IV (b) II, III, IV and I (d) II, I, IV and III 139 RNA molecule I II III IV Anti-codon pairing UCA AUG AUU AUC Which of the following tRNA molecules does not exist? (b) II and III (c) III and IV (d) IV and I G Release factor G (b) B Ser E Val tRNA tRNA A Required for efficient translation process A — Asn U Untranslated regions Transferase enzyme forming peptide bond U (a) A-site (Amino acyl tRNA site) Gly 137 Choose the incorrect pair. (a) I and II P-site (Peptidyl tRNA site) CGU CAA Amino acid tRNA complex Large ribosomal subunit C U C U UGGGU C CGC A G U U A AU U U C A U C D C mRNA Ribosome A B (a) Charged/ Uncharged tRNA Aminoacylated tRNA Small ribosomal subunit C D E 5′ end 3′ end Glycine (b) Uncharged tRNA Charged/Aminoacy- 5′ end 3′ end lated tRNA Alanine (c) Uncharged tRNA Charged/Aminoacy- 3′ end 5′ end lated tRNA Glycine (d) Uncharged tRNA Charged/Aminoacy- 5′ end 3′ end lated tRNA Lysine 141 Termination of protein synthesis or translation requires (a) Both stop signal and starting codon (b) Both starting codon and release factor (c) Both release factor and stop codon (d) GUG and AUG codon TOPIC 7 ~ Regulation of Gene Expression 142 The regulation of gene expression in eukaryotes can be exerted at I. transcriptional level. II. processing level. III. transport of mRNA (from nucleus to cytoplasm). IV. translational level. Choose the correct combination to complete the statement. (a) I and II (c) III and IV (b) II and III (d) All of these 143 In prokaryotes, control of the rate of ...A... is the pre-dominant site for the control of gene expression. In a transcription unit, the activity of ...B... at a given promoter is in turn regulated by interaction with ...C... proteins, which affects its ability to recognise the start sites. Complete the statement filling the correct options in given blanks. (a) A–RNA replication, B–DNA polymerase, C–accessory (b) A–transcriptional initiation, B–RNA polymerase, C–accessory (c) A–translational initiation, B–RNA polymerase, C–accessory (d) A–DNA replication, B–RNA polymerase, C–accessory 144 Positively regulatory proteins are called (a) (b) (c) (d) activator repressors necessary proteins accessory proteins www.mediit.in 141 CHAPTER 06 > Molecular Basis of Inheritance 145 The accessibility of the promoter regions of prokaryotic DNA is (in many cases) regulated by the interaction of proteins with the sequences termed as (a) regulator (c) operator (b) promoter (d) structural genes 146 An operon is considered to regulate a (a) translational unit (c) protein unit (b) genetic unit (d) enzymatic unit 153 Lactose is a substrate for 147 1st operon model was (b) lac operon (d) val operon (a) trp operon (c) his operon 148 Select the correct match. (a) (b) (c) Matthew Meselson and F Stahl Alfred Hershey and Martha Chase Alec Jeffreys (d) Francois Jacob and Jacques Monod : NEET 2018 Pisum sativum TMV : : : Streptococcus pneumoniae Lac operon 149 Number of regulatory and structural genes present in (a) (b) (c) (d) galactosidase α-galactosidase β-galactosidase γ-galactosidase 154 Lactose is transported into cells through (a) (b) (c) (d) β-galactosidase permease transacetylase transferase 155 The given diagram of the lac operon showing an operon of inducible enzymes. Identify components and enzymes (A, B, C, D and E). lac operon are (a) one and two (c) one and one (a) A–Regulatory gene, B–Promoter, C–Operator, D–Structural gene (b) A–Regulatory gene, B–Promoter, C–Structural gene, D–Operator (c) A–Regulatory gene, B–Structural gene, C–Pormoter, D–Operator (d) A–Regulatory gene, B–Structural gene, C–Operator gene, D–Promoter gene (b) one and three (d) three and one i p o z y a 150 Gene regulation governing lactose operon of E. coli that involves the lac i gene products is Transcription lac mRNA mRNA CBSE-AIPMT 2015 (a) positive and inducible because it can be induced by lactose (b) negative and inducible because its repressor protein prevents transcription (c) negative and repressible because its repressor protein prevents transcription (d) feedback inhibition because excess of β-galactosidase can switch off transcription 151 Which enzyme(s) will be produced in a cell in which there is a non-sense mutation in the lac y-gene? (a) β-galactosidase (b) Lactose permease (c) Transacetylase (d) Lactose permease and transacetylase NEET 2013 i mRNA p C (a) Operator (c) Promoter JIPMER 2018 (b) Inducer (d) Structural gene 157 Why glucose and galactose cannot act as an inducer C o B (a) A–Galactosidase, B–Permease, C–Transacetylase, D–Repressor protein, E–Inducer (lactose) (b) A–Galactosidase, B–Permease, C–Transacetylase, D–Inducer (lactose), E–Repressor protein (c) A–Galactosidase, B–Transacetylase, C–Permease, D–Repressor protein, E–Inducer (lactose) (d) A–Permease, B–Transacetylase, C–-Galactosidase, D–Repressor protein, E–Inducer (lactose) attached? operon. B A E 156 To, which of the following, repressor protein is 152 Identify A, B, C and D in the given diagram of a lac A Translation Enzymes D for lac operon? z y Repressor RNA polymerase operator D compound a (a) (b) (c) (d) Because they cannot bind with the repressor Because they can bind with the repressor Because they can bind with the operator Because they can bind with the regulator Repressor www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 142 TOPIC 8 ~ Human Genome Project 158 Which of the following option is true for Human Genome Project (HGP)? (a) It was launched in the year 1990 and was called mega project (b) Total estimated cost of the project would be 9 billion US dollars (c) It aims to identify all 20000-25000 genes in human DNA (d) All of the above 159 Human genome project was co-ordinated by (a) (b) (c) (d) Europian Department of Energy US Department of Energy National Institute of Health Both (b) and (c) 160 Identify the incorrect option regarding human genome project. (a) It was completed in 2003 (b) It aims to determine the sequence of 3 billion chemical base pairs and store it in data bases (c) It associated ethical legal and social issues arising from the project (d) It is not associated with non-human organisms DNA sequences 161 Gene library or DNA library has the collection of (a) DNA and RNA (b) Any one type of gene of organism (c) cDNA (d) All possible genes are organisms AIIMS 2019 162 Which among the following are non-human model whose genome are sequenced? (a) Caenorhabditis elegans (c) Plants (rice and Arabidopsis) (b) Drosophila (d) All of these 163 Identify the incorrect pair. (a) Expressed sequence tags — Genes that are express as RNA — Sequencing genome with (b) Sequence annotation coding sequences (c) Automated DNA sequences — Work on the principle developed by Frederick Sanger (d) None of the above 164 How genetic and physical maps were generated in HGP? (a) (b) (c) (d) By using DNase By using RNase By using restriction endonuclease By using automated DNA sequences 165 To make chromosomal studies easier, chromosomes are classified into certain groups. So, the chromosome JIPMER 2019 number 21, 22 and Y are listed in (a) A (b) D (c) E (d) G 166 Exact number of nucleotides contained in human genome, revealed by human genome project are (a) 3164.7 million bp (c) 3162.7 million bp (b) 3163.7 million bp (d) 3160.7 million bp 167 Average gene consists of ...A... bases, but their size vary greatly, with the largest known human gene being ...B... with ...C... bases. Complete the statement filling the correct option in the given blanks. (a) (b) (c) (d) A–3000 bases, B–dystrophin, C–2.4 million A–2000 bases, B–dystrophin, C–2.4 million A–1000 bases, B–dystrophin, C–2.0 million A–3000 bases, B–dystrophin, C–2.0 million 168 Percentage of similarity between the nucleotides of two individuals is (a) 98% (b) 99% (c) 99.9% (d) 99.8% 169 Total percentage of genes, which codes for proteins is (a) 2% (b) 3% (c) 4% (d) 5% 170 Repetitive DNA make up very large portion of human genome and are important for studying (a) chromosome structure (b) chromosome dynamics (d) All of these (c) evolution 171 Choose the incorrect option. (a) HGP is closely associated with bioinformatics (b) HGP will help in developing new ways to diagnose, treat and some day prevent disorders affecting humans (c) Fragment sequenced during HGP are done by method developed by Frederick Sanger (d) Repetitive DNA sequences are stretches of DNA repeated 2-3 times in a DNA sequence 172 SNP–Single Nucleotide Polymorphisms is (a) location on RNA where the single base differs (b) location on proteins where the single base differs (c) location on genome where the single base of DNA differs (d) location on genome where many bases of DNA differs 173 SNPs can be used for (a) finding chromosome locations for disease associated sequences (b) tracing human history (c) evolution (d) All of the above www.mediit.in 143 CHAPTER 06 > Molecular Basis of Inheritance TOPIC 9 ~ DNA Fingerprinting 174 DNA fingerprinting involves identifying the differences in some specific regions in DNA sequence called (a) (b) (c) (d) non-repetitive DNA coding DNA non-coding DNA repetitive DNA (b) non-satellite DNA (d) intronic DNA 176 Satellite DNA is important because it CBSE-AIPMT 2015 (a) codes for proteins needed in cell cycle (b) shows high degree of polymorphism in population and also the same degree of polymorphism in an individual, which is heritable from parents to children (c) does not code for proteins and is same in all members of the population (d) codes for enzymes needed for DNA replication 177 Basis of DNA fingerprinting high degree of polymorphism in sequences low degree of polymorphism in sequences intermediate degree of polymorphism in sequences sequences show no polymorphism 178 The technique of DNA fingerprinting was initially developed by (a) Lalji Singh (c) Frederick Sanger (b) Alec Jeffreys (d) Jacob and Monod 179 Alec Jeffreys used a satellite DNA as probe that shows very high degree of polymorphism. It was called as (a) (b) (c) (d) Short Number of Tandem Repeats (SNTRs) Large Number of Tandem Repeats (LNTRs) Variable Number of Tandem Repeats (VNTRs) All of the above 180 VNTR belongs to the class of satellite DNA referred to as (a) (b) (c) (d) microsatellite DNA minisatellite DNA megasatellite DNA repetitive DNA (b) 0.2-10 kb (d) 0.4-15 kb increased by major peaks during density gradient centrifugation. The other small peaks are referred to as (a) (b) (c) (d) (a) 0.1-20 kb (c) 0.3-30 kb 182 The sensitivity of DNA fingerprinting can be 175 The bulk of DNA (other than repetitive) forms the (a) satellite DNA (c) exonic DNA 181 VNTR varies in size from (a) (b) (c) (d) using intron sequences using exon sequences using polymerase chain reactions All of the above 183 Southern blotting technique involves the transfer of DNA from (a) (b) (c) (d) gel to membrane membrane to gel solution to gel gel to solution 184 Steps in DNA fingerprinting are Isolation of DNA ↓ Digestion of DNA by (A) ↓ Separation of DNA by (B) ↓ Transfering of DNA to (C) ↓ DNA hybridisation using (D) ↓ Detecting of hybridised DNA by (E) Complete the accompanying A, B, C, D and E in the flowchart are (a) A–Restriction endonuclease, B–Electrophoresis, C–Nitrocellulose or nylon, D–Labelled VNTR probe, E–Autoradiography (b) A–Electrophoresis, B–Restriction endonuclease, C–Nitrocellulose or nylon, D–Labelled VNTR probe, E–Autoradiography (c) A–Restriction endonuclease, B–Electrophoresis, C–Labelled VNTR probe, D–Nitrocellulose or nylon, E–Autoradiography (d) A–Restriction endonuclease, B–Electrophoresis, C–Nitrocellulose or nylon, D–Autoradiography, E–Labelled VNTR probe www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 144 NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Directions (Q. No. 185-199) In each of the following questions, a statement of Assertion (A) is given by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 193 Assertion (A) hnRNA is larger than mRNA. 194 195 185 Assertion (A) DNA acts as a genetic material in all organisms. Reason (R) It is a double-stranded biomolecule in most organisms. 196 186 Assertion (A) DNA has two chains having antiparallel polarity. Reason (R) In one chain of DNA at one end has a free phosphate moiety 5′ end of ribose sugar and at other end the ribose has a free 3′ OH group. 197 198 187 Assertion (A) Adenine cannot pair with cytosine. Reason (R) Adenine and cytosine do not have complementarity between their respective hydrogen donor and hydrogen acceptor sites. 188 Assertion (A) Histones are basic in nature. Reason (R) These are rich in the amino acids lysine and arginine. 199 Reason (R) hnRNA has non-coding introns which are not required for translation. Assertion (A) Polycistronic mRNA is capable of forming a number of different polypeptide chains. Reason (R) Polycistronic mRNA has terminator codons. Assertion (A) In transcription, the strand with 3′ → 5′ polarity acts as the template strand. Reason (R) The enzyme RNA polymerase catalyses the polymerisation in only one direction, i.e. 5′ → 3′. Assertion (A) In eukaryotes, transcription occurs in nucleus. AIIMS 2019 Reason (R) In bacteria, transcription and translation occur in cytoplasm. Assertion (A) The genetic code is degenerate. Reason (R) Most amino acids are coded by more than one codon. Assertion (A) mRNA has some untranslated regions that are not translated. Reason (R) UTRs are required for efficient translation. Assertion (A) DNA fingerprinting is very well-known for its application in paternity testing in case of disputes. Reason (R) It employs the principle of DNA polymorphism. 189 Assertion (A) Heterochromatin is transcriptionally inactive. Reason (R) It is densely packed. 190 Assertion (A) Viruses having RNA genome and shorter lifespan, mutate and evolve faster. Reason (R) RNA is unstable and thus mutates faster. 191 Assertion (A) Replication on one strand of DNA is continuous and on another it is discontinuous. Reason (R) The DNA polymerase works in 3′ → 5′ direction. 192 Assertion (A) Replication and transcription occur in the nucleus, but translation takes place in the cytoplasm. Reason (R) mRNA is transferred from the nucleus into cytoplasm where ribosomes and amino acids are available for protein synthesis. II. Statement Based Questions 200 Read the following statements. I. A purine is heterocyclic, 9-membered double ring structure with nitrogen at 1st, 3rd, 7th and 9th positions. II. A pyrimidine is heterocyclic, 6-membered single ring structure with nitrogen at 1st and 3rd positions. III. Purine nucleosides have1′-9 glycosidic linkage whereas pyrimidine nucleosides have1′-1-glycosidic linkage. IV. Two nucleosides are linked by 3′-5′ phosphodiester linkage to form a dinucleotide. V. Ribose sugar can be represented as C5 H10 O4 whereas deoxyribose sugar can be represented as C5 H10 O5 . Which of the above statement(s) is/are correct? (a) Only I (c) III, IV and V (b) I, II, III and IV (d) IV and V www.mediit.in 145 CHAPTER 06 > Molecular Basis of Inheritance 201 Choose the incorrect statement. (a) A nucleotide contains ribose sugar or deoxyribose sugar (b) A nucleotide contains pyrimidine bases and purine bases (c) A nucleotide contains protein, carbohydrates and fats (d) A phosphate group is present in a nucleotide 202 Which of the following statements about Griffith’s experiment are correct? I. S-strain have mucus (polysaccharide) coat. II. S-strain are virulent is cause pneumonia infection, while R-strain do not. III. Transforming principle is associated with genetic material of R-strain. IV. Transformation of R-strain into S-strain can take place in a test tube. (a) I and III (c) I, II and IV (b) III and IV (d) II, III and IV 203 Choose the correct statements about biochemical characterisation of transforming principle in Griffith’s experiment. I. It was done by Oswald Avery, Colin MacLeod and Maclyn McCarty. II. Scientists purified biochemicals (proteins, DNA, RNA, etc.) from heat killed S-cell. III. It was seen that DNA alone from S-bacteria caused R-bacteria to become transformed . IV. Proteases and RNases did not affect transformation. (a) (b) (c) (d) I and II III and IV I and III All statements are correct 204 Which of the following statements about Hershey and Chase experiment are correct? I. Sulphur is present in proteins, but not in DNA. II. Phosphorus is present in DNA, but not in proteins. III. 32P will end up in the supernatant after centrifugation. IV. Progeny generation of T 2 -bacteriophage contains 32P. (a) I and II (c) III and IV (b) II and III (d) I, II and IV 205 Choose the incorrect statement(s) about the experiment conduted by Meselson and Stahl’s that (a) equal amount of light DNA and hybrid DNA was observed in E. coli culture after two generations (b) the generation time of E. coli culture was 40 minutes (c) the equal amount of light DNA and hybrid DNA was observed in E. coli culture after three generations (d) Both (a) and (b) 206 J Watson and F Crick proposed the double helix model of DNA. Choose the correct statements with respect to their model of DNA. I. Based on X-ray diffraction of DNA produced by M Wilkins and R Franklin. II. One of the hall marks of their proposition was base pairing between the two strands of polynucleotide chains. III. The two polynucleotide chains are antiparallel to each other . IV. Based on Chargaff’s rule(A + G / T + C = 1) Choose the correct option. (a) (b) (c) (d) I, II and III II, III and IV I, II, III and IV All of the above 207 Choose the incorrect statement about the semiconservative scheme of DNA replication. (a) Watson and Crick proposed the scheme for replication of DNA in 1953 (b) The scheme suggested that the two strands would separate and act as a template for the synthesis of new complementary strands (c) Griffith proposed the scheme of semiconservative DNA replication (d) After the completion of replication, each DNA molecule would have one parental and one newly synthesised strand 208 Arrange the following events of replication of DNA. I. Bonds between complementary bases breaks. II. Bonds between complementary bases forms. III. DNA molecules uncoils. IV. Opposite strands separates. V. Sugar phosphate bonds forms. VI. Free nucleotides align with the complementary nucleotides on each strand. Choose the correct option. (a) (b) (c) (d) VI → I → III → IV → V → II III → VI → I → IV → V → II I → III → VI → IV → II → V III → I → IV → VI → II → V 209 Choose the correct statements about DNA replication. I. Discontinuously synthesised fragments are later joined by the enzyme DNA ligase. II. There is a definite region in E. coli DNA where the replication originates, known as origin of replication. III. In eukaryotes, the replication of DNA takes place at S-phase of the cell cycle. IV. Failure of cell division after DNA replication results in polyploidy. V. E. coli having 4.6 × 106 bp completes DNA replication within 38 minutes. (a) I and II (c) I and V (b) III and IV (d) All of these www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 146 210 Choose the correct statement. (a) The regions of transcriptional units are promoter, structural gene and terminator (b) The region of transcriptional units are exon, intron and cistron (c) The region of DNA where transcription stops is present on promoter (d) The terminator codes for enzyme or protein 211 Consider the following statements. I. The presence of a promoter in a transcription unit defines the template and coding strands. II. DNA-dependent RNA polymerase catalyse the polymerisation in only one direction that is 5′→3′. III. The DNA sequence coding for tRNA or rRNA molecules also define a gene. IV. Regulatory sequences are loosely defined as regulatory genes and these sequences do not code for any RNA or protein. Choose the correct statements. (a) I and IV (c) II and IV (b) I, II and III (d) I, II, III and IV 212 Which one of the following statement is incorrect? (a) Structural gene in transcription unit is monocistronic in eukaryotes and polycistronic in bacteria (b) Monocistronic genes in eukaryotes are split (c) Exons are non-coding and introns are coding sequences of gene (d) Intervening sequences do not appear in mature or processed RNA 213 Choose the correct statement(s). (a) The factors required for the synthesis of protein are initiation code and ribosomes (b) The factors required for the synthesis of protein are GTP, ATP and amino acid pool (c) The factors required for the synthesis of protein are tRNA and mRNA (d) All of the above 214 Consider the following statements. I. rRNA provides the template for synthesis of proteins. II. tRNA brings amino acids and reads the genetic code. III. RNA polymerase binds to promoter and initiates transcription. IV. A segment of DNA coding for polypeptide is called intron. Which of the statements given above are correct? (a) I and III (b) I and II (c) I, II and III (d) II and III 215 Following are the stages in the cellular synthesis of a protein. I. Movement of mRNA from the nucleus to cytoplasm. II. Linking of adjacent amino acid molecules. III. Transcription of mRNA from a DNA template. IV. Formation of the polypeptide chain. V. Attachment of the mRNA strand to a ribosome. In which order do these stages take place? (a) III I (b) I III (c) I V (d) III IV V II III I II V IV II IV IV II V 216 The difference(s) between mRNA and tRNA is/are that I. mRNA has more elaborated 3-dimensional structure due to extensive base pairing. II. tRNA has more elaborated 3-dimensional structure due to extensive pairing. III. tRNA is usually smaller than mRNA. IV. mRNA contains anticodons, but tRNA contains codons. Choose the correct statements. (a) I, II, III and IV (c) I and III (b) II and III (d) I, II and III 217 Few steps involved in polypeptide synthesis are given below. In which of the following steps does tRNA participates? I. Activation of amino acids by binding with aminoacyl tRNA synthetase enzyme. II. Elongation of polypeptide chain. III. Translation of mRNA to form a polypeptide. IV. Transcription of DNA into RNA. (a) I, III and IV (c) I, II and IV (b) II, III and IV (d) I, II and III 218 Select the correct statements out of the four (I-IV) given below about lac operon. I. Glucose or galactose may bind with the repressor and inactivate it. II. In the absence of lactose, the repressor binds with the operator region. III. Tryptophan acts as an inducer for the gene expression. IV. Regulatory gene is the one that produces the repressor molecule. Choose the correct option. (a) II and III (b) I and III (c) II and IV (d) I and II 219 Which of the following statements concerning the regulatory genes (R), associated with the lac operon are incorrect? I. mRNA is transcribed from the R gene whether lactose is present or not. II. mRNA is transcribed from the R gene only when the lactose is present. III. mRNA is transcribed from the R gene only when the lactose is not present. IV. Lactose inhibits the translation of R gene mRNA. (a) I and II (c) III and IV (b) II and III (d) II, III and IV www.mediit.in 147 CHAPTER 06 > Molecular Basis of Inheritance 220 Identify the incorrect statement for lac operon model. (a) Lactose acts as inducer which inactivates repressor (b) RNA polymerase stay away from promoter in the presence of repressor (c) Regulation of lac operon by repressor is referred to as negative regulation (d) The repressor of the operon is synthesised during specific periods from r-gene 221 Select the incorrect statement from the following. AIIMS 2019 (a) The human genome contains 3164.7 million nucleotide bases (b) Less than 10% of the genome codes for proteins (c) Repeated sequences make up very large portion of the human genome (d) Chromosome 1 has most genes (2968) and Y has the fewest (231) 222 Consider the following statements. I. Major countries who contributed or participated in human genome project were Japan, France, Germany and China. II. Human genome project was a mega project of 13 years. Choose the correct option. (a) Statement I is true, but II is false (b) Statement II is true, but I is false (c) Both statement I and II are correct (d) Both statement I and II are incorrect 225 Tandem Repeat DNA I. is classified as microsatellites and minisatellites. II. normally does not code for any protein. III. shows polymorphism. IV. is used in fingerprinting. Choose the correct option to complete the statement. (a) I and III (c) I, III and IV III. Matching Type Questions 226 Match the following columns. Column I (Scientists) 1. DNA double helix B. Griffith 2. Nuclein C. Hershey and Chase 3. Streptococcus pneumoniae D. Watson and Crick 4. Bacteriophage E. 5. X-ray diffraction studies are I. isolation of total DNA. II. cloning in suitable vectors. III. sequence arrangment by computer. IV. formation of physical and genetic maps. V. converting the fragments. VI. using automated sequencer. VII. using restriction endonuclease recognition sites. VIII. completition of human genome sequencing. Choose the correct option in which the above given steps are arranged properly. (a) (b) (c) (d) I, II, III, IV, V, VI, VII, VIII I, V, II, VI, III, VII, IV, VIII I, II, V, VI, III, IV, VIII, VII I, II, V, VI, III, VII, VIII, IV Wilkins and Franklin Codes A (a) 5 (b) 1 (c) 2 (d) 1 B 4 4 3 3 C 3 3 4 4 D 1 2 1 2 E 2 5 5 5 227 Match the following columns. Column I (Features) Project (HGP). 224 Steps in sequencing Human Genome Project (HGP) Column II (Discoveries) A. F Miescher 223 Choose the incorrect statement about Human Genome (a) Commonly used host for cloning in HGP were PAC (Plasmic Artificial Chromosome) and GMO (Genetically Modified Organisms) (b) The alignment of sequences obtained was done by computer based programs (c) The developed sequences were annotated and were assigned to each chromosome (d) The human genome has 22 autosomes, X and Y (b) I, II and III (d) I, II, III and IV Column II (Associated enzymes) A. RNA digesting enzymes 1. Lipase B. Protein digesting enzymes 2. DNase C. DNA digesting enzymes 3. Protease D. Fat digesting enzymes 4. RNase Codes A (a) 3 (c) 4 B 4 3 C 2 2 D 1 1 A (b) 1 (d) 1 B 2 2 C 4 3 D 3 4 228 Match the following columns. Column I (Enzymes) Column II (Functions) A. Topoisomerase 1. Relaxes the DNA from its super-coiled nature. B. DNA gyrase 2. Relieves strain of unwinding by DNA helicase; this is a specific type of topoisomerase. C. DNA ligase 3. Re-anneals the semiconservative strands and joins okazaki fragments of the lagging strand. D. Telomerase 4. Provides a starting point of RNA (or DNA) for DNA polymerase to begin synthesis of the new DNA strand. www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 148 Codes A (a) 1 (c) 2 232 Match the following columns. B 2 4 C 4 3 D 3 1 A (b) 1 (d) 1 B 2 3 C 3 2 D 4 4 229 Match the following columns. Column I Column II A. Splicing 1. Lac operon B. Okazaki fragment 2. Lagging strand C. Jacob and Monod 3. Lactose 4. Removal of introns D. Inducer Codes A (a) 1 (c) 4 B 2 2 C 3 3 D 4 1 A (b) 4 (d) 2 B 2 4 C 1 3 D 3 1 230 Match the given enzymes with their respective function in DNA replication. Column I Column II A. DNA helicase 1. B. DNA polymerase 2. C. DNA clamp 3. D. Single-Strand Binding (SSB) Proteins Codes A (a) 1 (c) 4 B 2 3 C 4 2 4. D 3 1 A protein which prevents DNA polymerase-III form dissociating from the DNA parent strand. Bind to ssDNA and prevent the DNA double helix from re-annealing after DNA helicase unwinds it thus maintaining the strand separation. Also known as helix destabilising enzyme and unwinds the DNA double helix at the replication fork. Build a new duplex DNA strand by adding nucleotides in the 5′ to 3′ direction. Also performs proofreading and error correction. A (b) 3 (d) 1 B 4 2 C 1 3 D 2 4 231 Match the following columns. Column I Column II A. Sigma factor 1. 5′−3′ B. Capping 2. Initiation C. Tailing 3. 5′ end D. Coding strand 4. 3′ end Codes A (a) 4 (c) 1 B 1 3 C 2 4 D 3 2 A (b) 2 (d) 3 B 4 2 Column I Column II A. tRNA 1. Linking of amino acids B. mRNA 2. Transfer of genetic information C. rRNA 3. Nucleolar organising region D. Peptidyl transferase 4. Transfer of amino acid from cytoplasm to ribosome Codes A (a) 4 (b) 1 (c) 1 (d) 1 B 2 4 2 3 C 3 3 3 2 D 1 2 4 4 233 Match the following columns. Column I Column II A. Exon 1. Coding sequence B. Intron 2. Non-coding sequence C. Genetic code 3. Triplet bases on mRNA D. DNA packaging 4. Nucleosome Codes A (a) 1 (c) 1 B 3 2 C 2 3 D 4 4 A (b) 1 (d) 4 B 4 1 C 2 2 D 3 3 234 Match the following columns. Column I Column II A. 5′–AUG–3′ 1. Segment of DNA B. RNA with introns and exon 2. Chromatin C. Gene 3. hnRNA D. Nucleosomes 4. Initiation codon Codes A (a) 4 (c) 2 B 3 1 C 1 4 D 2 3 A (b) 4 (d) 2 B 2 3 C 1 1 D 3 4 235 Match the following columns. Column I (Functions) C 3 1 D 1 4 Column II (Segments of DNA) A. Segment of DNA coding for polypeptide 1. Recon B. Segment of DNA goes for recombination 2. Muton C. Segment of DNA goes for mutation 3. Cistron www.mediit.in 149 CHAPTER 06 > Molecular Basis of Inheritance Codes A (a) 1 (c) 3 B 2 1 C 3 2 A (b) 3 (d) 1 B 2 3 C 1 2 236 Match the following RNA polymerases with their transcribed products. NEET (Odisha) 2019 A. RNA polymerase-I 1. t RNA B. RNA polymerase-II 2. rRNA C. RNA polymerase-III 3. hnRNA Codes A (a) 1 (c) 2 B 3 3 C 2 1 A (b) 1 (d) 3 B 2 2 C 3 1 their respective products. NEET 2019 Column II i gene 1. β-galactosidase B. z gene 2. Permease C. a gene 3. Repressor D. y gene 4. Transacetylase A. Codes A (a) 1 (c) 3 C 3 1 1 2 D 4 2 4 1 Column I 237 Match the following genes of the lac operon with Column I B 2 4 2 1 239 Match the following columns. Column II Column I Codes A (a) 1 (b) 3 (c) 3 (d) 4 Column II A. Termination (Translation) 1. Aminoacyl tRNA synthatase B. Translation 2. Okazaki fragments C. Transcription 3. D. DNA replication 4. RNA polymerase Codes A (a) 3 (b) 2 (c) 4 (d) 2 B 1 3 3 1 C 4 1 1 3 D 2 4 2 4 240 Identify the correct match between the codons and coding functions. Column I B 2 4 C 3 1 D 4 2 A (b) 3 (d) 1 B 1 3 C 4 2 D 2 4 238 Match the following columns. Column I (Enzymes) Column II (Functions) A. β-galactosidase 1. Joining of DNA fragments B. Permease 2. Peptide bond formation GTP dependent release factor C. Ligase 3. Hydrolysis of lactose D. Ribozyme 4. Increase permeability to β-lactose Column II A. AUG 1. Phenylalanine B. UAA 2. Methionine C. UUU 3. Tryptophan D. UGG 4. Termination Codes A (a) 1 (b) 2 (c) 4 (d) 4 B 4 4 3 1 C 2 1 2 3 D 3 3 1 2 www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 150 NCERT Exemplar MULTIPLE CHOICE QUESTIONS 241 In a DNA strand the nucleotides are linked together by (a) glycosidic bonds (c) peptide bonds (b) phosphodiester bonds (d) hydrogen bonds 242 A nucleoside differs from a nucleotide. It lacks the (a) base (c) phosphate group (b) sugar (d) hydroxyl group 243 Both deoxyribose and ribose belong to a class of sugars called (a) trioses (c) pentoses 244 The fact that a purine always paired base through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix (a) the antiparallel nature (b) the semiconservative nature (c) uniform width throughout DNA (d) uniform length in all DNA 245 Which of the following are the functions of RNA? (a) It is carrier of genetic information from DNA to ribosomes synthesising polypeptides (b) It carries amino acids to ribosomes (c) It is a constituent component of ribosomes (d) All of the above 246 Who amongst the following scientists had no contribution in the development of the double helix model for the structure of DNA? (b) Maurice Wilkins (d) Meselson and Stahl 247 While analysing the DNA of an organism a total number of 5386 nucleotides were found out of which the proportion of different bases were Adenine = 29%, Guanine = 17%, Cytosine = 32%, Thymine = 17%. Considering the Chargaff’s rule it can be concluded that (a) it is a double-stranded circular DNA (b) it is single-stranded DNA (c) it is a double-stranded linear DNA (d) No conclusion can be drawn 248 In some viruses, DNA is synthesised by using RNA as template. Such a DNA is called (a) A-DNA (a) protein (c) DNA (b) B-DNA (c) cDNA (d) rDNA 249 The net electric charge on DNA and histones is (a) positive (b) negative (c) negative and positive, respectively (d) zero (b) carbohydrates (d) RNA 251 If Meselson and Stahl’s experiment is continued for four generations in bacteria, the ratio of 15 N / 15 N : 15 N / 14 N : 14 N / 14 N containing DNA in the fourth generation would be (a) 1:1:0 (b) hexoses (d) polysaccharides (a) Rosalind Franklin (c) Erwin Chargaff 250 The first genetic material could be (b) 1:4:0 (c) 0:1:3 (d) 0:1:7 252 DNA is a polymer of nucleotides which are linked to each other by 3′–5′ phosphodiester bond. To prevent polymerisation of nucleotides, which of the following modifications would you choose? (a) Replace purine with pyrimidines (b) Remove/Replace 3′ OH group in deoxyribose (c) Remove/Replace 2′ OH group with some other group in deoxyribose (d) Both (b) and (c) 253 Discontinuous synthesis of DNA occurs in one strand, because (a) DNA molecule being synthesised is very long (b) DNA-dependent DNA polymerase catalyses polymerisation only in one direction (5′ → 3′) (c) it is a more efficient process (d) DNA ligase has to have a role 254 If the sequence of nitrogen bases of the coding strand of DNA in a transcription unit is 5' – A T G A A T G – 3', the sequence of bases in its RNA transcript would be (a) 5′ – A U G A A U G – 3′ (b) 5′ – U A C U U A C – 3′ (c) 5′ – C A U U C A U – 3′ (d) 5′ – G U A A G U A – 3′ 255 The promoter site and the terminator site for transcription are located at (a) 3′ (downstream) end and 5′ (upstream) end, respectively of the transcription unit (b) 5′ (upstream) end and 3′ (downstream) end, respectively of the transcription unit (c) the 5′ (upstream) end (d) the 3′ (downstream) end 256 The RNA polymerase holoenzyme transcribes (a) the promoter, structural gene and the terminator region (b) the promoter and the terminator region (c) the structural gene and the terminator regions (d) the structural gene only 257 Which one of the following steps in transcription is catalysed by RNA polymerase? (a) Initiation (c) Termination (b) Elongation (d) All of these www.mediit.in 151 CHAPTER 06 > Molecular Basis of Inheritance 258 Which one of the following is true with respect to AUG? (a) lactose is present and it binds to the repressor (b) repressor binds to operator (c) RNA polymerase binds to the operator (d) lactose is present and it binds to RNA polymerase (a) exons and introns do not appear in the mature RNA (b) exons appear, but introns do not appear in the mature RNA (c) introns appear, but exons do not appear in the mature RNA (d) Both exons and introns appear in the mature RNA 265 Regulatory proteins are the accessory proteins that interact with RNA polymerase and affect its role in transcription. Which of the following statements is correct about regulatory protein? (a) They only increase expression (b) They only decrease expression (c) They interact with RNA polymerase, but do not affect the expression (d) They can act both as activators and as repressors 260 To initiate translation, the mRNA first binds to (a) the smaller ribosomal subunit (b) the larger ribosomal subunit (c) the whole ribosome (d) No such specificity exists 266 Which was the last human chromosome to be 261 If the base sequence of a codon in mRNA is 5'–AUG–3', the sequence of tRNA pairing with it must be completely sequenced? (a) Chromosome 1 (c) Chromosome 21 (b) 5′ – CAU – 3′ (d) 5′ – GUA – 3′ (b) Chromosome 11 (d) Chromosome-X 267 The human chromosome with the highest and least 262 The amino acid attaches to the tRNA at its (a) 5′-end (c) Anticodon site (b) transcription (d) None of these 264 In E. coli, the lac operon gets switched on when 259 With regard to mature mRNA in eukaryotes (a) 5′ – UAC – 3′ (c) 5′ – AUG – 3′ 263 Control of gene expression takes place at the level of (a) DNA-replication (c) translation (a) It codes for methionine only (b) It is also an initiation codon (c) It codes for methionine in both prokaryotes and eukaryotes (d) All of the above number of genes in them are respectively (b) 3′-end (d) DHU loop (a) chromosome 21 and Y (b) chromosome 1 and X (c) chromosome 1 and Y (d) chromosome X and Y Answers > Mastering NCERT with MCQs 1 (a) 16 (c) 31 (a) 46 (b) 61 (b) 76 (c) 91 (c) 106 (a) 121 (c) 136 (a) 151 (a) 166 (a) 181 (a) 2 (b) 17 (c) 32 (a) 47 (a) 62 (b) 77 (a) 92 (a) 107 (c) 122 (c) 137 (c) 152 (a) 167 (a) 182 (c) 3 (d) 18 (d) 33 (c) 48 (b) 63 (a) 78 (c) 93 (d) 108 (a) 123 (c) 138 (d) 153 (c) 168 (c) 183 (a) 4 (a) 19 (c) 34 (d) 49 (a) 64 (c) 79 (a) 94 (c) 109 (b) 124 (c) 139 (c) 154 (b) 169 (a) 184 (a) 5 (c) 20 (c) 35 (c) 50 (d) 65 (b) 80 (b) 95 (c) 110 (b) 125 (a) 140 (b) 155 (a) 170 (d) 6 (a) 21 (c) 36 (b) 51 (d) 66 (a) 81 (b) 96 (b) 111 (c) 126 (a) 141 (c) 156 (a) 171 (d) 7 (a) 22 (c) 37 (c) 52 (b) 67 (c) 82 (c) 97 (a) 112 (d) 127 (c) 142 (d) 157 (a) 172 (c) 8 (a) 23 (c) 38 (a) 53 (c) 68 (d) 83 (d) 98 (c) 113 (d) 128 (c) 143 (b) 158 (d) 173 (d) 9 (b) 24 (a) 39 (a) 54 (a) 69 (b) 84 (a) 99 (d) 114 (b) 129 (a) 144 (a) 159 (d) 174 (d) 10 (b) 25 (c) 40 (a) 55 (c) 70 (a) 85 (a) 100 (d) 115 (a) 130 (b) 145 (c) 160 (d) 175 (a) 11 (a) 26 (a) 41 (b) 56 (a) 71 (a) 86 (a) 101 (b) 116 (a) 131 (a) 146 (b) 161 (c) 176 (b) 12 (c) 27 (d) 42 (d) 57 (b) 72 (d) 87 (b) 102 (b) 117 (c) 132 (c) 147 (b) 162 (d) 177 (a) 13 (d) 28 (a) 43 (d) 58 (a) 73 (a) 88 (*) 103 (a) 118 (c) 133 (d) 148 (d) 163 (b) 178 (b) 14 (d) 29 (b) 44 (c) 59 (c) 74 (b) 89 (c) 104 (b) 119 (a) 134 (c) 149 (b) 164 (c) 179 (c) 15 (b) 30 (c) 45 (b) 60 (a) 75 (a) 90 (c) 105 (c) 120 (a) 135 (c) 150 (b) 165 (d) 180 (b) 190 (a) 205 (c) 220 (d) 235 (c) 191 (a) 206 (d) 221 (b) 236 (c) 192 (a) 207 (c) 222 (c) 237 (b) 193 (a) 208 (d) 223 (a) 238 (b) 194 (b) 209 (d) 224 (b) 239 (a) 195 (a) 196 (b) 197 (a) 198 (b) 199 (a) 210 (a) 211 (d) 212 (c) 213 (d) 214 (d) 225 (d) 226 (c) 227 (c) 228 (b) 229 (b) 240 (b) 245 (d) 246 (d) 247 (b) 248 (c) 249 (c) 250 (d) 251 (d) 252 (b) 253 (b) 254 (a) 255 (b) > NEET Special Types Questions 185 (d) 200 (b) 215 (a) 230 (b) > 186 (a) 201 (c) 216 (b) 231 (b) 187 (a) 202 (c) 217 (d) 232 (a) 188 (a) 203 (d) 218 (c) 233 (c) 189 (a) 204 (d) 219 (d) 234 (a) NCERT Exemplar Questions 241 (b) 242 (c) 256 (c) 243 (c) 244 (c) 257 (b) 258 (d) 259 (b) 260 (a) 261 (b) 262 (b) 263 (b,c) 264 (a) 265 (d) 266 (a) 267 (c) www.mediit.in 152 Master The NCERT > BIOLOGY (Vol-II) Answers & Explanations 1 (a) DNA is a long chain of polymer of 2 3 4 7 10 13 16 deoxyribonucleotide in which a phosphate group is attached to 5′− OH of nucleoside through phosphodiester linkage. (b) Length of DNA is directly proportional to the number of nucleotides. As the number of nucleotides increases, the length of DNA also increases. (d) Option (d) is the incorrect match and can be corrected as Haploid content of human DNA is 3.3 × 109 bp. Rest of the matches are correct. (a) Adenine and guanine are the purines which are found both in DNA and RNA. Cytosine and thymine are the pyrimidines which are found in DNA. In case of RNA, thymine is replaced by uracil. (a) Adenosine and deoxyadenosine differ in only sugar. Nitrogenous bases are attached to the pentose sugar by N-glycoside bond. If ribose sugar is present then it is called nucleoside and when deoxyribose sugar is present then it is called deoxynucleoside, i.e. adenoside (sugar is ribose), deoxyadenoside (sugar is deoxyribose), cytidine, deoxycytidine, uridine or deoxythymine. (b) Adenylic acid, cytidilic acid and guanylic acid are nucleotides. A nucleotide is composed of three components – nitrogen base (adenosine, cytosine, guanine), ribose sugar and a phosphate group. These are monomer unit of nucleic acid, i.e. RNA and DNA. Adenine, cytidine, thymidine are nucleosides. Uracil, cytosine and adenosine are nitrogenous bases. (d) Thymine and uracil, both have similar structures and are pyrimidine. Thymine ring has one additional methyl group at 5′ position in its pyrimidine ring. Therefore it is also called 5 methyl uracil. (c) The percentage of bases which are pyrimidines is 50%. According to Chargaff’s rule A + G = C + T = 50% (Purines) Answers & Explanations ∴ (Pyramidines) If A = 20%, then T = 20% C + T = 50% C = 50% − 20% = 30% Total percentage of pyrimidine bases (T + C) are 20 + 30 = 50% 17 (c) Chargaff’s rule states that purine and pyrimidine base pairs are present in equal amount in dsDNA, i.e. A = T, G = C. i.e. ( A + T ) = ( G + C ) A+T =1 ∴ G+ C If cytosine = 17%, then G = 17% If A + G + C + T = 100 and G = C, A = T A + 17 + 17 + T = 100 A + T + 34 = 100 A + T = 100 − 34 A + T = 66 A = T = 66 / 2 = 33% Hence, if cytosine is 17% then G = 17% and A and T will be 33% each. 20 (c) Option (c) is incorrect and can be corrected as Adenine forms two hydrogen bonds with thymine of the opposite strand and vice-versa. On the other hand, guanine is bounded with cytosine with three H-bonds. Rest of the options are correct. 23 (c) The length of DNA in a human cell is about 2.2 m. It can be calculated as The distance between two consecutive base pairs = 0.34 nm or 0.34 × 10−9 m then If the length of DNA double helix in a typical mammalian cell = The total number of bp × Distance between two consecutive bp = 6.6 × 109 bp × 0.34 × 10−9 m/bp = 2.2 m 24 (a) In the given case, the number of base pairs for E. coli would be 4 × 106 bp. It can be calculated as Average distance between two base pairs of DNA is 3.4 Å. Length of E. coli DNA is = 1.36 × 107 Å 1.36 × 107 Å = 0.39 × 107 So, number of nucleotides = 3.4Å ~ 4 × 106 bp = 3.9 × 106 = 26 (a) In a eukaryotic cell, the DNA packaging has positively charged basic proteins called as histones. A protein acquires charge depending upon the abundance of amino acids residues with charged side chains. Histones are rich in basic amino acid residues lysine and arginine and hence are positively charged. 27 (d) Option (d) is the incorrect match and can be corrected as Chromatin are thread-like stained (coloured) bodies seen in nucleus. The nucleosomes in chromatin are seen as ‘beads on string’ when viewed under electron microscope. Rest of the matches are correct. 28 (a) Linker-DNA is attached to H1 histone protein. Linker DNA connects two adjacent nucleosomes. Its length is varied (about 145 Å with 70 bp). Nucleosome and linker DNA together constitute chromatosome. Chromatosome contains a histone octamer and DNA. 29 (b) The packaging of chromatin at higher level requires an additional set of proteins that are collectively called non-histone proteins (i.e. H2A and H2B). www.mediit.in 153 CHAPTER 06 > Molecular Basis of Inheritance 30 (c) The association of H1 histone with nucleosome 35 37 38 58 60 62 63 65 67 44 (c) Option (c) is the incorrect trait and can be 47 49 50 55 56 corrected as A molecule that can act as a genetic material must be stable structurally and chemically. Rest of the options are correct. (a) Both DNA and RNA are able to mutate. Infact RNA being unstable, mutates at a faster rate. Consequently, viruses having RNA genome and shorter lifespan, mutate and evolve faster. (a) RNA was the first genetic material. There is now enough evidence to suggest that the essential life processes has evolved around RNA. (d) Chargaff’s rule is not applicable to RNA. It is the generalised formula about DNA structure. The rule states that DNA from any cell of an organism should have a 1 : 1 ratio (base pair rule) of pyrimidine and purine bases, i.e. the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. (c) Heavy DNA molecule could be distinguished from the normal DNA by centrifugation in a cesium chloride (CsCl) density gradient. (a) In Meselson and Stahl’s experiment, the generation time (replication time) of E. coli culture is about 68 20 minutes. Therefore, the DNA extracted after the interval of 20 minutes in the experiment had heavy 15 N incorporated in its genetic material and had a hybrid density. (a) An experiment similar to Meselson and Stahl experiment was performed on Vicia faba (faba beans) by Taylor and colleagues in 1958. The experiments proved that the DNA in chromosomes also replicate semiconservatively. (a) DNA polymerase is DNA dependent because it uses DNA template to catalyse the polymerisation of deoxynucleotides. (b) Separation of the entire length of DNA helix needs a large amount of energy. Hence, only up to certain extent separation of DNA helix can take place. (a) Replication fork is a Y-shaped structure formed due to small opening of DNA helix for replication to take place. This is formed because long DNA molecules cannot be separated along the entire length (due to very high energy requirement). (b) The replication is continuous on 3′ → 5′ polarity strand because DNA polymerase can catalyse polymerisation in 5′ → 3′ direction only and we know that DNA strands are complementary to each other. Thus, continuous synthesis occurs in 3′ → 5′ direction. (c) During DNA replication, super coiling is relaxed by DNA topoisomerase. These enzymes participate in underwinding of DNA. Other options functions as, l SSBPs are single strand binding proteins which stabilises the unwound parental DNA. l Primase is the enzyme which synthesise RNA primer on DNA template to initiate DNA synthesis. l RNA polymerase enzyme helps in synthesis of new DNA strand during replication. (d) Okazaki fragments are short segments of replicating DNA. These have 1000-2000 bp in prokaryotes and 100-200 bp in eukaryotes. These fragments are formed discontinuously and are used to elongate the lagging strand away from the replication fork. 69 (b) Option (b) is correct. The phosphorylated nucleotides are deATP (deoxy Adenosine Triphosphate), deCTP (deoxy Cytidine Triphosphate), deTTP (deoxy Thymidine Triphosphate). These triphosphates serve dual purpose. These act as substrate as well as provide energy for polymerisation of nucleotides by releasing energy after dissociating the phosphate group. 70 (a) Option (a) contains the wrongly matched pair and can be corrected as Transcription is a process of RNA synthesis from a DNA template. Rest of the options contain correct pairs. 71 (a) The strands in the DNA are complementary to each other, not identical. If the two RNAs are formed from both strands then RNAs with different sequences would be formed. Answers & Explanations 34 indicates that DNA is condensed into chromatin fibre. In eukaryotes, DNA packaging is carried out with the help of histone proteins. Nucleosome is the unit of compaction. Its core consists of four pairs of histones (H2A, H2B, H3 and H4). The linker DNA, consisting of H1 histone connects two adjacent nucleosomes. These together constitute chromatosome. It gives rise to a chromatin fibre after further condensation. (d) Frederick Griffith (1920) conducted a series of experiments on the bacterium Streptococcus pneumoniae. Through his experiment he found out that the heat-killed S-strain bacteria had changed the R-strain to virulent form. He called this the transforming principle. (c) In Griffith’s experiment, he found out that something from dead organism could change the living cells. From his experiment he showed that dead S-bacteria (virulent) are changing (transforming) the R-bacteria (non-virulant) into S-type, i.e. the virulent strain. (c) Alfred Hershey and Martha Chase (1952) experimentally proved that DNA is the sole genetic material in bacteriophage. On the other hand, Beadle and Tatum (1940s) experimentally showed one gene-one enzyme hypothesis using Neurospora. Meselson and Stahl first showed that DNA replicates semiconservatively through experiments on E. coli. Jacob and Monod were first to explain lac operon. (a) Hershey and Chase grew cultures of Escherichia coli. One culture was supplied with radioactive sulpur ( 35 S) and the another with radioactive phosphorus ( 32 P). www.mediit.in 154 Master The NCERT > BIOLOGY (Vol-II) structures are not a part of RNA polymerase. Thus, RNA polymerase can perfom the function of elongation only. 72 (d) Option (d) is correct. 73 75 78 79 80 81 Answers & Explanations 82 84 85 87 If both strands are copied during transcription, then two complementary RNA strands will be produced simultaneously. These would have the tendency to form double-stranded RNA and if these two RNA strands do not form double helix these would code for two different types of proteins. Then, the whole exercise of transcription would be futile. (a) If double-stranded RNA is produced during transcription this would prevent RNA from being translated into proteins. Double-stranded RNA have more stability than single-stranded RNA. If double-stranded RNA is formed from transcription, then it is difficult to separate the strands of RNA due to which translation would be halted. (a) The strand, which does not code for anything is referred to as coding strand. All the reference point, while defining a trancription unit is made with the coding strand. (c) Coding strand is the one that codes for mRNA. It has same nucleotide sequence as that of mRNA except thymine (T) is replaced by uracil (U) in mRNA. Hence, the corresponding sequence of transcribed mRNA by template or non-coding strand (complementary to RNA) is AGGUAUCGCAU. (a) Among the given options, only the mRNA given in option (a) can be transcripted because it possesses an initiation codon-AUG which codes for methionine. Rest of the mRNA sequences start with termination codons, i.e. UAA (Ochre), UAG (Amber) and UGA (Opal). Therefore, these cannot be transcripted. (b) Option (b) gives the sequence of mRNA produced by the given stretch of DNA. The mRNA will be complementary to the DNA strand, but in RNA, uracil will be present in place of thymine. If the template strand is 3′–ATGCATGCATGCATG–5 then the base sequence of mRNA for the given DNA strand will be 5′–UACGUACGUACGUAC–3’. (b) Promoter is present at the 5′-site of structural gene and terminator is present at the 3′-site of structural genes. Thus, we can say that promoter and terminator flanks the structural genes. (c) Option (c) is incorrect and can be corrected as Cistron is a segment of DNA coding for a polypeptide. Rest of the options are correct. (a) rRNA is the most abundant form of RNA; because it is responsible for coding and protein synthesis in the cell and is also associated with ribosomes. (a) DNA-dependent RNA polymerase catalyses transcription on one strand of the DNA called as template strand. A template can be considered as one of those strands of DNA which decodes its information directly through RNA polymerase. (b) RNA polymerase only catalyses the elongation process of transcription. The initiation of transcription is done by sigma (σ) unit. The termination of the transcription is acheived by rho (ρ) factor. These two 88 (*) This question is incorrect because out of the given initiation and termination factors, none is involved in transcription in eukaryotes. However, option (a) contains initiation and termination factors which are involved in transcription. These factors (σ and ρ) initiate and terminate transcription in prokaryotes (not in eukaryotes). Initiation and termination factors involved in transcription in eukaryotes are General Transcription Factors (TF IIA TF II H) and Transcription Termination Factor-1 (TTF-1), respectively. 90 (c) Option (c) is correct. In prokaryotes, mRNA does not require any processing to become active and there is no clear demarcation between the nucleus and cytoplasm. Genetic material is dispersed through out the cytoplasm. Thus, transcription and translation takes place in the same compartment in prokaryotes. 91 (c) In the process of transcription (i.e. copying of 92 93 95 97 genetic information from one strand of the DNA into RNA) in eukaryotes, the enzyme RNA polymerase-I transcribes rRNA - 28S, 18S and 5.8S. On the other hand, tRNA, 5srRNA and snRNAs are transcribed by RNA polymerase III. RNA polymerase-II transcribes precursor of mRNA, i.e. hnRNA. (a) RNA undergoes a process where the introns (non-coding parts) are removed and exons (coding sequence) are joined to form mRNA. This process is called splicing. (d) Spliceosome is absent in cells of bacteria. It is a large molecular complex found in nucleus of eukaryotic cells of plants, animals and fungi. It is assembled from snRNAs and protein complexes which play an important role in splicing of introns. (c) At the 5′ end of eukaryotic mRNA, 7 mG (7-methyl guanosine) is present. In eukaryotes, primary transcript is often larger than the functional RNAs. Therefore, post-transcription processing is required to convert primary transcript of all types of RNAs into functional RNAs. It is of four types; cleavage, splicing, terminal addition and nucleotide modification. The terminal additions include capping and tailing. In capping, 7 mG is added to 5′ end of mRNA. (a) Fully processed hnRNA to undergo translation is called mRNA. hn (heterogenous nuclear) RNA is the raw form of mRNA containing both introns and exons. After splicing and post-transcriptional modification of hnRNA, mRNA is formed. 104 (b) Polynucleotide phosphorylase enzyme is used in polymerising RNA with defined sequences in a template independent manner (enzymatic synthesis of RNA). It is also called Servo Ochoa enzyme. www.mediit.in 155 CHAPTER 06 > Molecular Basis of Inheritance 109 113 114 115 117 118 119 121 123 64 codons. The rest three are non-sense codons which are used for stopping translation. These are also called stop codons. (b) UAC is not a stop codon. It codes for tyrosine amino acid. The last codon of a functional gene which helps in termination of the polypeptide chain, is termed as stop or termination codon. These are UAA, UAG and UGA. These codons do not have tRNA to be translated. (d) Degeneracy refers to the fact that one amino acid has more than one code triplet and the codons which specify the same amino acids differ only in the third base of the triplet, e.g. both CAC and CAU code for the amino acid histidine. (b) Bacteria is able to produce human insulin because genetic code is nearly universal in all organisms. For example, the codon AGG specifies amino acid arginine in bacteria, animals and plants. But there are also some exceptions, e.g. in mitochondria, the stop codon UGA for humans specifies amino acid tryptophan. (a) Mutation gives rise to alterations in the phenotype. This is the reason as to why mutation is best for studying the relationship between genes and DNA for their expression. (c) The reading frame of given mRNA will not change even after the deletion of GGU from 7th, 8th and 9th positions. However, only the amino acid glycine will not be formed at third position in this case which is being coded by GGU. In rest of the cases, insertion or deletion of one or two nucleotide bases would result in the complete alteration in the reading frame of mRNA. (c) 33 codons will be altered if the base at position 901 is deleted from an mRNA having 999 bases. This can be calculated as Total number of bases in the given mRNA = 999 999 Number of codons for this mRNA = = 333 3 If one base is deleted at position 901 then the number 900 bases unchanged are 900 which codes for 3 = 300amino acids Thus, number of altered codons will be 333 − 300 = 33 (a) Frameshift mutation of the genetic bases (deletion or addition) gives the proof that codon is triplet and reads in contagious manner. Deletion or addition of a base pair disturb the reading frame of DNA or mRNA. (c) tRNA was known as sRNA (soluble RNA) before the genetic code was postulated. Its role as an adaptor molecule was reported later. (c) Option (c) is incorrect and can be corrected as tRNA are specific for each amino acid, e.g. for initiation there is a specific initiator tRNA. Rest of the options are correct for tRNA. 124 (c) Three dimensional structure or compact form of 125 126 128 129 130 135 137 138 139 tRNA was given by Klug in 1974. It looks like the letter 'L' of English alphabet. Hence, it is called as the L-form model of tRNA. (a) tRNA binds to mRNA through anticodon loop, as it bears bases complementary to those on mRNA being translated. The amino acid loop of tRNA is involved in binding the respective amino acid. The T ψ C loop helps in binding the amino acid, while the D-loop of tRNA is the binding site for aminoacyl synthetase. (a) RNA polymerase-III transcribes the synthesis of tRNA, therefore tRNA synthesis will be affected if it is removed from nucleoplasm. RNA polymerase-II synthesises mRNA while, RNA polymerase-I synthesis rRNA in eukaryotes. (c) Polysome is a string of ribosomes associated with a single mRNA. Polysome helps to produce a number of copies of the same polypeptide. (a) In the process of protein synthesis, tRNA carrying the amino acids enters the A-site of the ribosome. Peptide bonds that are formed between the amino acids are present on P and A-site. (b) According to the sequences present on the mRNA, amino acids are produced. Thus, the order and the sequence of the amino acids are defined by mRNA. (c) UTRs present on mRNA refer to Untranslated Regions present at both 5′–end (before start codon) and 3′–end (after stop codon). These are the additional sequences that are not translated. These are required for efficient translation process. (c) Option (c) contains the incorrect match and can be corrected as A translational unit in mRNA is the sequence of RNA that is flanked by the start codon (AUG) and ends at the stop codon and codes for a polypeptide. Rest of the matches are correct. (d) Option (d) represents the correct sequential code of tRNA. DNA and mRNA have complementary base pairs. If the DNA is 3′–TAC ATG GGT CCG–5′ than mRNA will have II I IV III 5′–AUG UAC CCA GGC–3′ tRNA and mRNA have complementary base pairs. (c) Option (c) is correct as UAA, UAG and UGA are stop codons on mRNA for which no tRNA molecules are present. tRNA molecules have anticodon, therefore anticodons for the mentioned stop codons will AUU, AUC and ACU which does not exist. 144 (a) Positively regulatory proteins are called activators. These activator proteins bind to regulatory sites on DNA near to the promoter regions which act as on / off switches. This binding facilitates RNA polymerase activity and transcription of nearby genes. Answers & Explanations 105 (c) 61 codons code for amino acids out of the total www.mediit.in 156 Master The NCERT > BIOLOGY (Vol-II) 145 (c) In the operon system, the promoter is generally situated beside the operator genes. In the prokaryotes, the working of promoter region (binding of RNA polymerase) is coordinated by the operator genes, e.g. if operator genes are occupied by the repressor proteins then RNA polymerase does not bind to the promoter gene and there is no transcription. 157 (a) An inducer binds with the repressor protein and 160 146 (b) An operon is considered to regulate genetic unit or DNA. It act as a single regulatory unit having one or more structural genes, an operator gene, regulator genes, a repressor and an inducer. 148 (d) Option (d) is the correct match. Jacob and Monod (1916) discovered the lac operon. Rest of the matches are incorrect and can be corrected as l Matthew Meselson and F Stahl discovered the semiconservative mode of DNA replication in E. coli. l Alfred Hershey and Martha Chase use T2 bacteriophage in their experiments to infect E. coli and proved that DNA is the genetic material. l Alec Jeffreys (1984) invented the DNA fingerprinting technique. This technique determines nucleotide sequences of certain areas of DNA which are unique to each individual. 161 163 164 149 (b) A lac operon has one regulatory gene (i.e. i-gene) 150 Answers & Explanations 151 153 156 and three structural genes (i.e. z, y and a genes). (b) Gene regulation governing lactose operon of E. coli that involves the Lac i gene products is negative and inducible because its repressor protein prevents transcription. Lac i gene produces an inhibitor or repressor that induces negative regulation of lac operon. The repressor binds to the operator gene and stops its working. Repressor is meant to block the operator gene, so that structural genes are unable to form mRNA, thus stopping the transcription of genes. On the other hand, lactose operon is inducible operon system. It is a regulated unit of genetic material which is switched on in response to the presence of a chemical. (a) β-galactosidase enzyme will be produced in a cell in which non-sense mutation takes place in the lac y gene. Non-sense mutation stops polypeptide synthesis due to the formation of non-sense codon. In lac operon, sequence of structural genes is z (codes for β-galactosidase), y (permease) and a gene (transacetylase). Due to non-sense mutation at y-gene, permease synthesis will be stopped resulting in non-expression of both y and successive gene a also. Thus, only β-galactosidase enzyme will be produced. (c) Lactose is the substrate for the enzyme beta (β) galactosidase and it regulates the switching on and off of the lac operon. Hence, it is termed as inducer. (a) Repressor protein attaches to the operator gene. It is a regulatory protein synthesised by regulator gene. Repressor is meant for blocking the operator gene, so that the structural genes are unable to form mRNA. 165 166 170 171 172 prevents the repressor protein from binding to the operator. Glucose and galactose cannot act as an inducer because these do not have the binding sites for attaching the repressor protein. (d) Option (d) is incorrect and can be corrected as During human genome project many non-human organisms such as bacteria, yeast, C. elegans, Drosophila, plants, etc. DNA were also sequenced. Rest of the options are correct. (c) Gene or DNA library is a collection cloned or copied DNA (cDNA) of cells or tissues, organs of an organism in a preserved form for future use. (b) Option (b) is the incorrect match and can be corrected as Sequence annotation is simply sequencing the whole set of genome that contained all the coding and non-coding sequence and later assigning different regions in the sequence with functions. Rest of the matches are correct. (c) For generating genetic and physical maps, restriction endonuclease was used. For sequencing the human DNA, the entire DNA from a cell is isolated and converted into random fragments of relatively smaller size by using restriction endonuclease enzyme and cloned in suitable host using specialised vectors. (d) Chromosome number 21, 22 and Y are listed in G group. To make chromosomal studies easier, chromosomes are classified into Groups A to G as given below. Group A contains 1-3 chromosomes B contains 4-5 chromosomes C contains 6-12 chromosomes and X-chromosome D contains 13-15 chromosomes E contains 16-18 chromosomes F contains 19-20 chromosomes G contains 21-22 chromosomes and Y- chromosome (a) Human genome is said to have approximately 3 × 109 bp, but the exact number is 3164.7 million bp. (d) Option (d) is correct as reptitive sequences are stretches of DNA sequences that are repeated many times, (sometimes hundred to thousand times). These are thought to have no direct coding functions, but these shed light on chromosome structure, dynamics and evolution. (d) Option (d) is incorrect and can be corrected as Repetitive DNA sequences are stretches of DNA sequences that are repeated many times, sometimes hundred to thousand times. Rest of the options are correct. (c) There are about 1.4 million locations where single base DNA differences occurs. These locations are called SNPs (snips) or Single Nucleotide Polymorphism in humans. www.mediit.in 176 (b) Sattelite DNA is important because it shows high 182 183 185 186 187 188 189 190 191 degree of polymorphism (variation at genetic level) in population and also the same degree of polymorphism in an individual, which is heritable from parents to children. Also satellite DNA does not code for proteins or enzymes but are different in all the members of a population. (c) PCR (Polymerase Chain Reaction) is the technique in which many copies of DNA can be produced in a short period of time. It can increase the sensitivity of DNA fingerprinting. (a) In Southern blotting DNA is transferred from electrophoresis gel plate to the nitrocellulose or nylon membrane sheet. (d) Assertion is false, but Reason is true. Assertion can be corrected as DNA serves as the genetic material in most organisms, but in some viruses like TMV, RNA acts as the genetic material. DNA is a double-stranded biomolecule, but can also exist as a single-stranded biomolecule. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The two chains of DNA have antiparallel polarity. This is because one chain has a free phosphate moiety at the 5′ end of the ribose sugar and another chain has a free phosphate moiety at the 3′ end. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Adenine cannot pair with cytosine. Adenine pairs with thymine and cytosine pairs with guanine. This occurs because adenine pairs with thymine with two hydrogen bonds, i.e. have only two hydrogen donor / hydrogen acceptor sites whereas cytosine has three hydrogen donor / hydrogen acceptor sites. Thus, due to lack of complementarity between the hydrogen donor and hydrogen acceptor sites between adenine and cytosine, these cannot pair. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Histones are basic in nature because these are rich in amino acids lysine and arginine which are basic in nature. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Heterochromatin is densely packed and inaccessible to transcription factors. Hence, it is rendered transcriptionally silent or inactive. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. RNA is an unstable catalytic molecule. It mutates at a faster rate than DNA. Thus, viruses having RNA genome and shorter lifespan, mutate and evolve faster due to this unstability. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The DNA-dependent DNA polymerase works in the 5′ → 3′ direction requiring a free 3′–OH of a pre-existing polynucleotide for initiating DNA 192 193 194 195 196 197 replication. Thus, it continuously synthesises the strand having polarity 3′ → 5′. Replication of the lagging strand (5′→ 3′) generates small polynucleotide fragments, okazaki fragments. The replication of this strand is discontinuous. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. In eukaryotes, replication and transcription take place in the nucleus. The fully processed hnRNA now called mRNA, is transferred from the nucleus into the cytoplasm, where translation occurs. This is because all the amino acids, tRNA and ribosomes required for translation are present in the cytoplasm. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The primary transcript in eukaryotes, i.e. the hnRNA is much larger as it contains both introns and exons. It is the precussor of mRNA. During post-transcriptional modification. Introns (the intervening sequences), which do not code for proteins are removed and all exons are joined to form fully prossessed mRNA. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Polycistronic mRNA, commonly found in prokaryotes, two or more coding regions are present and can specify a number of polypeptide chains or proteins. It further contains multiple (open) reading frames to enable the formation of two or more proteins. Both polycistronic and monocistronic mRNAs have a 5′ leader sequence, the coding region (containing initiation codon and termination codon) and a non-translated 3′ trailer sequence. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. In transcription, the strand with 3′ → 5′ polarity acts as the template from which mRNA is transcribed as is called the template strand. This is because the enzyme DNA-dependent RNA polymerase catalyses polymerisation in only 5′ → 3′ direction. (b) Both the Assertion and Reason are true, but Reason is not the correct explanation of Assertion. In eukaryotes, transcription, i.e. synthesis of RNA from DNA, occurs inside nucleus, because the genetic material DNA is enclosed within the nucleus in eukaryotes. In prokaryotes like bacteria, the genetic material, DNA remains suspended within the cytoplasm. Thus, in prokaryotes the processes of transcription and translation occur in cytoplasm. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The genetic code is degenerate. It means that a given amino acid can be coded by more than one codon. For example, serine is an amino acid coded by UCU, UCC, UCA, UCG, AGU and AGC. Answers & Explanations 157 CHAPTER 06 > Molecular Basis of Inheritance www.mediit.in 158 Master The NCERT > BIOLOGY (Vol-II) 198 (b) Both Assertion and Reason are true, but Reason is 199 200 201 202 204 Answers & Explanations 205 207 210 not the correct explanation of Assertion. mRNA has some additional sequences that are not translated known as Untranslated Regions (UTR). The UTRs are present at both 5′ end (before start codon) and at 3′ end (after stop codon). These are required for efficient translation process. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. DNA fignerprinting is very well-known for its application in paternity testing as it employs the principle of DNA polymorphism. DNA fingerprinting involves the use of satellite DNA. These sequences do not code for any proteins, but show high degree of polymorphism. These serve as the basis of DNA fingerprinting. These polymorphisms are inheritable from parents to children and thus DNA fingerprinting is the basis of paternity testing. (b) Statements I, II, III and IV are correct. Statement V is incorrect and can be corrected as Ribose sugar can be represented as C5 H10 O5 whereas deoxyribose sugar (has deficit of one oxygen atom) can be represented as C5 H10 O4 . (c) The statement in option (c) is incorrect and can be corrected as Nucleotides do not have proteins, carbohydrates and fats. Nucleotides contain a sugar, a phosphate group and a nitrogenous base. Rest of the statements are correct. (c) Statements I, II and IV are correct. Statement III is incorrect and can be corrected as Transforming principle is associated with genetic material of S-strain. (d) Statements I, II and IV are correct. Statement III is incorrect and can be corrected as 35 S will end up in the supernatant after centrifugation as sulphur is present in proteins. (c) The statement in option (c) is incorrect and can be corrected as Equal amount of heavy DNA and light DNA was observed in E. coli culture after the two generations. Rest of the statements are correct. (c) The statement in option (c) is incorrect and can be corrected as Meselson and Stahl proposed the semiconservative DNA replication scheme. Rest of the statements are correct. (a) The statement in option (a) is correct. Rest of the statements are incorrect and can be corrected as l Exon is the coding or expressed sequence, intron is the non-coding sequence and cistron is the segment of DNA which codes for a polypeptide. The region of DNA where transcription starts is promoter. l The terminator codes for the end of transcription. 212 (c) The statement in option (c) is incorrect and can be corrected as The coding sequences or expressed sequences are called exons. Intervening sequences or non-coding sequences in an unprocessed RNA are called introns. Rest of the statements are correct. 214 (d) Statements II and III are correct. Statements I and IV are incorrect and can be corrected as l rRNA provides the site for protein synthesis. l A segment of DNA coding for polypeptide is called cistron. l 216 (b) Statements II and III are correct. Statements I and IV are incorrect and can be corrected as l mRNA does not have an elaborated 3 D structure, it is a linear chain. l mRNA contains codons and tRNA contains anticodons. 217 (d) Steps in statements I, II and III are related with tRNA as these are steps of polypeptide synthesis, i.e. translation. Steps in statement IV is not related with tRNA. This is because transcription involves copying of genetic information from the template DNA strand to RNA. tRNA does not participates inthis process. 218 (c) Statements II and IV are correct. Statements I and III are incorrect and can be corrected as l Glucose and galactose are formed from allolactose by β-galactosidase. These bind with the lactose repressor and activate it is enable the transcription process. l Tryptophan acts as repressor to stop gene expression. 219 (d) Statement II, III and IV are incorrect and only statement I is correct. This can be explained as in lac operon model, regulatory gene is continuously working, whether lactose (inducer) is present or not. It transcribes mRNA which codes for repressor. When this repressor binds with lactose (inducers) it inhibits translation of operator gene (not R gene). Thus, lactose presence affects operator gene not R gene. 220 (d) The statement in option (d) is incorrect and can be corrected as The repressor of the operon is synthesised (all-the-timeconstitutively) from the i gene. The repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon. Rest of the statements are correct. www.mediit.in 159 CHAPTER 06 > Molecular Basis of Inheritance 223 242 243 244 245 246 247 248 corrected as Less than 2% of the genome codes for proteins. In most of organisms more than 98% of human genome is composed of non-coding DNA (or Junk DNA). Rest of the statements are correct. (a) The statement in option (a) is incorrect and can be corrected as BAC or Bacterial Artificial Chromosome and YAC or Yeast Artificial Chromosome are the two vectors generally used in human genome project for cloning the large fragments of human DNA. Rest of the statements are correct. (c) A nitrogenous base is attached to the pentose sugar by an N-glycosidic linkage to form a nucleoside, i.e. Nucleoside=Nitrogen base + Pentose sugar. When a phosphate group is attached to the 5′-OH of a nucleoside through phosphodiester linkage, a nucleotide is formed, i.e. Nucleotide = Nitrogen base + Pentose sugar + Phosphate (PO4 ). So, a nucleoside differs from a nucleotide as it lacks phosphate group. (c) Both deoxyribose and ribose belong to the class of sugar called pentoses as these sugars contain five carbon atoms. (c) The diameter of the strand is always constant due to the pairing of a purine (adenine and guanine) with a pyrimidine (cytosine and thymine). This specific bonding gives uniform width throughout the DNA. (d) Option (d) is correct. rRNA, mRNA and tRNA are the major classes of RNAs that are involved in gene expression. Their functions include rRNA binds protein molecules and forms a ribosome. mRNA carries coded information for translation and polypeptide formation. tRNA is called soluble or adaptor RNA which carries amino acids to ribosomes during protein synthesis. (d) Meselson and Stahl had no contribution in the development of double helix model. In 1958, Meselson and Stahl performed experiments on E. coli to prove that DNA replication is semiconservative. (b) According to Chargaff’s rule of base pairing A G i.e. = =1 T C For the given organism, the DNA does not follow A 27 32 G Chargaff’s rule as = =/ = =/ 1 T 17 17 C Hence, it can be concluded that it is a single-stranded DNA, not double-stranded. (c) In some viruses, like retroviruses (e.g. HIV), complementary DNA (cDNA) is synthesised by using an RNA template. This process is termed reverse transcription and an enzyme called reverse transcriptase is used. 249 (c) The net electric charge on DNA and histones is negative and positive, respectively. DNA consists of a nitrogenous base, pentose sugar and a phosphate group. DNA has negative charge due 3− to the presence of phosphate group (PO4 ). Histones are rich in basic amino acid residues lysine and arginine, which carry positive charge in their side chains. Therefore, histones are positively charged. 250 (d) The first genetic material could be RNA. We know that RNA is present as a genetic material in some viruses, and it also works as a catalyst (there are some important biochemical reactions in living systems that are catalysed by RNA catalysts and not by protein enzymes). But, RNA being a catalyst is reactive and hence unstable. Therefore, it is considered that DNA has evolved from RNA thereby making RNA the first genetic material. 251 (d) Option (d) is correct. Meselson and Stahl found that DNA of the first generation was hybrid or intermediate (15 N and 14 N). It settled in caesium chloride at a level higher than the fully labelled DNA of parent bacteria (15 N 15N ). The second generation of bacteria after 40 minutes, contained two types of DNA, 50% light ( N14 N14 ) and 50% intermediate ( N15 N14 ). The third generation of bacteria after 60 minutes contained two types of DNA, 25% intermediate ( N15 N14 ) and 75% light ( N14 N14 ) in 1 : 3 ratio. It can be assumed that the fourth generation after 80 minutes would contain 12.5% N15 N14 and 87.5% N14 N14 DNA in 1:7 ratio. Thus, if Meselson and Stahl’s experiment is continued for four generations in bacteria, the ratio of 15 N / 15 N :15 N / 14 N : 14 N / 14 N containing DNA in the fourth generation would be 0 : 1 : 7. 252 (b) To prevent polymerisation of nucleotides, 3′ OH group in deoxyribose should be replaced/removed. This is because DNA polymerase enzyme requires a free 3′–OH end of pre-existing polynucleotide to enable polymerisation, leading to the formation of a continuous strand in the 5′→ 3′ direction. 254 (a) Option (a) gives the correct sequence of bases in the RNA transcript for the given DNA coding strand. 5′ - A T G A A T G - 3′ (coding strand) ↓ 3′- T A C T T A C - 5′ (template strand) ↓ 5′ -A U G A A U G - 3′ (RNA) 255 (b) The promoter is located towards 5′ end (upstream) of the structural gene of coding strand and provides the binding site for RNA polymerase to initiate transcription. The terminator region is where the transcription stops and it is present at the 3′ end (downstream). Answers & Explanations 221 (b) The statement in option (b) is incorrect and can be www.mediit.in 160 Master The NCERT > BIOLOGY (Vol-II) 257 (b) RNA polymerase catalyses elongation during 259 260 261 263 (b, c) Both options (b) and (c) are correct. 264 265 266 267 In eukaryotes, the regulation of gene expression is exerted at transcriptional level (formation of primary transcript), processing level (regulation of splicing), transport of mRNA from nucleus to the cytoplasm and translational level. While, in prokaryotes, control of the rate of transcriptional initiation is the predominant site for control of gene expression. (a) When lactose is present, it act as an inducer and binds to the repressor and inactivates it. This repressor fails to bind to operator. Therefore, the RNA polymerase binds to the promoter and transcript lac mRNA thus switching on the lac operon and allowing transcription to proceed. (d) Option (d) is correct. In a transcription unit, the activity of RNA polymerase at a given promoter is regulated by interaction with accessory proteins, which affects its ability to recognise start sites. These regulatory proteins can act both positively (activators) and negatively (repressors). (a) Chromosome 1 was the last completed chromosome, sequenced two decades after the beginning of the human Genome Project (hGP). It is designated as the largest human chromosome. (c) The human chromosomes having the highest and least number of genes, respectively are chromosome 1 with 2968 genes and chromosome-Y with 231 genes. Answers & Explanations 262 transcription. During elongation RNA polymerase ‘walks’ along one strand of DNA known as the template strand in the 3’ → 5’ direction. For each nucleotide in the template RNA polymerase adds a matching (complementary) RNA nucleotide to the 3’ end of the RNA strand. It associates transiently with initiation factor (σ) and termination factor (ρ ) to initiate and terminate the transcription, respectively. (b) In mRNA of eukaryotes exons appear, but introns do not. This is because introns are intervening or non-coding sequences and exons are coding or expressed sequences. Through splicing introns are removed and exons are joined to form mRNA. (a) To initiate translation, the mRNA first binds to the smaller ribosomal subunit. Ribosome consists of structural RNAs and about 80 different proteins. In its inactive state, it exist as two subunits, a large subunit and a small subunit. When the smaller subunit encounters the mRNA, the process of translation of the mRNA to protein begins with the binding of the mRNA to the smaller ribosome unit. (b) The first base of anticodon in 5′ → 3′ direction binds with the third base in codon (reading in 5′ → 3′ direction). Thus, if the base sequence in codon of mRNA is 5′ – AUG – 3′ the complementary anticodon will be 3′ – UAC – 5′ or 5′ – CAU – 3′. (b) AA-binding site (amino acid binding site) lies at the 3′ end opposite the anticodon and has CCA-OH group. Thus, the site where amino acid attaches to the tRNA is the 3′ end of the tRNA molecule. www.mediit.in CHAPTER > 07 Evolution NEET KEY NOTES Å The origin of life is considered a unique event in the history of universe. The study of history of life forms on the earth is called evolutionary biology. Å Evolution is the process that results in heritable changes in population spread over many generations leading to diversity of organisms on earth. Origin of Life Å It is considered a unique event in the history of our universe. Å Our universe is about 20 billion years old. It comprises of huge clusters of galaxies. Å Various theories given by different thinkers and scientists to explain origin of life are described below Å The Big Bang theory attempted to explain the origin of universe. According to this theory, a single huge explosion resulted in universe expansion, decreased temperature, condensation of gases, formation of hydrogen and helium, etc., which resulted in formation of galaxies. Å Earth is about 4.5 billion years old. Å Life appeared 500 million years after the formation of earth. Å Theory of special creation states that God created life by his divine act of creation. Å Theory of cosmic panspermia (by early Greek thinkers) states that the spores or panspermia came from outer space and developed into living forms. Å Theory of spontaneous generation states that the life originated from decaying and rotting matter like straw, mud, etc. Louis Pasteur rejected the theory of spontaneous generation and demonstrated that life came from pre-existing life and gave theory of biogenesis. Å Theory of chemical evolution or Oparin-Haldane theory states that life originated from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) and the formation of life was preceded by chemical evolution. Å The conditions on the earth that favoured chemical evolution were very high temperature (800ºC), volcanic storms and reducing atmosphere that contained CH4 , NH3 , water vapours, etc. Å In 1953, SL Miller and his student H Urey created primitive earth conditions in the laboratory and provided experimental evidence for chemical evolution. They clearly demonstrated that electrical discharges or UV radiations or both can create organic compounds from mixture of gases ( CH4 , NH3 and H2 in the ratio of 2 : 1 : 2 and water vapours) in the experiment. Origin of First Cell Å First non-cellular life form originated 3 billion years ago. These molecules were like RNA, protein and polysaccharides inside a self-replicating metabolic capsule which later reproduced its molecules. Å Cellular life form first evolved about 2000 million years ago. These were single-celled and formed in aquatic environment. Å This form of abiogenesis, i.e. the first form of life arose slowly through evolutionary forces from non-living molecules, was accepted by many scientists. Biological Evolution Å It is the process of inheritance of genetic changes over several generations. Unlike chemical evolution, biological evolution happens when organisms could replicate. It took place in following steps – Coacervates formation, formation of protobionts, origin of prokaryotes and eukaryotes. Å Coacervates were aggregate of organic biomolecules, surrounded by film of water molecules. They lack definite membrane, but do exhibit some life like characters. Å Microspheres were the non-living collections of organic macromolecules double-layered and can be formed from proteinoids, by heating a mixture of amino acids at 180ºC. Å The first organisms originated in reducing (oxygen free) atmosphere were anaerobes (able to respire in the absence of oxygen). They were called heterotrophs because they were dependent on pre-existing organic molecules for obtaining nutrition. Some of them might have evolved into autotrophs. Å The doctrine of organic evolution states that the present complex organisms (eukaryotes) have been produced by gradual changes in the earlier simpler forms (prokaryotes) of life over ages. www.mediit.in Master The NCERT > Biology (Vol-II) 162 Å Charles Darwin during a sea voyage on his ship HMS Beagle concluded that existing living forms share similarities among themselves and with life forms that existed million of years ago. n Evidences of Evolution Evidences that the evolution of life forms took place on earth came from palaeontology, comparative anatomy and morphology, biochemical evidences and biogeographical evidences. Å Palaeontology is the study of fossils in different sedimentary layers, indicating the geological period in which they existed. Å Geological time scale is a chronological order or history of evolution based upon the study of fossils. It has been divided into eras, periods and epochs. Å Embryological evidences These were given by Ernst Haeckel. He observed structures common in embryonic stage of all vertebrates, like presence of gill slits in all vertebrates embryo including human, but these were functional only in fish and absent in all other adult vertebrates. However, this proposal was disapproved by Karl Ernst von Baer. Å Biochemical similarities These are seen in proteins and genes performing a given function among diverse organisms. This gives clue to common ancestry among diverse organisms. Å Comparative anatomy and morphology show similarities and differences among the organisms of today and those of earlier times. n n n Å Various theories regarding evolution of species, i.e. biological evolution have been postulated by different evolutionists. Some of them are as follows Lamarckism Å Lamarckism (‘Inheritance of Acquired Characters in Organisms’) is given by Lamarck in 1809. It states that changes in structure or function of organ acquired during an individual’ lifetime in response to changes in the environment are inherited by its offspring. Major postulates of this theory are as follows Å Internal vital force Å Effect of environment and new needs Å Use and disuse of organs Å Inheritance of acquired characters This theory was rejected by August Weismann (1892) who proposed the ‘Theory of Continuity of Germplasm’ that states characters influencing germ cells are only inherited. Å Neo-Lamarckism proposed that environment influences an organism directly or indirectly (i.e. produced variation) and changes its heredity, only those variations are passed on to next generation which affects germ cells. Analogous organs are the organs which show superficial resemblance and perform similar function, but have different internal structure, e.g. flippers of penguins and dolphins. These organs suggest occurrence of convergent evolution. Vestigial organs are non-functional organs, which were functional in the ancestors of present organisms, e.g nictitating membrane (3rd eyelid), coccyx, etc., in humans. Adaptive radiation It is the process of evolution of different species in a given geographical area starting from one point and radiating to other habitats, e.g. Darwin finches, Australian marsupials, etc. NEET Adaptive convergence in mammals Australian marsupials and placental mammals in North America provide another example of convergent evolution. Despite the temporal and geographical separation, marsupials in Australia and placental mammals in North America have produced varieties of species living in similar habitat with similar ways of living. They are not related, but resemble each other because they fill similar niches in each continent. Theories of Evolution Homologous organs are the organs which show same structure, but different functions, e.g. forelimbs of whales, bats and cheetah. These organs suggest occurrence of divergent evolution. Biogeographical evidences It suggests that species restricted to a region, develop unique features. Also, species present in widely separated regions show similarity of ancestry. Habitat isolation had probably restricted these organisms to a particular geography on the earth. This can be explained with the help of following processes n n Adaptive convergence/convergent evolution When more than one adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats) and two or more groups of unrelated animals come to resemble each other for similar mode of life or habitat, it is called adaptive convergence or convergent evolution. Darwinism Å Darwinism (Theory of Natural Selection) is given by Charles Darwin in 1859. The essence of this theory is natural selection. The environment selects those individuals which are better fitted, and have adaptive ability to survive and reproduce. KEY NOTES www.mediit.in 163 CHAPTER 07 > Evolution Å The two key concepts of Darwinian theory of evolution are described as follows n p 2 + 2pq + q 2 = 1 (i) Branching descent is defined as a process by which new species originate from a single common descent. where, p and q are individual frequencies of different alleles. This is a binomial expansion of ( p + q) 2 . When frequency measured, differs from expected values, the difference indicates the extent of evolutionary change. (ii) Natural selection states that organisms better adapted to environment are selected by nature and they survive, reproduce and pass their characters to next generations. It leads to speciation (formation of new species). n An example of natural selection is industrial melanism in peppered moths of England. Before industrialisation (in 1850s), white peppered moths were able to escape predation due to trees covered by white coloured lichen, but after industrialisation, black peppered moths increased and selected by nature due to trees covered by black soot present in that region, i.e. the proportion was reversed. Mutation Theory of Evolution (Mechanism of Evolution) Å In 1901, Hugo de Vries carried out experiments on evening primrose plant (Oenothera lamarckiana) and proposed the mutation theory of evolution. Å This theory states that the evolution occurs by the sudden large differences in the population. He believed that mutation is the only cause of evolution and not the minor heritable variations that Darwin talked about. Å He stated that the mutation caused speciation and named it saltation (single step large mutation). Mutations are random and without directions, while, Darwinian variations are small and directional. Modern Synthetic Theory of Evolution Å Å With progress in genetics, the sources of variation were explained and Darwin’s theory was modified. Now, the most accepted theory of evolution is known as modern synthetic theory of evolution, designated by Huxley in 1942 in which the origin of species is based on the interaction of genetic variation in a population, natural selection and reproductive isolation. Hardy-Weinberg Principle Å This principle states that allele frequencies in a population are stable and are constant from generation to generation, i.e. gene pool is constant. Å It occurs when population is large and there is random mating among members of the population. This is called genetic equilibrium or Hardy-Weinberg equilibrium. Sum total of all allelic frequencies is 1. It can be expressed by the following equation n Any fluctuation in genetic equilibrium leads to evolution. Factors Affecting Hardy-Weinberg Equilibrium The factors that affect Hardy-Weinberg equilibrium are given below Å Gene migration or Gene flow Due to migration, new genes or alleles are added to the new population and these are lost from the old population, in turn changing the frequencies. There would be a gene flow if this gene migration happens multiple times. So, gene flow changes the frequency of allele. Å Genetic drift The changes occurring in frequencies by chance are called genetic drift. Sometimes due to changes in allele frequency in new population, some different species are formed. This is called founder effect and the original drifted population is called founder. Å Mutations These occur randomly and at very slow rates. They lead to new phenotypes and due to the considerable genetic variation, speciation occurs. Genetic recombination During gametogenesis, crossing over in meiosis leads to new combination of genes. Å Å Natural selection It occurs due to the inheritance of variations, which leads to the survival of the fittest. So, if above five factors are absent in a population it means there is no evolution going on in that population. It has following effects n n n Stabilisation Large number of individuals acquire mean character value. Directional change Large number of individuals acquire value other than mean character value. It means natural selection is taking place in one direction. Disruption More individuals acquire peripheral character value at both ends of the distribution curve. NEET KEY NOTES www.mediit.in Master The NCERT > Biology (Vol-II) 164 Here, natural selection takes place in two different directions. Å Peak gets higher and narrower Phenotypes favoured by natural selection Å (a) Medium-sized individuals are favoured Peak shifts in one direction Å Å (b) Number of individuals with phenotype Two peaks formed (c) Diagrammatic representation of the operation of natural selection on different traits, (a) Stabilising, (b) Directional and (c) Disruptive A Brief Account of Evolution Å Å Å About 2000 million years ago (mya), the first cellular form of life appeared on earth. Some of these cells had the ability to release O2 by splitting water molecule with the help of solar energy. Slowly, single-celled organisms became multicellular life forms. Evolution of Plants Plant’s evolution occurred before animals. Å Bryophytes were the first plants to colonise land and were evolved before the vascular plants like pteridophytes and gymnosperms. Å Vascular plants first originated in Silurian period. Å Existence of sea weeds and few plants was reported around 320 million years ago. Å Herbaceous lycopods and arborescent lycopods evolved from Zosterophyllum of Palaeozoic era. Å Psilophyton is the common ancestor for horsetails, ferns and gymnosperms. Evolution of Animals Å First animals were invertebrates, which were formed around 500 mya. Å Jawless fish and amphibious fish with stout and strong fins originated around 350 mya. Å The first amphibians and ancestors of modern day frogs were lobefins (Coelacanth). In 1938, it was caught in South Africa which was thought to be extinct. It is a living fossil. Å Reptiles were evolved from amphibians. They lay thick-shelled eggs that do not dry up in the sun like those of amphibians. Reptiles dominated the earth, around 200 mya. NEET Å Land reptiles were dinosaurs of which Tyrannosaurus rex (about 20 feet in height) was the biggest. Some land reptiles went back to water and evolved as fish-like reptiles, e.g. Ichthyosaurs. About 65 mya, dinosaurs disappeared from the earth. In Triassic period, mammals appeared and the first mammals were like shrews. Mammals were viviparous and protected their unborn young ones inside the mother’s body. Mammals were more intelligent in sensing and avoiding the danger. Before continental drift, horse, hippopotamus, bear, rabbit, etc., were present in South America, but afterward when South America joined North America, these animals were overhidden by North American fauna. Origin and Evolution of Man The fossil evidence clearly indicates that origin of man occurred in Central Asia, China, Java and India (Shivalik hills). Thus, the common ancestor of apes and man was Dryopithecus. Å The next stage was Ramapithecus in the hominid evolution. Both were hairy and walked like gorillas and chimpanzees. Few fossils of man-like bones have been discovered in Ethiopia and Tanzania. Å These revealed hominid features leading to the belief that around 3-4 mya, man-like primates walked in Eastern Africa. The human evolution took place as follows Å Human Ancestors Time of Origin Dryopithecus 20-25 mya Ape-like, hairy, ate soft fruits and leaves. Arms and legs of same length, large brain. Ramapithecus 14-15 mya More man-like, walked more erect, teeth-like modern man. Australopithecus 2 mya (The first ape man) General Feature Probably lived in East African grasslands and ate fruits, hunted with stones, weapons, brain capacity was 400-600 cc. Homo habilis (Handy man) 1.2-1.5 mya Fossils found in East Africa , first hominid, i.e. human-being like, brain capacity 650-800 cc, did not eat meat. Homo erectus (Java man) 1.5 mya Fossils found in Java in 1891, brain capacity 900 cc, probably ate meat. Homo sapiens sapiens neanderthalensis (Primitive man) 1,00,000-40,000 Known as neanderthal man. Fossils years ago found in East and Central Asia, brain size 1400 cc, used hides to protect body, buried their dead body. They became extinct 25,000 years ago. Homo sapiens sapiens (Modern man) 75,000-10,000 years ago (ice age) Arose in Africa, developed cave art around 18,000 years ago, agriculture started around 10,000 years back and thus human settlement and civilisation started. KEY NOTES www.mediit.in 165 CHAPTER 07 > Evolution Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Origin of Life and Evolution of Life Forms 1 Evolutionary biology is (a) (b) (c) (d) the study of history of life forms on earth study of pedigrees of life forms on earth equivalent to demography equivalent to anthropology 2 According to one of the most widely accepted theories, earth’s atmosphere before origin of life consisted of a mixture of (a) (b) (c) (d) O3 , CH4 , O2 and H2 O O3 , NH3 , CH4 and H2 O H2 , CO2 , NH3 and CH4 CH4 , NH3 , H2 and H2 O vapours 3 Which theory arguments that life on earth came from outer space through spores? (a) (b) (c) (d) Theory of panspermia Cosmozoic theory Spore theory More than one option are correct 4 For a long time, it was believed that life came out of decaying and rotting matter like straw, mud, etc. This was the theory of (a) catastrophism (c) panspermia (b) spontaneous generation (d) chemogeny 5 Who discarded the theory of spontaneous generation once and for all? (a) Louis Pasteur (c) Spallanzani (b) Francesco Redi (d) Aristotle 6 Who showed that life did not evolve from killed yeast in pre-sterilised flasks? (a) Oparin (c) Louis Pasteur following mixtures in his experiment (a) (b) (c) (d) CH4 , NH3 , H2 and water vapours at 800ºC H2 , O2 , N2 and water vapours at 200ºC H2 , O2 , C2 and water vapours at 2000ºC CH4 , NH3 , O2 and water vapours at 500ºC 10 What did Miller obtained from his experiment? (a) Amino acids (c) Nitrogen bases (b) Organic compounds (d) All of these 11 On early earth, organic acids were produced by the combination of H 2 with (a) ammonia and methane (b) hydrogen (c) organic matter (d) sulphates and nitrates 12 The first non-cellular forms of life that originated 3 billion years back was/were (a) protein (c) RNA (b) polysaccharide (d) All of these 13 The first single cell-like structure initially appeared in (a) air (b) mountain (c) ocean (d) soil 14 The sequence of origin of life may be (a) Inorganic materials → Organic materials → Colloidal aggregate → Eobiont → Cell (b) Organic materials → Inorganic materials → Colloidal aggregate → Eobiont → Cell (c) Inorganic materials → Organic materials → Eobiont → Cell → Colloidal aggregate (d) Organic materials → Inorganic materials → Eobiont → Cell → Colloidal aggregate 15 The given diagram represents Miller’s experiment. (b) Haldane (d) Miller 7 Who proposed that the first form of life could have come from pre-existing non-living organic molecules and it precedes chemical evolution? (a) (b) (c) (d) 9 Miller synthesised simple amino acids from one of the Choose the correct combination of labelling for A, B, C and D. A B SL Miller Oparin and Haldane Charles Darwin Alfred Wallace Mixture of gases C 8 Experimental evidence of chemical evolution was given by (a) Miller (c) Oparin (b) Haldane (d) All of these D www.mediit.in Master The NCERT > Biology (Vol-II) 166 (a) A–Electrodes, B –NH3 + H2 + H2 O + CH4 , C–Condensor, D–U-trap (b) A–Electrodes, B–NH4 + H2 + CO2 + CH3 , C–Vacuum pump, D–U-trap (c) A–Electrodes, B–NH3 + H2 O, C–Condensor, D–Vacuum pump (d) A–Electrodes, B–NH3 + H2 + H2 O + CH4 , C–Boiling water, D–Vaccum pump 16 What was the name of the sail ship used by Charles Darwin during his sea voyage? (a) HMS Beagle (c) HMS Eagle (b) HSM Beagle (d) HSM Eagle 17 According to Charles Darwin’s observations (a) existing life forms share similarities to the life forms that existed million of years ago (b) life forms evolve gradually (c) any population has built in variations which enable them to survive in natural conditions (d) All of the above 18 According to Darwin, those who are better fit in an environment, (a) (b) (c) (d) leave more progeny than others leave less progeny than others are eradicated rapidly due to competition None of the above 19 Theory of natural selection as the mechanism of evolution was given by (a) Lamarck (c) Alfred Wallace (b) Darwin (d) JBS Haldane 20 Scientist who also came to the similar conclusions around the same time of Charles Darwin was (a) (b) (c) (d) Alfred Wallace Hugo de Vries TH Morgan Oparin and Haldane 21 Malay Archipelago is (a) (b) (c) (d) a group of islands visited by Wallace a research paper on evolution written by Wallace a research paper on ecology written by Wallace a group of organism studied by Wallace 22 The conclusions drawn by Darwin and Wallace were (a) All existing life forms share similarities and common ancestors (b) The ancestors of existing life forms were present at different periods in the history of earth (c) The geological history of earth correlates with the biological history of earth (d) All of the above TOPIC 2 ~ Evidences of Evolution 23 Evidence that evolution of life forms has indeed taken 27 Embryological support for evolution given by Ernst place on earth has come from Haeckel includes the (a) (b) (c) (d) (a) (b) (c) (d) fossil studies (palaeontological evidences) morphological and comparative anatomical studies biochemical studies All of the above 24 Fossils are the remains of (a) (b) (c) (d) hard parts of life forms found in rocks light parts of life forms found in rocks proteins and bones of life forms found in rocks fats and proteins of life forms found in rocks 25 A study of fossils in different sedimentary layers indicates (a) (b) (c) (d) physiological period in which they existed geological period in which they existed conditions in which they were living All of the above 26 Fossils are useful in (a) (b) (c) (d) studying extinct organisms studying history of organisms Both (a) and (b) None of the above presence of hair all over the body in adult human absence of tail bone and presence of wisdom tooth absence of vestigial gill slits in human’s embryo presence of row of vestigial gill slits in embryo of all vertebrates 28 The similarity of bone structure in the forelimbs of many vertebrates is an example of (a) convergent evolution (c) homology NEET 2018 (b) analogy (d) adaptive radiation 29 Which one of the following options gives one correct example each of convergent evolution and divergent evolution? CBSE-AIPMT 2012 (a) Convergent evolution Divergent evolution Eyes of Octopus and mammals Bones of forelimbs of vertebrates (b) Thorns of Bougainvillea and Wings of butterflies and tendrils of Cucurbita birds (c) Bones of forelimbs of vertebrates Wings of butterfly and birds (d) Thorns of Bougainvillea and Eyes of Octopus and tendrils of Cucurbita mammals www.mediit.in 167 CHAPTER 07 > Evolution 30 In the animals, the same structures developed along the different directions due to the adaptations to different needs. This is called (a) convergent evolution (c) disruptive evolution (b) divergent evolution (d) directional evolution 31 Divergent evolution gives rise to (a) homologous organs (c) Both (a) and (b) (b) analogous organs (d) None of these 32 Among the following sets of examples for divergent evolution, select the incorrect option. (a) (b) (c) (d) NEET 2018 Brain of bat, man and cheetah Heart of bat, man and cheetah Forelimbs of man, bat and cheetah Eye of Octopus, bat and man 33 What does presence of homologous organs in different animals indicate? (a) (b) (c) (d) Different ancestry Common ancestry Independent development Dependent development 34 Tendrils of Cucurbita and thorns of Bougainvillea are examples of (a) vestigial organs (c) homologous organs (b) analogous organs (d) homoplasy 35 Which of the following structures is homologous to the wing of a bird? (a) Wing of a moth (c) Flipper of whale CBSE-AIPMT 2015 (b) Hindlimb of rabbit (d) Dorsal fin of a shark 36 Diagram given below indicates (c) phylogenetic structures and represent divergent evolution (d) homologous structures and represent convergent evolution 38 The eyes of Octopus and eyes of cat show different patterns of structure, yet they perform similar function. This is an example of NEET 2013 (a) homologous organs that have evolved due to convergent evolution (b) homologous organs that have evolved due to divergent evolution (c) analogous organs that have evolved due to convergent evolution (d) analogous organs that have evolved due to divergent evolution 39 The process by which organisms with different evolutionary history evolve similar phenotypic adaptations in response to a common environmental challenge, is called NEET 2013 (a) natural selection (b) convergent evolution (c) non-random evolution (d) adaptive radiation 40 Evolutionary convergence is the development of (a) common set of characters in closely related groups (b) common set of characters in the group of different ancestry (c) random mating (d) dissimilar characters in the closely related groups 41 Biochemical similarities are based on study of (a) (b) (c) (d) similarities in carbohydrates of organisms similarities in fat (fatty acid) of organisms similarities in protein and genes of organisms All of the above 42 Change of lighter coloured variety of peppered moths Man Cheetah Whale Bat (Biston betularia) to darker variety in the industrial era occurred due to (a) (b) (c) (d) selection of darker variety for survival deletion of gene industrial carbon deposited on the wings translocation of gene 43 England in 1850s, i.e. before industrialisation set in, it (a) analogous organs (c) convergent evolution (b) homologous organs (d) All of these 37 The wings of a bird and the wings of an insect are CBSE-AIPMT 2015 (a) homologous structures and represent divergent evolution (b) analogous structures and represent convergent evolution was observed that there were more white-winged moths on trees than dark-winged or melanised moths. However, in the collection carried out from the same area, but after industrialisation, i.e. in 1920, there were more dark-winged moths in the same area, i.e. the proportion was reversed. Predict the possible reason for such change. (a) (b) (c) (d) Natural selection Artificial selection Conditional selection Divergent selection www.mediit.in Master The NCERT > Biology (Vol-II) 168 46 Industrial melanism is an example of 44 The peppered moth (Biston betularia), the black-coloured form becomes dominant over the light-coloured form of moth in England during industrial revolution. This is an example of AIIMS 2018 (a) appearance of the darker-coloured individuals due to very poor sunlight (b) protective mimicry (c) inheritance of darker colour character acquired due to the darker environment (d) natural selection whereby the darker forms were selected 45 Natural indicator of industrial pollution is (a) algae (b) fungi (c) lichen (d) bacteria CBSE-AIPMT 2015 (a) neo Darwinism (c) mutation (b) natural selection (d) neo Lamarckism 47 Example of anthropogenic evolution is (a) (b) (c) (d) selection of resistant microbes to pesticides antibiotic resistant eukaryotic cells Industrial melanism is Biston betularia All of the above 48 Evolution is (a) (b) (c) (d) discontinuous process stochastic process Both (a) and (b) non-essential process TOPIC 3 ~ Adaptive Radiation 49 Development of different functional structures from a 55 When more than one adaptive radiation appeared to common ancestral form is called have occurred in an isolated geographical area, it is (a) differential evolution (b) adaptive radiation (c) non-adaptive radiation (d) regressive evolution (a) (b) (c) (d) 50 The process by which different type of finches were evolved in Galapagos islands is a consequence of (a) (b) (c) (d) adaptive radiation geographic similarity geographic dissimilarity adaptive convergence convergent evolution divergent evolution natural selection genetic drift 56 Identify what is indicated in the given diagram? 51 The original finches from which other finches arose on Galapagos island were (a) seed-eating (c) vegetarian (b) insectivorous (d) carnivorous Common Ancestor 52 Which one of the following aspects of evolution is shown by Darwin’s finches? (a) (b) (c) (d) Biogeographic evidence Industrial melanism Biochemical evidence Embryological evidence 53 The diversity in the type of finches and adaptation to different feeding habits on the Galapagos islands, as observed by Darwin, provides an evidence of (a) (b) (c) (d) origin of species by natural selection intraspecific variation intraspecific competition interspecific competition 54 Australian marsupials are the example of (a) (b) (c) (d) homologous radiation analogous radiation adaptive radiation convergent radiation I. II. III. IV. Recombination Adaptive radiation Ecological succession Different species of penguins by mutation Choose the correct option. (a) (b) (c) (d) Only I Only III Only IV Only II www.mediit.in 169 CHAPTER 07 > Evolution 57 Identify what the given diagram indicates? adaptive radiation? Tasmanian wolf Koala bear Australian Marsupials Marsupial rat Kangaroo (a) (b) (c) (d) Convergent evolution Divergent evolution Recapitulation Parallel evolution 58 The classical example of adaptive radiation in development of new species is (a) (b) (c) (d) Darwin’s finches marsupials of Australia locomotion in mammals All of the above 59 Example of convergent evolution is (a) (b) (c) (d) 60 Which of the following is not an examples of Darwin finches and marsupial mouse Placental wolf and Tasmanian wolf Placental wolf and Darwin finches Tasmanian wolf and marsupial mole (a) (b) (c) (d) Wombat, numbat, flying phalanger Darwin’s finches Different mammals in other parts of world Lemur and spotted cuscus 61 In Australia, marsupials and placental mammals have evolved to share many similar characteristics. This type of evolution may be referred to as NEET 2019 (a) (b) (c) (d) adaptive radiation divergent evolution cyclical evolution convergent evolution 62 A population of a species invades a new area. Which of the following conditions will lead to adaptive radiation? NEET 2019 (a) Area with large number of habitats having very low food supply (b) Area with a single type of vacant habitat (c) Area with many types of vacant habitats (d) Area with many habitats occupied by a large number of species TOPIC 4 ~ Biological Evolution and its Mechanism 63 What is meant by the term ‘Darwin fitness’? (a) (b) (c) (d) Ability to survive and reproduce High aggressiveness Healthy appearance Physical strength 64 Survival of the fittest is possible due to the (a) (b) (c) (d) overproduction favourable variations environmental changes inheritance of acquired characters 65 Darwinian fitness can be estimated by (a) how long different individual in a population survive (b) number of offspring produced by different individuals in population (c) individual have a large size in population (d) species recover after mass extinction 66 Which of the following are the two key concepts of Darwinian theory of evolution? (a) (b) (c) (d) Genetic drift and mutation Adaptive radiation and homology Mutation and natural selection Branching descent and natural selection 67 Which concept was not included in Charles Darwin’s theory of natural selection? (a) (b) (c) (d) Survival of the fittest Struggle for existence Overproduction of offspring Punctuated equilibrium 68 What is the difference between natural selection and sexual selection? (a) (b) (c) (d) Sexual selection occurs during sexual intercourse Natural selection is a type of sexual selection Sexual selection is an example of natural selection Sexual selection occurs within demes 69 Which of the following situations would most likely result in the highest rate of natural selection? (a) (b) (c) (d) Reproduction by asexual method Low mutation is an stable environment Little competition Reproduction by sexual method 70 According to Darwin, the organic evolution is due to the (a) (b) (c) (d) intraspecific competition NEET 2013 interspecific competition competition within closely related species reduced feeding efficiency in one species due to the presence of interfering species www.mediit.in Master The NCERT > Biology (Vol-II) 170 71 Which one of the following was not explained by 76 Which of the following differences between Darwinism? Lamarckism and Darwinism is incorrect? (a) (b) (c) (d) Lamarckism Darwinism (a) It does not consider struggle for existence Struggle for existence is very important in this theory (b) Only useful variations are transferred to the next generation All the acquired characters are inherited to the next generation. (c) Neglects survival of the fittest Based on survival of the fittest (d) None of the above Natural selection Struggle for existence Arrival of the fittest Origin of species 72 Which of the following factors was not taken into account by Darwin in his theory of natural selection? (a) (b) (c) (d) Struggle for existence Discontinuous variations Parasites and predators as natural enemies Survival of the fittest 73 Lamarck’s theory of evolution is also known as (a) (b) (c) (d) theory of use and disuse of organs theory of genetic characters theory of spontaneous characters theory of impose characters 74 Who proposed that long neck of giraffes evolved due to foraging of leaves on tall trees? (a) (b) (c) (d) Lamarck Darwin Malthus Aristotle 75 What was the Lamarck’s explanation for long necked giraffes? (a) (b) (c) (d) Stretching of necks over many generations Short neck suddenly changed into long one Natural selection Mutation 77 Hugo de Vries put forth his idea of mutation by his work on (a) pea plant (c) evening primrose (b) Drosophila (d) maize plant 78 Who proposed the concept of saltation? (a) Darwin (c) de Vries (b) Mendel (d) Thomas Malthus 79 What does the term ‘Saltation’ imply? (a) (b) (c) (d) Excess of species at a given area Reduced number of species due to saline environment Occurrence of variations gradually, step by step Single step large mutations 80 Variations caused by mutation, as proposed by Hugo de Vries are NEET 2019 (a) random and directionless (b) small and directional (c) small and directionless (d) random and directional TOPIC 5 ~ Hardy-Weinberg Principle 81 Hardy-Weinberg principle is the (a) (b) (c) (d) stable allele frequency in a population genetic structure of an evolving population varying allele frequency in a population phenotypic structure of a non-evolving population 82 Genetic equilibrium refers to the phenomenon in which (a) (b) (c) (d) the trait remains constant in a population the total genes remain constant in a population the total genes keeps on varying in a population traits keeps on varying in a population 83 Change in gene frequency of a population means (a) (b) (c) (d) evolution is in progress Hardy-Weinberg equilibrium is not achieved there may be a selection, migration or mutation All of the above 84 Hardy-Weinberg principle can be expressed as (a) p 2 − 2 pq − q 2 = 1 (b) p 2 + 2 pq + q 2 ≥ 1 (c) p 2 + 2 pq + q 2 ≤ 1 (d) p 2 + 2 pq + q 2 = 1 85 A gene locus has two alleles A, a. If the frequency of dominant allele A is 0.4, then what will be the frequency of homozygous dominant, heterozygous and homozygous recessive individuals in the population? NEET 2019 (a) 0.16(AA); 0.24(Aa); 0.36(aa) (b) 0.16(AA); 0.48(Aa); 0.36(aa) (c) 0.16(AA); 0.36(Aa); 0.48(aa) (d) 0.36(AA); 0.48(Aa); 0.16(aa) www.mediit.in 171 CHAPTER 07 > Evolution 86 Which of the following conditions represents the extent of evolutionary change in Hardy-Weinberg principle? 93 Name the type of natural selection depicted in the given diagram (type I, type II and type III). Type I (a) Value of ( p + q )2 (b) Difference between measured value and expected value (c) Sum of measured value and expected value (d) This principle cannot predict the extent of evolutionary change (d) q 2 e at in im El Mean Conserved by selection Eliminated CBSE-AIPMT 2015 (c) pq Conserved d Eliminated heterozygous individual is represented by (b) 2 pq Mean Conserved 87 In Hardy-Weinberg equation, the frequency of (a) p 2 Type II Mean Mean Eliminated 88 The tendency of population to remain in genetic equilibrium may be disturbed by NEET 2013 (a) random mating (b) lack of migration (c) lack of mutations (d) lack of random mating Type III Mean Conserved 89 Identify the phenomenon in which a new set of Eliminated population is formed from the set of existing population due to the random excessive change in the allele frequency. (a) Founder effect (c) Bottle-neck effect (b) Genetic drift (d) All of these 90 Genetic drift operates in (a) (b) (c) (d) Eliminated Mean Mean Conserved CBSE-AIPMT 2015 small isolated population large isolated population non-reproductive population slow reproductive population 91 ‘XX’ is a type of selection process in evolution that promotes population changes in one particular direction. ‘XX’ favours small or large sized individuals mean size of population changes. Identify ‘XX’. (a) (b) (c) (d) Stabilising selection Directional selection Disruptive selection None of the above Type I Disruptive Directional Stabilising Stabilising Type II Directional Disruptive Directional Disruptive Type III Stabilising Stabilising Disruptive Directional 94 Artificial selection to obtain cows yielding high milk output represents 92 ‘PP’ is a type of selection that favours both small sized and large-sized individuals. ‘PP’ eliminates most of the members with mean expression, so as to produce two peaks in the distribution of the tract that many leads to the development of two different populations. Identify ‘PP’. (a) Disruptive selection (c) Directional selection (a) (b) (c) (d) (b) Stabilising selection (d) None of these NEET 2017 (a) stabilising selection as it stabilises this character in the population (b) directional as it pushes the mean of the character in one direction (c) disruptive as it splits the population into two, one yielding higher output and the other lower output (d) stabilising followed by disruptive as stabilises the population of produce higher yielding cows www.mediit.in Master The NCERT > Biology (Vol-II) 172 95 In a large randomly mating population, only one person in 10,000 is an albino. What will be the frequency of carrier person of albinism? (a) 1 in 100 (b) 99 in 10,000 (c) 2 in 10,000 (d) 1 in 50 96 Allopatric speciation occurs when (a) genetically related populations inhabit widely separated geographical area (b) genetically unrelated populations inhabit widely separated geographical area (c) genetically related populations inhabit the same geographical area (d) genetically unrelated populations inhabit the same geographical area TOPIC 6 ~ A Brief Account of Evolution 97 Choose the incorrect pair. (a) Invertebrates were formed and active – By 500 mya (b) Seaweeds existed – Around 320 mya (c) First organisms that invaded land – Single-celled animals (d) Fish with stout and strong fins – Around 350 mya 98 Name the animal that evolved into the first probable amphibians and lived on both land and water. (a) Whale (c) Amphioxus (b) Coelacanth (lobefins) (d) Balanoglossus 99 There was no life in (a) Cenozoic era (c) Palaeozoic era (b) Mesozoic era (d) Azoic era 100 Which period in geological time scale is considered the golden era of fish? (a) Mississippian (c) Devonian Jurassic period. This period was also marked for the evolution of higher insects and angiosperms, conifers, cycads, etc. Jurassic period belongs to which era? (b) Palaeozoic (d) Proterozoic 102 During which period did the first seed plant appear? (a) Silurian (c) Carboniferous (b) Devonian (d) Cretaceous 103 The Cenozoic era is often designated as (a) age of fish (c) age of mammals (a) Mesozoic (c) Palaeozoic (b) age of reptiles (d) age of amphibians (a) (b) (c) (d) Palaeozoic → Archaeozoic → Cenozoic Archaeozoic → Palaeozoic → Proterozoic Palaeozoic → Mesozoic → Cenozoic Mesozoic → Archaeozoic → Proterozoic 109 First dinosaurs and first egg-laying mammals originated in (a) Jurassic period (c) Permian period (b) Azoic era (d) Mesozoic era given diagram. Lizards Turtles Quaternary (b) Equus (d) Columba 106 Mesozoic era is called the age of (a) fishes (c) reptiles (b) amphibians (d) birds Birds Tuataras Crocodiles Snakes Mammals 0 50 ...C... Dinosaurs (extinct) Cretaceous 100 ...B... 150 Triassic 200 Therapsids (extinct) Thecodonts (extinct) ...A... 250 Pelycosaurs (extinct) Sauropsids Synapsids Carboniferous 300 350 105 Which of the following is an extinct animal? (a) Protopterus (c) Archaeopteryx (b) Triassic period (d) Cambrian period 110 Identify the geographical periods ( A, B , C ) in the 104 In which era Protozoa, sponge and algae originate? (a) Cenozoic era (c) Proterozoic era (b) Cenozoic (d) Proterozoic 108 The correct order of evolutionary scale is (b) Silurian (d) Jurassic 101 Giant dinosaurs and reptiles predominated during the (a) Cenozoic (c) Mesozoic 107 The most recent era in geological time scale is Early reptiles (extinct) (a) (b) (c) (d) A–Tertiary, B–Jurassic, C–Permian A–Tertiary, B–Permian, C–Jurassic A–Permian, B–Jurassic, C–Tertiary A–Jurassic, B–Tertiary, C–Permian www.mediit.in 173 CHAPTER 07 > Evolution 111 Choose the incorrectly matched pair. (a) (b) (c) (d) 113 In which epoch, only modern humans prevail? Reptiles — Thick-shelled eggs which do not dry up Tyrannosaurus rex — Fish like reptile Dinosaurs — May be evolved into birds Continental drift — South America joined North-America 112 The first viviparous mammals whose fossils are small-sized were like (a) shrews (b) monkeys (c) rats (d) lobefins (a) Pleiostocene (b) Holocene (c) Pliocene (d) Miocene 114 Which phenomena confined the pouched mammals to Australia they survived because of lack of competition from any other mammals? (a) (b) (c) (d) Continental origination Continental shifting Continental drift Continental evolution TOPIC 7 ~ Origin and Evolution of Man 122 Who was more intelligent than modern man, 115 Choose the incorrect pair. (a) Ramapithecus – Man-like (b) Dryopithecus – Ape-like (c) Fossil of man-like bones were discovered – Ethopia and Tanzania (d) Australopithecus – Probably lived in Western Africa desert cave-dweller, had prominent chin and appeared after neanderthal man? (a) Erect man (c) Hominid tool maker (b) Cro-Magnon man (d) First ape man 123 What was the most significant trend in the evolution of modern man (Homo sapiens) from his ancestors? 116 First human like hominid is known as (a) Neanderthal man (c) Dryopithecus (b) Homo habilis (d) Homo erectus 117 Brain (cranial) capacity of Homo habilis was (a) 750-850 cc (c) 650-800 cc (b) 750-800 cc (d) 550-700 cc 118 The fossil finding suggest that closest fossil to Homo habilis was (a) Homo erectus (c) Dryopithecus (b) Homo sapiens (d) Neanderthal man 119 The extinct human who lived 10,00,00 to 40,000 years ago, in Europe, Asia and parts of Africa, with short stature, heavy eyebrows, retreating fore heads, large jaws with heavy teeth, stocky bodies, a lumbering gait and stooped posture was CBSE-AIPMT 2012 (a) Homo habilis (b) Neanderthal human (c) Cro-Magnon human (d) Ramapithecus 120 Homo sapiens, neanderthalensis and Cro-Magnon man, probably originated from (a) Homo erectus (c) Ramapithecus (b) Homo habilis (d) Proconsul 121 The difference between Homo sapiens and Homo erectus was (a) Homo sapiens originated in Africa, while Homo erectus originated in Asia (b) Homo erectus were much smaller in size than Homo sapiens (c) Homo erectus stayed in Africa, while Homo sapiens did not (d) the size of the brain of Homo erectus was smaller than that of Homo sapiens CBSE-AIPMT 2011, 12 (a) Shortening of jaws (b) Binocular vision (c) Increasing brain capacity (d) Upright posture 124 Who used hides to protect their body and buried their dead? (a) Neanderthal man (c) Australopithecus (b) Homo habilis (d) Dryopithecus 125 Homo sapiens most likely arose in (a) India (b) America (c) England (d) Africa 126 Homo sapiens arose during (a) (b) (c) (d) ice age between 75000-10000 years ago continental drift between 75000-10000 years ago continental drift between 75000-5000 years ago ice age between 50000-10000 years ago 127 The chronological order of human evolution from early to the recent stages is (a) Ramapithecus → Australopithecus → Homo habilis → Homo erectus (b) Australopithecus → Ramapithecus → Homo habilis → Homo erectus (c) Pithecanthropus pekinensis → Homo habilis → Homo erectus (d) Australopithecus → Ramapithecus → Pithecanthropus pekinensis → Homo erectus 128 The diagram given here shows the skull of two different mammals. Choose the most appropriate difference between A and B. A (a) (b) (c) (d) B Skull A has more teeth than skull B Skull A has more brain capacity than skull B Skull A is of a human and skull B is of an ape Skull A is of an ape and skull B is of human www.mediit.in NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Direction (Q. No. 129-143) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason(R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 129 Assertion (A) Theory of chemical evolution 130 131 132 133 134 135 proposed that life came from pre-existing non-living organic molecules. Reason (R) Primitive earth conditions led to the production of organic molecules. Assertion (A) The theory of special creation states that God created life by his divine act of creation. Reason (R) Louis Pasteur rejected the theory of spontaneous generation. Assertion (A) Earth is about 15 billion years old. Reason (R) Life appeared 500 million back after the formation of earth. Assertion (A) Earliest organisms that appeared on the Earth were non-green and presumably anaerobes. Reason (R) The first autotrophic organisms were the chemoautotrophs that never released oxygen. Assertion (A) Microspheres were aggregates of organic biomolecules surrounded by film of water molecule. Reason (R) Coacervates lack definite membrane, but do exhibit some life like characters. Assertion (A) Ernst Haeckel supported the embryological similarities as an evidence of evolution. Reason (R) The embryos of all vertebrates including humans develop a row of vestigial gill slits which are absent in adult vertebrates. Assertion (A) Natural selection is an outcome of the differences in survival and reproduction among individuals that show variations in one or more traits. 136 137 138 139 Reason (R) Adaptive forms of a given trait tend to become more common. Less adaptive ones becomes less common or disappear. Assertion (A) Whales and mammals share similarities in the pattern of bones of forelimbs. Reason (R) These organisms suggest occurrence of divergent evolution. Assertion (A) Analogous structures are different in appearance and have same function. Reason (R) Divergent evolution leads to analogy. Assertion (A) Lichens act as pollution indicators. Reason (R) These do not grow in areas that are polluted. Assertion (A) Lichens are symbiotic relationships of algae and viruses. Reason (R) These are sensitive to SO 2 levels in the air. 140 Assertion (A) Hugo de Vries said mutations cause speciation. Reason (R) Mutations are slow changes. 141 Assertion (A) The introduction of new alleles into the local gene pool by interbreeding of migrating individuals with members of local population is called gene migration. Reason (R) If gene migration happens multiple times, it is called gene recombination. 142 Assertion (A) Sudden inheritable changes take place in genome of an organism due to certain factors called mutations. Reason (R) Lamarck’s theory of evolution is popularly called the theory of continuity of germplasm. 143 Assertion (A) Among the primates, chimpanzee is the closest relative of the present day humans. Reason (R) The banding pattern in the autosome number 3 and 6 of man and chimpanzee is remarkably similar. II. Statement Based Questions 144 Which of the following statements about orgin of life is incorrect? (a) The universe is almost 20 billion years old (b) Big Bang theory explained that universe originated by a huge explosion (c) Present day galaxies are formed by the condensation of hydrogen and helium under gravitational pull (d) None of the above www.mediit.in 175 CHAPTER 07 > Evolution 145 Identify the correct statement. (a) Earth was formed about 4.5 billion years ago (b) Early earth had no atmosphere (c) The temperature of universe came down due to its expansion (d) All of the above 146 Which one of the following statements is true regarding the theory of natural selection? (a) (b) (c) (d) It was the first theory of organic evolution It does explain information derived from fossils It has failed to explain the origin of variations It has succesfully explained concept of speciation 147 Which of the following statements would Darwinism most likely disagree with? (a) Individuals within a population vary in the characteristics they possess (b) Evolution is best viewed as a purpose less and nondirectional change over time (c) Natural selection is the mechanism by which biological evolution takes place (d) The fossil record supports the view that biological evolution has occurred 148 Identify the incorrect statement. (a) In natural selection, heritable variations enable better survival (b) Variations due to gene flow changes allele frequency in future generation (c) Gene flow occurs due to multiple gene migration (d) None of the above 149 Which one of the following statements is/are correct about Australopithecus? (a) (b) (c) (d) They essentially ate fruits They hunted with stone weapons They were transitional stage between ape and humans All of the above 150 Which of the following is the correct sequence of events in the origin of life? NEET 2016 I. Formation of protobionts. II. Synthesis of organic monomers. III. Synthesis of organic polymers. IV. Formation of DNA-based genetic systems. Choose the correct option. (a) I, II, III and IV (c) II, III, I and IV (b) I, III, II and IV (d) II, III, IV and I 151 Which of the following statements are correct about the characteristics of protobionts, like microspheres as envisaged in the abiogenic origin of life? I. They were able to reproduce. II. They could separate the combinations of molecules from the surroundings. III. They were partially isolated from the surroundings. IV. They could maintain an internal environment absolutely. Choose the correct option. (a) I and II (c) III and IV (b) II and III (d) I, II, III and IV 152 Which of the following statements stands in favour of abiogenesis? I. Spontaneous generation. II. Origin of viruses and microbes. III. Origin of life from living organisms. IV. Origin of life from non-living matter. The correct statement(s) is/are (a) I and II (c) III and IV (b) II and III (d) Only IV 153 Which of the following statements are the correct pair of homologous organs? I. Hands of man and wings of bat. II. Wings of bat and wings of cockroach. III. Wings of bird and wings of butterfly. IV. Fins of fish and forelimbs of horse. V. Forearm of human and forelimbs of horse. Choose the correct option (a) I and II (b) I and V (c) III and IV (d) IV and V 154 Which of the following statements are correct? I. Wings of insects and birds are homologous organ. II. Wings of bats and birds are homologous organ. III. Wings of insects and bats are analogous. IV. Wings of insects and birds are analogous. Choose the correct option. (a) I and II (c) I and IV (b) I and III (d) II, III and IV 155 Select the incorrect statements. I. Natural selection is essential for evolution. II. Natural selection does not include variations. III. Concept of natural selection was given by Hugo de Vries. IV. Mutation is a sudden inheritable change. V. Synthetic theory is also called Neo-Darwinism theory of evolution. The correct combination is (a) I, II and III (c) III, IV and V (b) II, III and IV (d) II and III 156 Which of the following statements are correct? I. Survival of the fittest is based upon the characteristics that are inherited. II. Darwin’s variations are small and directional. III. The fitness is the end result of the ability to adapt. www.mediit.in Master The NCERT > Biology (Vol-II) 176 IV. Genetic drift is operate in small populations. V. Genetic drift operates in large populations. VI. Presence of genetic drift upsets the Hardy-Weinberg equilibrium. Choose the correct option. (a) I, II, III and IV (c) I, II, III, V and VI (b) IV, V, VI and II (d) I, II, III, IV and VI 157 True statements regarding the genetic drift is/are I. It mostly occurs in smaller populations. II. Certain alleles can be lost forever because of genetic drift. III. Founder effects and bottle neck effects are caused by genetic drift. IV. Mutations are primarily responsible for genetic drift. The correct combination showing true statements is (a) Only I (c) II and IV (b) III and IV (d) All except IV 158 Which of the following statements regarding the evolution of plants and animals are correct? I. Amphibians evolved into reptiles. II. Fish with stout and strong fins could move on land and go back to water. This was about 350 million years ago. III. Giant ferns fell to form coal deposits slowly. IV. About 65 million years ago dinosaurs died out. V. Archaeopteryx is the connecting link between birds and reptiles. The correct combination is (a) I and II (c) V and I (b) III and IV (d) I, II, III, IV and V 159 Mark the correct statements. I. Karl Ernst von Baer noted that embryo never pass through adult stages of other animals and thus discarded Ernst Haeckel’s embryological support for evolution. II. Homology in vertebrate brain indicates common ancestry. III. Theory of acquired character was given by de Vries. IV. After industrialisation, the white moth population decreased due to predators. The correct option is (a) I, II and III (c) II, III and IV (b) I, III and IV (d) I, II and IV 160 Choose the incorrect statements. I. The essence of Darwinian theory about evolution can be seen in the phenomenon of natural selection. II. The rate of appearance of new forms is not linked to the evolution. III. Adaptive ability is a complete evolution. IV. Mutations are random and directionless. Choose the correct option. (a) I and II (c) I and III (b) II and III (d) I and IV 161 When a species gets separated geographically, it evolves separately? Which of the following conditions would determine whether they are now different species? I. They fail to interbreed. II. They failed to give fertile offspring. III. They have different coloured body. IV. They appear morphologically slightly different. Choose the correct combination from given options. (a) I and II (c) III and IV (b) II and III (d) I and IV 162 Choose the correct statements with reference to organic evolution. AIIMS 2018 I. Flippers of whale and wings of bat exhibit analogy. II. Wings of butterfly and wings of bird exhibit homology. III. Organs with dissimilar structure are called analogous organs. IV. Organs with similar structure and origin are called homologous organs. (a) I and IV (c) III and IV (b) I and III (d) II and IV 163 Which of the following statements is correct regarding the evolution of humans? I. The skull of adult chimpanzee is more like adult human skull than baby chimpanzee skull. II. The skull of baby chimpanzee is more like adult human than adult chimpanzee skull. III. Dryopithecus is oldest human like fossil. IV. Dryopithecus was found in Miocene rock of Africa and Europe. The correct option is (a) I and II (b) I and III (c) I and IV (d) II, III and IV 164 Consider the following statements. I. Darwin asserted that heritable variations and better resource utilisation enable an individual to reproduce efficiently. II. Darwinian variations were small and directional select the correct option. (a) I is true, II is false (c) Both I and II are true (b) I is false, II is true (d) Both I and II are false 165 In his theory of evolution, Lamarck explained I. Internal vital force. II. Effect of environment on organisms. III. Inheritance of acquired characters. IV. Use and disuse of organs. www.mediit.in 177 CHAPTER 07 > Evolution Choose the correct combination. (a) I and II (c) I, II and IV (b) II and III (d) I, II, III and IV 166 Which of the following phenomena support the Darwin’s concept of natural selection in organic evolution? I. Development of transgenic animals. II. Production of Dolly. III. Increased prevalance of pesticides has led to pesticide resistance in insects. IV. Industrial melanism. Choose the correct statement. (a) I and II (b) II and III (c) III and IV (d) I and IV 167 Lamarck’s concept of inheritance of acquired characters was discarded by I. Mendel’s laws of inheritance. II. Theory of natural selection. III. Mutational theory. IV. Theory of continuity of germplasm. Choose the correct combination of the given options to complete the given statement. (a) I and II (b) II and III (c) I and IV (d) III and IV 168 Which of the following features are connected with the modern theory of evolution? I. Genetic and chromosomal mutation. II. Genetic recombination and natural selection. III. Reproductive isolation. The correct combination is (a) I and II (c) I and III (b) II and III (d) I, II and III 169 Which of the following statements correctly defines the phenomenon of genetic drift? I. It is random change in gene allele frequency. II. It occurs by chance. III. It is directional. IV. It causes elimination of certain alleles. V. It causes fixation of alleles. The correct combination is (a) I, II and III (c) I, III and V (b) III, IV and V (d) I, II, IV and V 170 Consider the following statements. I. Evolution by natural selection have started when cellular forms of life with differences in metabolic capability originated on earth. II. The essence of Darwinian theory about evolution is natural selection. Select the correct option. (a) I is true, II is false (c) I is false, II is true (b) Both I and II are true (d) Both I and II are false 171 Consider the following statements. I. Microbes are able to grow on new nutrient media due to natural selection. II. Adaptive ability is inherited and has genetic basis. Select the correct option. (a) Both I and II are true (c) Both I and II are false (b) I is true, II is false (d) I is false, II is true 172 Natural selection I. tends to decrease the survival and reproduction of an organism. II. acts on organism phenotype. III. mechanism of evolution explained by Darwin. Which of the following statements are correct? (a) I, II and III (c) II and III (b) I and II (d) I and III 173 Evidence which favours the theory of acquired characters are I. the absence of limbs in snakes. II. the presence of webbed toes in aquatic bird. III. lack of pigments in cave dwelling animals. IV. Darwin finches. V. melanisation peppered moths. Choose the correct option. (a) I and II (c) I, II and IV (b) II and III (d) I, II and III 174 Consider the following statements and choose the correct statements. I. Gene mutations are directional changes in the bases of sequences of genes. II. Bottle neck effect is the fluctuation in population density causing reshuffling of some of the genes in a gene pool in random fashion. III. Founder effect is called as Sewall Wright effect. IV. Modern concept of evolution is also called synthetic theory of evolution. (a) II and IV (b) I and III (c) I and II (d) III and IV 175 Consider the following statements. I. Pre-historic cave art was developed earlier than agriculture. II. Human history of growth is proportional to decline of civilisations. Select the correct option. (a) Both I and II are true (c) Both I and II are false (b) I is true, II is false (d) I is false, II is true 176 Consider the following statements. I. Fossils discovered in Ethiopia and Tanzania revealed hominid features. Reflecting that about 3-4 mya man like primates walked in Eastern Africa. II. Home erectus fossils were discovered in Java in 1891. www.mediit.in Master The NCERT > Biology (Vol-II) 178 Select the correct option. (a) I is true, II is false (c) I is false, II is true (b) Both I and II are true (d) Both I and II are false 177 Find out the incorrect statements about Homo habilis. I. Also called able or skilful man. II. Also called tool maker. III. Fossil discovered from East Africa. IV. 500 cc was its cranial capacity. V. Have teeth like modern man. VI. Lived nearly 2 million years ago. Codes A (a) 1 (b) 3 (c) 3 (d) 4 B 2 4 4 3 C 3 1 2 2 D 4 2 1 1 181 Match the following columns. Column I Column II A. Analogous organs 1. Ontogeny repeat phylogeny B. Miller and Urey 2. Experiment (chemical evolution) C. Oparin and Haldane 3. Chemical evolution (theory) The correct option is (a) IV and V (c) II, III and VI (b) Only IV (d) I, II, III, IV and VI 178 Consider the following statements. I. Australopithecus africanus had brain capacity about 500 cc similar to that of ape. II. Erect man or Homo erectus is skull was flatter than that of modern man. III. Cro-Magnon man had a slightly prognathous face. IV. Neanderthal man is regarded as most recent ancestor of today’s man. D. Human embryo have gill 4. Wings of bird and butterfly Codes A (a) 4 (b) 4 (c) 1 (d) 4 B 3 2 2 3 C 1 3 3 2 D 2 1 4 1 182 Match the following columns. Choose the incorrect statements. (a) III and IV (b) II and III (c) I and II (d) I and III A. Genetic drift 1. Change in the population’s allele frequency due to chance alone III. Matching Type Questions B. Natural selection 2. Difference in survival individuals C. Gene flow 3. Immigration or emigration changes the allele frequency D. Mutation 4. Source of the new alleles Column I (Terms) 179 Match the hominids with their correct brain size. NEET 2019 Column II Column I A. Homo habilis 1. 900 cc B. Homo neanderthalensis 2. 1350 cc C. Homo erectus 3. 650-800 cc D. Homo sapiens 4. 1400 cc Codes A (a) 3 (c) 4 Column II (Explanations) Codes A (a) 1 (c) 1 B 2 4 C 3 2 D 4 3 A (b) 1 (d) 4 C 1 1 D 4 2 A (b) 3 (d) 3 B 4 1 C 1 4 180 Match the following columns. Column I C 4 1 D 3 3 183 Match the following columns. Column I B 2 3 B 2 2 D 2 2 Column II A. Wallace 1. Natural selection B. Malthus 2. Essay of population C. Hardy-Weinberg law D. Industrial melanism 3. Biston betularia 4. p2 + 2 pq + q2 = 1 Column II A. Darwin 1. Inherited B. Genetic drift 2. Not inherited C. Mutation in germ cells 3. HMS Beagle D. Mutation in somatic cells 4. Founder effect Codes A (a) 1 (b) 1 (c) 1 (d) 2 B 2 2 3 3 C 4 3 4 4 D 3 4 2 1 www.mediit.in 179 CHAPTER 07 > Evolution 184 Match the following columns. Column I (Scientists) Column II (Related to) A. Darwin 1. Natural selection B. Lamarck 2. Inheritance of acquired character C. Pasteur 3. Swan-necked experiment D. de Vries 4. Mutational theory of inheritance Codes A (a) 2 (b) 1 (c) 1 (d) 1 B 3 3 2 2 C 4 4 3 4 Codes A (a) 3 (b) 4 (c) 2 (d) 3 D 1 2 4 3 Column I (Types of natural selection) Stabilisation selection 1. More individuals acquire value other than mean character value B. Directional selection 2. More individuals acquire mean character value C. Disruption selection 3. More individuals acquire peripheral character value at both ends of distribution curve 187 Match the Column I with Column II. Select the correct option from the codes given below. C 2 1 3 2 186 Match the following columns. Column I Mesozoic 1. First amphibians B. Devonian 2. Proliferation of reptiles C. Palaeocene 3. 160 million years D. Permian 4. Radiation of primitive mammals Codes A (a) 1 (b) 3 (c) 4 (d) 2 B 4 1 1 1 C 3 4 2 4 D 2 2 3 3 188 Match the Column I with Column II. Select the correct option from the codes given below. Primates Cranial Capacities (in cubic centimetres) A. Chimpanzee and gorilla 1. 325-510 cc B. Australopithecus 2. 500 cc C. Homo habilis 3. 700 cc D. Java ape man 4. 800-1000 cc Column II A. Ichthyosaurus 1. Caught in South Africa in 1938 B. Coelacanth 2. Fell to form coal deposits C. Giant pteridophytes 3. Disappeared about 65 mya D. Dinosaurs Column II (Related to) A. Codes (a) (b) (c) (d) D 4 3 1 1 Column II (Explanations) A. B 3 2 1 1 C 1 2 4 2 Column I (Time periods in geological time scale) 185 Match the following columns. A 1 3 2 3 B 2 1 3 4 4. Fish-like reptiles in 200 mya Codes A (a) 4 (b) 2 (c) 1 (d) 3 B 3 3 2 2 C 2 4 3 1 D 1 1 4 4 www.mediit.in Master The NCERT > Biology (Vol-II) 180 NCERT Exemplar MULTIPLE CHOICE QUESTIONS 189 The theory of spontaneous generation stated that (a) (b) (c) (d) life arose from living forms only life can arise from both living and non-living life can arise from non-living things only life arises spontaneously, neither from living nor from the non-living 190 In 1953, SL Miller created primitive earth conditions 197 Appearance of antibiotic-resistant bacteria is an example of (a) (b) (c) (d) adaptive radiation transduction pre-existing variation in the population divergent evolution 198 Match the scientists listed under Column I with ideas in the laboratory and gave experimental evidence for origin of first form of life from pre-existing non-living organic molecules. The primitive earth conditions created include listed Column II. A. Darwin 1. Abiogenesis (a) low temperature, volcanic storms, atmosphere rich in oxygen (b) low temperature, volcanic storms, reducing atmosphere (c) high temperature, volcanic storms, non-reducing atmosphere (d) high temperature, volcanic storms, reducing atmosphere containing CH4 , NH3 , etc. B. Oparin 2. Use and disuse of organs C. Lamarck 3. Continental drift theory D. Wagner 4, Evolution by natural selection 191 Palaeontological evidences for evolution refer to the (a) development of embryo (b) homologous organs (c) fossils (d) analogous organs 192 Fossils are generally found in (a) sedimentary rocks (c) metamorphic rocks (b) igneous rocks (d) any type of rock 193 The bones of forelimbs of whale, bat, cheetah and man are similar in structure, because (a) (b) (c) (d) one organism has given rise to another they share a common ancestor they perform the same function they have biochemical similarities 194 Analogous organs arise due to (a) (b) (c) (d) divergent evolution artificial selection genetic drift convergent evolution (b) Lichens (d) Lycopodium 196 Animal husbandry and plant breeding programmes (a) (b) (c) (d) reverse evolution artificial selection mutation natural selection B 4 1 4 3 C 2 2 3 2 D 3 3 1 1 199 Variations during mutations of meiotic recombinations are (a) (b) (c) (d) random and directionless random and directional random and small random, small and directional 200 ( p + q ) 2 = p 2 + 2 pq + q 2 = 1, represents an equation used in (a) (b) (c) (d) Population genetics Mendelian genetics Biometrics Molecular genetics observed in moth, Biston betularia? pollution indicator? are the examples of Codes A (a) 1 (b) 4 (c) 2 (d) 4 Column II 201 Which type of selection is industrial melanism 195 Which of the following is used as an atmospheric (a) Lepidoptera (c) Lycopersicon Column I (a) (b) (c) (d) Stabilising Directional Disruptive Artificial 202 Evolution of life shows that life forms had a trend of moving from (a) (b) (c) (d) land to water dryland to wetland freshwater to sea water water to land www.mediit.in 181 CHAPTER 07 > Evolution (c) the young ones are protected inside the mother’s body and are looked after they are born leading to more chances of survival (d) the embryo takes a long time to develop 203 Which of the following is an example for link species? (a) Lobe fish (c) Sea weed (b) Dodo bird (d) Chimpanzee 204 For the MN-blood group system, the frequencies of M and N alleles are 0.7 and 0.3, respectively. The expected frequency of MN blood group bearing organisms is likely to be (a) 42% (b) 49% (c) 9% 206 The most accepted line of descent in human evolution is NEET 2016 (a) Australopithecus → Ramapithecus → Homo sapiens → Homo habilis (b) Homo erectus → Homo habilis → Homo sapiens (c) Ramapithecus → Homo habilis → Homo sapiens (d) Australopithecus → Ramapithecus → Homo erectus → Homo habilis → Homo sapiens (d) 58% 205 Viviparity is considered to be more evolved because (a) the young ones are left on their own (b) the young ones are protected by a thick shell Answers Mastering NCERT with MCQs 1 11 21 31 41 51 61 71 81 91 101 111 121 2 12 22 32 42 52 62 72 82 92 102 112 122 (d) (d) (d) (d) (a) (a) (c) (b) (b) (a) (b) (a) (b) 3 13 23 33 43 53 63 73 83 93 103 113 123 (a) (c) (d) (b) (a) (a) (a) (a) (d) (c) (c) (b) (c) 4 14 24 34 44 54 64 74 84 94 104 114 124 (b) (a) (a) (c) (d) (c) (b) (a) (d) (b) (c) (c) (a) 5 15 25 35 45 55 65 75 85 95 105 115 125 (a) (a) (b) (c) (c) (a) (b) (a) (b) (c) (c) (d) (d) 6 16 26 36 46 56 66 76 86 96 106 116 126 (c) (a) (c) (b) (b) (d) (d) (b) (b) (a) (c) (b) (a) 7 17 27 37 47 57 67 77 87 97 107 117 127 (b) (d) (d) (b) (d) (b) (d) (c) (b) (c) (b) (c) (a) 8 18 28 38 48 58 68 78 88 98 108 118 128 (a) (a) (c) (c) (c) (d) (c) (c) (d) (b) (c) (a) (d) 9 19 29 39 49 59 69 79 89 99 109 119 (a) (b) (a) (b) (b) (b) (d) (d) (a) (d) (b) (b) 10 20 30 40 50 60 70 80 90 100 110 120 (d) (a) (b) (b) (a) (d) (b) (a) (a) (c) (c) (a) 132 142 152 162 172 182 (b) (c) (d) (c) (c) (a) 133 143 153 163 173 183 (d) (a) (b) (d) (d) (a) 134 144 154 164 174 184 (a) (d) (d) (c) (a) (c) 135 145 155 165 175 185 (a) (d) (d) (d) (a) (c) 136 146 156 166 176 186 (a) (c) (d) (c) (b) (b) 137 147 157 167 177 187 (c) (b) (d) (c) (b) (b) 138 148 158 168 178 188 (a) (d) (d) (d) (a) (c) NEET Special Types Questions 129 139 149 159 169 179 (a) (a) (a) (a) (c) (a) (d) (c) (a) (b) (c) (b) (d) (a) (d) (d) (d) (d) (b) 130 140 150 160 170 180 (b) (c) (c) (b) (b) (b) 131 141 151 161 171 181 (d) (c) (d) (a) (a) (b) NCERT Exemplar Questions 189 (c) 199 (a) 190 (d) 200 (a) 191 (c) 201 (b) 192 (a) 202 (d) 193 (b) 203 (a) 194 (d) 204 (a) 195 (b) 205 (c) 196 (b) 206 (c) 197 (c) 198 (b) www.mediit.in Master The NCERT > Biology (Vol-II) 182 Answers & Explanations 4 (b) For a long time, it was believed that life came out of 5 6 7 9 10 Answers & Explanations 17 20 decaying and rotting matter like straw mud, etc. This was the theory of spontaneous generation. Theory of spontaneous generation (abiogenesis or autogenesis) states that, life originated from non-living things in a spontaneous manner. (a) Louis Pasteur with his swan neck experiment disapproved once and for all the abiogenesis (spontaneous generation) and powered the concept of biogenesis (life originated from pre-existing one). (c) Louis Pasteur by careful experimentation demonstrated that life comes only from pre-existing life. They showed that in pre-sterilised flasks, life did not come from killed yeast, while in another flask open to air, new living organisms arose from ‘killed yeast’. (b) Oparin and Haldane proposed that the first form of life could have come from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) and that formation of life was preceded by chemical evolution, i.e. formation of diverse organic molecules from inorganic constituents. (a) Option (a) is correct. Experimentally, the chemical theory of evolution was performed by SL Miller and HC Urey in 1953. They created electric discharge in a closed flask containing CH4 , H2 , NH3 and water vapours at 800° C. They observed formation of amino acids. The ratio of methane, ammonia and hydrogen in Miller’s experiment was 2 : 1 : 2. (d) Miller added four gases methane, ammonia, hydrogen and water vapours in an air tight apparatus and passed electrical discharges from electrodes at 800°C. After a week, he found a large number of simple organic compounds including amino acids such as alanine, glycine, aspartic acid. In similar experiments, other scientists observed the formation of sugar, nitrogen bases, pigments and fats. (d) Based on observations made during a sea voyage in a sail ship called HMS Beagle round the world, Charles Darwin concluded that existing living forms share similarities to varying degrees not only among themselves but also with life forms that existed millions of years ago. There has been gradual evolution of life forms. A population has been built on variations, in characteristics. Those characteristics which enable some to survive better in natural conditions (climate, food, physical factors, etc.) would outbreed others that are less-endowed to survive under such natural conditions. (a) Alfred Wallace (1823-1913) was a British naturalist. He wrote an essay tittle ‘On the Tendencies of Varieties to Depart Indefinitely from the Original Type’. Wallace was the scientist who came to the similar conclusions around the same time of Charles Darwin. 21 (a) Malay Archipelago is a group of islands visited by 24 27 28 29 32 36 38 Alfred Wallace. It is present in South-East Asia between Australia and the Asian mainland and it separates the Indian and Pacific oceans. It includes Indonesia, the Philippines and the Malaysia. (a) Fossils are the remains of hard parts of life-forms found in rocks. These rocks form sediments and a cross-section of earth’s crust indicates the arrangement of sediments one over the other during the long history of earth. (d) Embryological support for evolution given by Ernst Haeckel includes the presence of row of vestigial gill slits in embryo of all vertebrates. This proposal was disapproved by Karl Ernst von Baer who noted that embryos never pass these gill slits to their the adult stages. He proposed that embryos start from few basic forms similarly in different animals and then develop into branching patterns. (c) The similarity of bone structure in the forelimbs of many vertebrates is an example of homology. The homologous organs have the same fundamental structure, but are adapted to perform different functions, e.g. forelimbs of man, cheetah, whale and bat. (a) Option (a) represents correct example of convergent and divergent evolution. Rest of the pairs are incorrect and the correct information is as follows Convergent evolution involves the independent development of similar structures in organisms that are not directly related. It is represented by analogous organs, e.g. eyes of Octopus and mammals, wings of insects and birds. In divergent evolution, same basic organs are adapted by organisms to perform different and specialised functions. It is represented by homologous organs, e.g. forelimbs of vertebrates (like seal’s flipper, bat’s wing, cat’s paw, horse’s front leg and human hand), thorns of Bougainvillea and tendrils of Cucurbita. (d) Eyes of Octopus, bat and man are examples of analogous organs which show convergent evolution. Therefore, option (d) is incorrect. Divergent evolution results in homologous structures. These organs have the same fundamental structure but are different in functions. Structural homology is seen in brain, heart and forelimbs of man, bat and cheetah. (b) The given diagram indicates homologous organs. Whales, bats, cheetah and human (all mammals) share similarities in the pattern of bones of forelimbs. In plants, the thorns and tendrils of Bougainvillea and Cucurbita, respectively represent homology. (c) The analogous organs are not anatomically similar structures but these perform similar functions. Hence, analogous structures are a result of convergent evolution, i.e. different structures evolving for the same functions and hence, show similarity. www.mediit.in 183 CHAPTER 07 > Evolution 41 42 44 45 46 48 49 53 54 60 61 (d) In Australia, marsupials and placental mammals 62 63 64 65 68 69 70 72 80 have evolved to share many similar characteristics. This type of evolution is referred to as convergent evolution. Convergent evolution is the independent evolution of similar features in species of different lineages. For example, a number of marsupials, each different from the other evolved from an ancestral stock, but all within the Australian Island continent. Also, marsupials in Australia resemble placental mammals in the rest of the world, they evolved in isolation after Australia separated from other continents. (c) Option (c) is correct. Adaptive radiation occurs when a population of a species invades a new area. It is because it provides the organisms of the population a new habitat with plenty of niche spaces. Darwin’s finches represent one of the best examples of this phenomenon. (a) Darwin’s fitness is related to and organism’s ability to survive and reproduce better than the other members of the species under abnormal environmental conditions. (b) The organisms, which acquire or develop favourable variations would survive because they are fittest to face their surrounding, while unfit organisms are eliminated. (b) Darwinian fitness can be estimated by the number of offspring produced by different individuals in a population. The organisms which bear favourable variations in accordance to the environment have more offspring than the others which do not have variations in accordance with environment. (c) Sexual selection is an example of natural selection as it is the type of natural selection in which one sex is preferred for certain characteristics by the individuals of other sex. Natural selection involves the selection of those animals which are better adapted to an environment for reproduction and growth (survival). (d) Reproduction by sexual methods brings about changes in genes of progeny. In genes of sexually reproduced organisms, independent assortment of genes and genetic recombination takes place. Due to these events, the progeny have high rate of natural selection than the asexually repoducing organisms. (b) Darwin stated that the organic evolution is due to the interspecific competition. It is the competition between members of different species. Intraspecific competition occurs amongst members of the same species for obtaining optimum amounts of their food, shelter, mate, water, light, etc. (b) Natural selection theory of Darwin did not believe in any role of discontinuous variation. Darwin called these variations as sports, while Hugo de Vries used the term mutation for these variations. These variations are sudden heritable changes, which can occur in any stage of development. (a) Hugo de Vries proposed that the variations caused by mutation are random and directionless. These are the sudden, heritable changes in the genetic material and these variations constitute the raw material for Answers & Explanations 39 The eyes of Octopus and eyes of cat are examples of analogous organs. That have evolved due to the convergent evolution. (b) Convergent evolution refers to independent evolution of similar features in species of different periods in time. These features evolve in response to common environmental abnormalities. Thus, option (b) is correct. (c) Biochemical similarities are based on the study of similarities in protein and genes of organisms. These biochemical similarities point towards same shared ancestry as structural similarities among diverse organisms. (a) Change of lighter coloured variety of peppered moths (Biston betularia) to darker variety in the industrial area occurred due to the selection of darker variety for survival. It is an excellent example which supports the theory of natural selection by Charles Darwin. (d) Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the black soot (smoke) covered surroundings. Before industrialisation, all moths were white and were unnoticed from predatory birds. After industrialisation, white moths were more evidently visible and thus, picked up by birds. But black moths escaped unnoticed, so they managed to survive resulting in more population of black moths and less population of white moths. (c) Lichens are very sensitive to air pollution specially to gas sulphur dioxide. Lichens are the symbiotic association of algae and fungi. Generally, lichens are not found in polluted industrial areas. (b) Industrial melanism is the term used to describe the evolutionary process in which darker moths came to be predominate over the lighter moths, since the industrial revolution in England in 1850s as a result of natural selection. (c) Evolution is not a direct process and is based on chance events and chance mutations in organisms. Thus, it is a discontinuous and stochastic process. (b) Development of different functional structures from a common ancestral form is called adaptive radiation. The concept of adaptive radiation in evolution was developed by HF Osborn in 1902. Homologous organs show adaptive radiation. (a) The diversity in the type of finches and adaptation to different feeding habits on the Galapagos islands was observed by Darwin. He provides an evidence of origin of species by natural selection. (c) Darwin explained that adaptive radiation gave rise to the varieties of marsupials (pouched mammals) in Australia by the same process of adaptive radiation as found in the finches of Galapagos Islands. (d) Lemur and spotted cuscus are not examples of adaptive radiation. These are examples of convergent evolution. Rest of the pairs are examples of adaptive radiation. www.mediit.in Master The NCERT > Biology (Vol-II) 184 evolution. He also proposed that mutations play a key role in speciation and used the term saltation for single step large mutations. 81 (a) Hardy-Weinberg principle is applicable for allelic frequency of non-evolving population under stable conditions. 82 (b) Hardy-Weinberg principle states that allele frequencies remains constant from generation to generation. This is called as genetic equilibrium. 85 (b) The frequency of homozygous dominant, heterozygous and homozygous recessive individuals would be 0.16 (AA); 0.48 (Aa); 0.36 (aa). The frequencies are calculated as follows Frequency of dominant allele (p) = 0.4 (given) Frequency of recessive allele (q) = 1 − 0.4 = 0.6 Frequency of homozygous dominant individuals (AA) = p 2 = (0.4)2 = 0.16 Frequency of heterozygous individual (Aa)= 2 pq = 2 ( 0.4 ) ( 0.6 ) = 0.48 Frequency of homozygous recessive individual (aa) = q 2 = ( 0.6 )2 = 0.36 87 (b) Hardy-Weinberg principle states that the allele frequencies in a population are stable and remain constant from generation to generation. This can be expressed by the equation p 2 + 2 pq + q 2 = 1 or ( p + q )2 = 1 88 Answers & Explanations 89 90 93 where, p 2 represents frequency of homozygous dominant genotype, 2 pq represents the frequency of heterozygous genotype and q 2 represents the frequency of homozygous recessive genotype. Hence, option (b) is correct. (d) The tendency of population to remain in genetic equilibrium may be disturbed by lack of random mating. When in a population allele or gene frequencies remain same over generations, the population is said to be non-evolving and in genetic equilibrium. This equilibrium is disturbed by following factors, i.e. mutation, gene flow, geneic drift, natural selection and no random mating. (a) Sometimes the change in allele frequency is so different in the new sample of population that they become a different species. The original drifted population becomes the founder of new population and the effect is called founder effect. (a) Genetic drift is a drastic change in allele frequency when population size is very small. Its effects are more marked in a small isolated population. (c) Option (c) represents the correct labellings and the description is as follows l Stabilising selection (Balancing selection) This type of selection favours average sized individuals, while eliminates small sized individuals. It reduces variation and hence, does not promote evolutionary changes. Hence, it is given by Type I graph l l Directional selection (Progressive selection) In this selection, the population changes towards one particular direction. It means this type of selection favours small or large-sized individuals and more individuals of that type will be present in new generation. The mean size of the population changes. Hence, it is given by Type II graph. Disruptive selection (Diversifying selection) This type of selection favours both small-sized and large-sized individuals. It eliminates most of the members with mean expression, so as to produce two peaks in the distribution of the trait that may lead to the development of two different populations. This kind of selection is opposite of stabilising selection and is rare nature but is very important in bringing about evolutionary changes. Hence, it is given by Type III graph. 94 (b) Directional selection leads to change in the phenotypic characters of a population in one direction. In the case of artificial selection to obtain high milk yielding cows, it is intentionally done to increase the milk production, hence, it is directional. This is because only high milk yielding cows are produced. 95 (c) Option (c) is correct. Albinism is an autosomal recessive genetic disorder. It is given that frequency of an albino in a population is 1 in 10,000, i.e. 0.0001. According to Hardy-Weinberg law p 2 + q 2 + 2 pq = 1 Now, q 2 = 0.0001 q = 0.0001 = 0.01 96 97 99 103 105 Also, p + q = 1 So, p = 0.99 Hence, 2 pq = 2 × 0.01 × 0.99 = 0.02 or 2% Accordingly, 2 individuals in 10000 will be carriers of albinism. (a) Allopatric speciation occurs when genetically related populations inhabit widely separated geographical area. The population becomes entirely separated and finally constitutes a new species. Formation of Darwin’s finches that formed separate species in Galapagos islands is an example of allopatric speciation. (c) The pair in option (c) is incorrect and can be corrected as follows. First organisms that invaded land were supposed to be plants and not single-celled animals. Rest of the pairs are correct. (d) Azoic means no life. It was the era which prevailed during the origin of earth. At that time, there was no hostile conditions for the survival of any living organisms. (c) Cenozoic era is also called the age of mammals. In this era, the first mammals originated on earth. (c) Archaeopteryx (Archlae –primitive; pteryx – wing ) is an extinct animal. It was found in the rocks of Jurassic period. It was discovered by Andreas Wagnar in 1861. It displayed the characters of both reptiles and birds. www.mediit.in 185 CHAPTER 07 > Evolution 129 (a) Both Assertion and Reason are true and Reason is Its corrected form is as follows Tyrannosaurus rex was the biggest land reptile which was about 20 feet in height and had huge dagger-like teeth. Fish like reptile was Ichthyosaurus. Rest of the pairs are correctly matched. 113 (b) In the quaternary period there were two epochs l l Holocene including only modern humans. Pleiostocene including ice age and various human species. 130 115 (d) Option (d) represents the incorrectly matched pair. It can be corrected as Two mya Australopithecus probably lived in East African grasslands. Evidences show that they hunted with stone weapons but essentially ate fruits. Rest of the pairs are correct. 119 (b) Neanderthal man with a brain size of 1400 cc lived in near East and Central Asia, Europe and North Africa between 10,00,00 to 40,000 years back. It had slightly prognathus face, sloping forehead, eyebrow ridges, smaller or no chin, large receding jaws, thick-boned skull and high domed head. 120 (a) Homo erectus (Erect man) appeared about 1.7 million years ago in middle Pleiostocene. Homo erectus was evolved from Homo habilis. He was about 1.5-1.8 metres tall. He was the progenitor of two main sub species Neanderthal and Cro-Magnon man. 122 (b) Cro-Magnon man or Homo sapiens fossilis was more intelligent than modern man. They were cave dwellers having prominent chin and appeared after Neanderthal man. The cranial capacity of Cro-Magnon man was 1650 cm 3 and that of living modern man is 1450 cm 3 . 123 (c) The most significant trend in the evolution of modern man is the increased brain capacity from the ancestors. The first human being was the hominid, called Homo habilis. Their brain capacity was between 650-800 cc. 126 (a) Homo sapiens arose in Africa and moved across continents and developed into distinct races. During the ice age between 75,000-10,000 years ago modern Homo sapiens arose. Pre-historic cave art developed about 18,000 years ago. One such cave paintings by Pre-historic humans can be seen at Bhimbetka rock shelter in Raisen district of Madhya Pradesh. Agriculture came around 10,000 years back and human settlements started. 127 (a) The chronological order of human evolution is as follows Ramapithecus (earliest hominid fossil about 14-15 mya) ↓ Australopithecus (first ape man about 2 mya) ↓ Homo habilis (tool maker handyman about 1.2-1.5 mya) ↓ Homo erectus (Erect man about 1.5 mya) 131 132 133 134 135 the correct explanation of Assertion. Theory of chemical evolution states that life originated from pre-existing non-living organic molecules and the formation of life was preceded by chemical evolution. The conditions on primitive earth which favoured chemical evolution were high temperature (4800°C), volcanic storms and a reducing atmosphere that contained CH4 , NH3 , water vapours, etc. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The theory of special creation states that God created life by his divine act of creation. This theory lacked scientific evidences and thus was not accepted. Theory of spontaneous generation states that life originated from decaying and rotting matter like straw, mud, etc. Louis Pasteur rejected the theory of spontaneous generation and demonstrated that life came from pre-existing life froms. (d) Assertion is false, but Reason is true. Assertion can be corrected as Earth is about 4.5 billion years old. Primitive earth had no atmosphere and contained water vapours, CH4 , CO2 , NH3 . Life appeared 500 million years back after the formation of earth. (b) Both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion. Primitive earth was devoid of oxygen and hence, only those organisms which were able to survive in anaerobic condition developed. All those organisms were heterotrophic. Later, after autotrophic organisms developed, which used inorganic sources such as H2 S, NH3 , CH4 as source of energy. These organisms were called chemoautotrophs. (d) Assertion is false, but Reason is true. Assertion can be corrected as Coacervates were aggregates of organic biomolecules surrounded by film of water molecules. These lacked definite membrane, but did exhibit some life like characters. Microspheres were non-living collections of organic macromolecules, double-layered and formed from proteinoids, by heating a mixture of amino acids at 180°C. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Ernst Haeckel supported the embryological similarities as an evidence of evolution. He gave the biogenetic law, ‘Ontogeny recapitulates phylogeny’ which states that an organism repeats its ancestral history during its development. The embryos of all vertebrates including humans develop a row of vestigial gill slits which degenerate and are absent in adult vertebrates. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Darwin believed that the small and useful variations make some species more adapted to the changing environment than others. Answers & Explanations 111 (b) Option (b) represents the incorrectly matched pair. www.mediit.in Master The NCERT > Biology (Vol-II) 186 136 137 138 139 140 141 Answers & Explanations 142 143 146 Out of heterogeneous population, nature selects the best adaptative individuals, while less fit or unfit individuals are rejected because they fail to survive and reproduce. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Whales and mammals share similarities the pattern of bones of forelimbs because these organs are homologous organs and suggest occurrence of divergent evolution. Homologous organs follow the basic plan of organisation during development, but in adult stage, they modified to perform different functions as an adaptation to different environments. (c) Assertion is true, but Reason is false and it can be corrected as Divergent evolution gives rise to homology. Analogy arises due to convergent evolution. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Lichens are good pollution indicators. These do not grow in areas that are polluted because these organisms are sensitive to SO 2 gas present in polluted areas up to great concentration. (d) Assertion is false, but Reason is true. Assertion can be corrected as Lichens are the symbiotic relationship of algae and fungi. These are good pollution indicators because these are sensitive to SO2 levels in air. (c) Assertion is true, but Reason is false and can be corrected as Mutations are sudden changes which bring sudden variations in organism. (c) Assertion is true, but Reason is false and can be corrected as If the gene migration happens multiple times, it is called gene flow. Gene recombination occurs due to the independent assortment of chromsomes, crossing over during meiosis, random fusion of gametes and the formation of new alleles. (c) Assertion is true, but Reason is false and can be corrected as Mutations lead to speciation and hence, Lamarck called it saltation and proposed Lamarckism. Lamarckism was rejected by August Weismann who proposed the theory of continuity of germplasm. Sudden inheritable changes take place in genome of an organism due to certain factors called mutations. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Among the primates, chimpanzee is the closest relative of the present day humans. This is because the banding pattern in the autosome number 3 and 6 of man and chimpanzee is remarkably similar. (c) The statement in option (c) is true regarding the theory of natural selection. Other statements are incorrect and can be corrected as l Lamarckism is the first theory of organic evolution. l l Palaeontology explains the information derived from fossils. Modern synthetic theory of evolution explained the concept of speciation. 147 (b) The statement in option (b) is incorrect for Darwinism. It can be corrected as Mutations are random and directionless, while Darwinian variations are small and directional. Evolution according to Darwin was a gradual process. Rest of the statements are correct. 152 (d) Statement IV stands in favour of abiogenesis which states that life originated from non-living matter. Other statements are incorrect for biogenesis as these statements support the theory of biogenesis. 153 (b) Statements I and V are correct representation of homologous organs. Hands of man and wings of bat, as well as forearm of humans and forelimbs of horses are the examples of homology because these have same or common origin (i.e. similarity in pattern of bones), but have different functions. Rest of the statements are incorrect and can be corrected as Wings of cockroach and wings of bats as well as wings of birds and wings of butterfly are analogous organs. 154 (d) Statements II, III and IV are correct whereas I is incorrect. Its correct form is as follows Wings of insects and birds are analogous organs because they perform the same function, but have different origins. 155 (d) Statements II and III are incorrect and their corrected forms are as follows l l Natural selection includes variation. Theory of natural selection was given by Charles Darwin. This theory states that the variations which are favourable to environment and inheritable are the major cause of evolution. Rest of the statements, i.e. statement I, IV and V are correct. 156 (d) Statements I, II, III, IV and VI are correct, while statement V is incorrect. Its corrected form is as follows Genetic drift is the random change in the frequency of alleles in a population over successive generation due to the sampling error in gametes. It operates in small populations. 157 (d) Statements I, II and III are true for genetic drift. Statement IV is incorrect and can be corrected as Migration rather than mutation is primary responsible for genetic drift as it operates in small populations. 159 (d) Statements I, II and IV. But statement III is incorrect and can be corrected as Theory of acquired character was given by Lamarck (also called Lamarckism). Mutational theory of evolution was given by Hugo de Vries which states that sudden inheritable change is the cause of evolution. www.mediit.in 187 CHAPTER 07 > Evolution corrected as l l Evolution is always considered as the appearance of characters should also be transmitted to the offspring otherwise the changes are lost. Adaptive ability cannot be considered as evolution because this ability may be temporary due to the environmental changes. Rest of the statements are correct. 161 (a) Statement I and II are correct conditions to determine that two species are different. This can be explained as Species are a group of interbreeding individuals producing fertile offsprings. If two individuals fails to follow this criteria they belongs to different species. But members of a species can have different body colour and appear morphologically slightly different. Therefore, these criterias do not justify that two individuals are of different species. 162 (c) Statements III and IV are correct for organic evolution, while statements I and II are incorrect. It can be corrected as l l 177 (b) Statement IV is incorrect about Homo habilis. It can be corrected as Homo habilis had about 700 cc cranial capacity. Ape man had about 500 cc cranial capacity. Rest of the statements are correct. 178 (a) Statements III and IV are incorrect and can be corrected as l l 189 (c) The theory of spontaneous generation stated that 190 Homologous structures have the same embryonic origin and basic structure, but they do not perform same function, e.g. flipper of whale and wings of bat. Analogous organs are the structures which are different in their basic structure and developmental origin, e.g. wings of butterfly and wings of bird. 167 (c) Statements I and IV are correct. 168 169 172 174 Mendel’s laws of inheritance and Weismann’s theory of continuity of germplasm (1892) discarded Lamarck’s concept of inheritance of acquired characters. These two concepts gave the insight of inheritance pattern in organisms and the mechanism inovled in it. (d) According to modern theory of evolution, the five factors involved in the process of organic evolution are as mutations, genetic drift, gene migration (gene flow), gene recombination and hybridisation. Thus, statements I, II and III support the modern theory of evolution. (d) Statements I, II, IV and V are correct and statement III is incorrect. It can be corrected as Genetic drift is the random change in the allele frequency caused by sampling error across generation in a definite population. The consequences of genetic drift are not predicted that is why it is called non-directional. (c) Statements II and III are correct for natural selection. Statement I is incorrect and it can be corrected as Natural selection tends to increase the characters that inturn increases the chances of survival and reproduction of an organism. (a) Statements II and IV are correct. Statements I and III are incorrect and can be corrected as l l Gene mutations are random changes in the bases of sequences of genes. Genetic drift is also called Sewall Wright effect. Neanderthal man had a slightly prognathous face (having a forward projecting face and jaws). Cro-Magnon man is regarded as most recent ancestor of today’s man. Rest of the statements are correct. 191 192 193 194 life can arise from non-living things only. It is also known as the theory of abiogenesis. Louis Pasteur by careful experimentation disapproved this theory and demonstrated that life arose from living forms (pre-existing life). (d) The primitive earth conditions include high temperature, volcanic storms and reducing environment containing methane ( CH4 ), ammonia ( NH3 ), hydrogen ( H2 ) and water ( H2 O ). The Miller-Urey experiment tested for the occurrence of chemical evolution by stimulating hypothetical conditions present on early earth. They ultimately found that a large number of simple organic compounds including some amino acids such as alanine, glycine and aspartic acid can be synthesised as during chemical origin of life. (c) Palaeontological evidences for evolution refer to the evidences obtained from fossils. Fossils are the preserved remains or traces of organisms from the distant past. The study of fossils is called Palaeontology. Homologous and analogous organs provide evidences for comparative anatomy and morphology. (a) Fossils are generally found in sedimentary rocks, which are formed by the gradual deposition of silt, sand or calcium carbonate over millions of years in regions such as lakes or sea. During their formation, the dead animals are carried to the sea or large lake, sink down and get burried in the rocks. The animals, thus preserved in the rocks, are converted into fossils. (b) The bones of forelimbs of whale, bat, cheetah and man are similar in structure, because they have a common ancestor. These are homologous organs which have different functions across diverse forms, but are developed along the same pattern. These organs arise due to divergent evolution. (d) Analogous organs arise due to the convergent evolution. These organs have similar functions, but are different in their structural details and origin, e.g. wings of insect and bird. Answers & Explanations 160 (b) Statements II and III are incorrect and can be www.mediit.in Master The NCERT > Biology (Vol-II) 188 201 (b) Directional selection is observed in the moth, Biston indicator. These do not grow in areas that are polluted, as they are sensitive (especially phycobiont) to oxides of nitrogen and sulphur hence, unable to synthesise organic food and do not grow well. 197 (c) Appearance of antibiotic-resistant bacteria is an example of pre-existing variation in the population. When a bacterial population encounters a particular antibiotic, those sensitive to it die. But some bacteria having mutations become resistant to the antibiotic. Soon, the resistance providing genes become widespread and the entire population becomes resistant to that particular antibiotic. 199 (a) Variations during mutations of meiotic recombinations are random and directionless. Hugo de Vries based on his work on evening primrose stated that it is mutation, which causes sudden appearance of variations that results in speciation. He stated that mutations are sudden, heritable and persistant in successive generation. He contradicted Darwinian variations which are stated as small and directional. 200 (a) (p + q) 2 = p 2 + 2 pq + q 2 = 1represents an equation used in population genetics. It is the mathematical representation of ‘Hardy-Weinberg principle’. This principle says that allele frequencies in a population are stable and is constant from generation to generation, i.e. the gene pool remains a constant. betularia during industrial melanism. Under this, individuals at one end of the frequency distribution are favoured and so more individuals of that type will be present in the next generation. 202 (d) Evolution of life shows that life forms had a trend of moving from water to land. The early vertebrates were fishes (which lived in only water). Some fishes gradually changed into amphibians (can live both on land and in water). Certain amphibians then transformed into the reptiles (live on land) some of the later finally evolved into birds (can fly) and than mammals. Thus, showing that life forms moved from water to land. 204 (a) The expected frequency of MN-blood group bearing organisms is likely to be 42%. If the frequencies of M and N alleles are 0.7 and 0.3, respectively, the frequency of MN-blood group can be calculated as follows Frequency of MN-blood group = 2 pq = 2 × 0.7 × 0.3 = 0. 42 or 42% 205 (c) Viviparity is considered to be more evolved because the youngs ones are protected inside the mother’s body and are looked after once they are born, leading to more chances of survival, e.g. mammals. However, in oviparity, the female lays fertilised / unfertilised eggs covered by a hard calcareous shell in a safe place in the environment. The chances of survival are less as the young ones are left on their own. Answers & Explanations 195 (b) Lichens can be used as an atmospheric pollution www.mediit.in CHAPTER > 08 Human Health and Diseases NEET Å Health is a state of complete physical, mental and social well-being rather than only physical fitness or the absence of disease. n n Å Å KEY NOTES Health is affected by genetic disorders, infections and life style. Balanced diet, personal hygiene, regular exercise, rest and thinking are very important to maintain good physical and mental health. Awareness about diseases and their effect on different body functions, vaccination against infectious diseases, proper disposal of wastes, control of vectors, maintenance of hygienic food and water resources all are necessary for health. Disease is the condition of improper functioning or any condition which interferes with the normal functioning of one or more organs of the body and causes disorder of mind or body. It is characterised by various signs and symptoms. Diseases can be broadly classified into n n Congenital diseases These diseases are present in human since birth (genetic disorders) or are caused due to mutation, e.g. Down‘s syndrome, sickle-cell anaemia, etc. Acquired diseases These diseases develop after birth and are not transferred from parents to offspring. These diseases are further categorised into n n Infectious diseases or Communicable diseases These diseases are easily transmitted from a diseased person to a healthy person. The infectious diseases are very common, e.g. AIDS, common cold, etc. Non-infectious diseases or Non-communicable diseases These diseases cannot be transmitted from a diseased person to a healthy person. These diseases are caused by agents other than pathogens, e.g. cancer, diabetes, etc. Common Diseases in Humans Å Pathogen is an organism which can cause disease in human. These can belong to bacteria, viruses, fungi, protozoans, helminths, etc. Å Most parasites are therefore pathogens as these cause harm to the host by inhabiting them. Å The pathogens can enter our body by various means, multiply and interfere with normal vital activities and cause morphological and functional damage. Å Pathogens have to adapt to life within the environment of the host, e.g. the pathogens that enter the gut must know a way of surviving in the stomach at low pH and resisting the various digestive enzymes. Å Vectors, on the other hand, do not cause disease themselves, but act as carriers to transmit the pathogen from an infected person to a healthy person, i.e. spread the disease, e.g. famale Anopheles mosquito. Å Some common diseases and their pathogenic members are discussed as follows Bacterial Diseases Some common bacterial diseases are as follows 1. Typhoid is caused by a bacterium called Salmonella typhi. Å S. typhi enters the small intestine through contaminated food and water and migrate to other organs through food and blood. Å Symptoms are high fever (39-40°C), weakness, stomach pain, constipation, headache and loss of appetite. Intestinal perforation and in severe cases death may occur. Å Widal test is the confirmatiory test for diagnosis of typhoid. www.mediit.in Master The NCERT > Biology (Vol-II ) 190 2. Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae. Å These bacteria infect alveoli of the lungs. The alveoli get filled with a fluid which causes decrease of respiratory efficiency of the lungs. Å Pneumonia spreads by inhaling droplets/aerosol from infected individuals, sharing glasses and utensils with an infected person. Å Symptoms of pneumonia are fever, chills, cough, headache, etc. In severe cases, the lips and finger nails may turn grey bluish in colour. 3. Plague is caused by Pasteurella/Yersinia pestis and is also called black death. 4. Diphtheria is caused by Corynebacterium diphtheriae and is characterised by difficulty in breathing due to infection in the mucous membrane of upper respiratory tract. Å When the mosquito bites another human, sporozoites are injected with bite. Mature infective stages (sporozoites) escape from gut and migrate to the mosquito salivary glands. Sporozoites Salivary glands Mosquito Host Fertilisation and development take place in the mosquito’s gut. s yte Female toc e m mosquito Ga takes up Female gametocytes with blood Male meal. Common cold occurs due to a group of viruses called rhino viruses. Å These viruses infect the nose and the respiratory passage, but not the lungs. Å Symptoms include nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., which generally last for 3-7 days. Å The infection occurs when droplets from cough or sneeze of an infected person are either inhaled directly or transmitted through contaminated objects such as pen, books, cups, computer’s keyboard or mouse, etc. Parasites (sporozoites) reach the liver through blood. Human Host Sexual stages (gametocytes) develop in red blood cells. Viral Diseases Å Life cycle of Plasmodium is given in the figure below Å Thus, malarial parasite requires two hosts to complete its life cycle, i.e. human and mosquito. 2. Amoebiasis (amoebic dysentery) is caused by an intestinal endoparasite, Entamoeba histolytica, which is a protozoan parasite of the large intestine of humans. Å Carrier of pathogens is housefly. It transmits the parasite from faeces of an infected person to the food. Å Infection takes place through the contaminated food and water. Å Symptoms are abdominal pain, constipation, cramps, faeces with excess mucus and blood clots. Helminthic Diseases Some common protozoan diseases are as follows Some common helminthic diseases are as follows NEET Parasites reproduce asexually in red blood cells, then bursting them and release haemozoin toxin which causes cycles of fever and other symptoms. Released parasites infect new red blood cells. Stages in the life cycle of Plasmodium Protozoan Diseases 1. Malaria is caused by different species of the protozoan Plasmodium (vivax, malariae and falciparum). Å P. falciparum causes most serious kind of malaria which can be fatal. Å Female Anopheles mosquito is the vector of Plasmodium which transfers the sporozoites (infectious form). The parasite reproduces asexually in liver cells, bursting the cell and releasing into the blood. 1. Ascariasis is caused by an intestinal endoparasite of human, Ascaris lumbricoides commonly called as roundworm. Å Infection occurs as the eggs of parasite excreted along with faeces of infected person, contaminate water and soil. Å Å Infection reaches human beings through contaminated vegetables, fruits and water. Symptoms of disease are abdominal pain, indigestion, muscular pain, fever, anaemia, nausea, headache and the blockage of intestinal passage. KEY NOTES www.mediit.in 191 CHAPTER 08 > Human Health and Diseases 2. Filariasis/Elephantiasis is caused by filarial worms Wuchereria bancrofti and Wuchereria malayi. Å Culex mosquito (female) is the vector. Å Symptoms are chronic inflammation of organs in which they live, blockage of lymph vessels of lower limbs resulting in swelling. Å Genital organs also get affected leading to their deformation. 1. Innate Immunity It is present from birth and is inherited from the parents. It is non-specific and consists of following four types of barriers Å Physical barriers prevent entry of microorganisms in the body. For example, skin, mucus coating of epithelium lining of respiratory, gastrointestinal and urogenital tracts. Å Physiological barriers prevent microbial growth in the body. For example, acid in the stomach, saliva in the mouth, tears from eyes. Å Cellular barriers phagocytose and destroy microbes. For example, some WBCs like Polymorpho-Nuclear Leucocytes (PMNL- neutrophils) and monocytes and natural killer cells (type of lymphocytes) in the blood as well as macrophages in tissues. Å Cytokine barriers Virus-infected cells secrete proteins called interferons, which protect non-infected cells from further viral infection. Fungal Diseases Ringworm is caused by fungi of the genera–Microsporum, Trichophyton and Epidermophyton. Å Infection occurs through contact with an infected person or from soil, through the use of towels, clothes, combs, etc., of an infected person. Å Symptoms of ringworm are appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp accompanied by intense itching. Å Heat and moisture help these fungi to grow in regions like folds as in groin or between the toes. 2. Acquired Immunity Å The immunity acquired after birth is called acquired immunity. Å Acquired immunity is pathogen specific. Å It is characterised by memory. This means when our body encounters a pathogen for the first time it produces a response called primary response which is of low intensity. Å Subsequent encounter with the same pathogen elicits a highly intensified secondary or anamnestic response. This is ascribed to the fact that our body appears to have memory of the first encounter. Å The primary and secondary immune responses are carried out with the help of two special types of lymphocytes present in our blood, i.e. B-lymphocytes and T-lymphocytes. Å The B-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies. Å The T-cells themselves do not secrete antibodies but help the B-cells to produce them. Immunity Å The acquired immunity may be active or passive. It is the ability of the body (host) to fight against disease causing agents. Immunity is of two types. Å Active immunity is generated by the body on exposure to antigen. Active immunity can also be achieved through vaccination, e.g. polio vaccine, tetanus vaccine, etc., (artificially acquired). On the basis of action of responding cell, active immunity is of two types Prevention and Control of Infectious Diseases Å Å Maintenance of personal and public hygiene is very important for prevention and control of many infectious diseases. Personal hygiene includes keeping the body clean, consumption of clean drinking water, food, etc. Public hygiene includes proper disposal of waste and excreta, periodic cleaning of water reservoirs, etc. Other preventive measures include n n n n n Eradication of vectors and destroying their breeding sites. Use of mosquito nets and repellants. Introducing fishes like Gambusia in pond that feed on mosquito larva. Vaccination and immunisation programmes for diseases. Use of antibiotics and other drugs can significantly and effectively treat infectious diseases. Immunity Innate immunity (inborn immunity) Acquired immunity (adaptive immunity) Active immunity Passive immunity n Cell-mediated immunity This immunity is due to T-lymphocytes, which mature in thymus. The graft rejection during organ transplantation is due to the ability of the T-cells to differentiate between self and non-self is cell-mediated immunity. NEET KEY NOTES www.mediit.in Master The NCERT > Biology (Vol-II ) 192 n Å Humoral immunity This is due to B-lymphocytes, which secrete specific antibody when exposed to a particular antigen. These antibodies flow into the body fluids and neutralise the antigen. Passive immunity develops due to direct transfer of actively formed antibodies. For example, the yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant. The foetus also receives some antibodies from their mother, through the placenta during pregnancy. Å Allergy Å It is the exaggerated response of the immune system to certain antigens present in the environment known as allergens. Å These can be pollen grains, animal dander, dust, feathers, penicillin drugs, etc. Antibodies Å Å Å n These are the proteins (immunoglobulin) produced within the body by the plasma cells against antigens. n The basic structure of all antibody/ Immunoglobulin (Ig) molecule consists of four polypeptide chains linked by disulphide bonds. Two small chains called light chain and two longer chains called heavy chain are present. Five different types of immunoglobulins are known and these are as follows Antibody Description IgG Most prevalent class of antibody, 75-80% of total antibody. It can cross placenta from mother to child and confer immune protection to newborns. IgM They are the first to be produced in response to encounter with a pathogen. Responsible for blood transfusion reactions in ABO blood system. IgA Found in colostrum, i.e. breast milk for newborns to provide passive immune protection. IgE It is involved in allergic reactions. IgD It resembles IgG structurally and serves as a recognition receptor for antigen. It activates and suppresses lymphocyte activity. Vaccination and Immunisation Å The process of introduction of inactivated or weakned pathogen into the body to provide protection against a disease is called vaccination. Å Immunisation is the process by which the body produces antibodies against the vaccine (primary response) and develops the ability to neutralise pathogens during actual infection in the body (secondary response). Å Vaccine generates B and T-cells that recognise the pathogens on subsequent exposure and produce an intense immune response. Å In case of requirement of quick immune response like tetanus or snake bite infection, pre-formed antibodies or antitoxin (a preparation containing antibodies to the toxin) are injected into the patient. This is called passive immunisation. NEET Recombinant DNA technology has produced antigenic polypeptides of pathogen in bacteria or yeast. This allowed large scale production of vaccines, e.g. hepatitis-B vaccine from yeast. n n IgE antibodies are produced in response to allergens. Causes of allergy are histamine and serotonin released from the mast cells. Symptoms of allergy are sneezing, watery eyes, running nose, difficulty in breathing. Treatment of allergy include doses of antihistamine, adrenaline and steroids. Autoimmunity Å Higher vertebrates’ immune system can distinguish foreign molecules as well as foreign organisms and mount a response to destroy them. Å But sometimes, due to genetic and other unknown reasons, the body attacks self cells. This results in damage to the body this is called autoimmunity and the disease is called auto-immune disease. Å Rheumatoid arthritis which affects many people in our society, myasthenia gravis, etc. are some examples of auto-immune diseases. Immune System in the Body Å The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies. Å The immune system also plays an important role in allergic reactions, auto-immune diseases and organ transplantation. Lymphoid Organs Å These are the organs where origin and/or maturation and proliferation of lymphocytes occur. The primary lymphoid organs are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes. Å After maturation, the lymphocytes migrate to secondary lymphoid organs like spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix. The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells. KEY NOTES www.mediit.in 193 CHAPTER 08 > Human Health and Diseases Å The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. Å Both bone marrow and thymus provide micro-environments for the development and maturation of T-lymphocytes. Å The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. It acts as a filter of blood by trapping blood-borne microorganisms. It is also called the graveyard of RBCs. Å The lymph nodes are small solid structures located at different points along the lymphatic system. Lymph nodes serve to trap microorganisms or other antigens, which happen to get into the lymph and tissue fluid. Å A lymphoid tissue is also located within the lining of the major tracts (respiratory, digestive and urogenital tracts) called Mucosal Associated Lymphoid Tissue (MALT). It consititutes about 50 per cent of the lymphoid tissue in the human body. AIDS Å It refers to the deficiency of the immune system, acquired during the life-time of an individual, indicating that it is not a congenital disease. It was first reported in 1981 in USA. Å The causative agent is Human Immunodeficiency Virus (HIV). It belongs to the group of viruses called retro virus. It has single-stranded RNA genome enclosed in an envelope. Å These virus particles enter helper T-lymphocytes (TH cells) in the blood, where they continue to replicate and produce viral progeny. Å The number of helper T-lymphocytes progressively decreases in the body of the infected people. Å As the number of T-cells decrease, immunity also decreases. As a result, the person cannot produce any immune response even against common bacteria like Mycobacterium, parasites like Toxoplasma viruses and fungi. During this period, person suffers from fever, diarrhoea and weight loss. Treatment and Diagnosis Å Å Enzyme Linked Immuno-Sorbent Assay (ELISA) is used as a diagnostic test for AIDS. Treatment of AIDS with anti-retroviral drugs is only partially effective. These can only prolong the life of the patient, but cannot prevent death. Prevention of AIDS Å As AIDS has no cure, prevention is the best option. Preventive measures for HIV infection are n Å HIV is transmitted by Sexual contact with an infected person. Transfusion of contaminated blood. Sharing infected needles. Infected mother to unborn child through placenta. n Å n n n n n n n Cancer Å HIV/AIDS spreads only through body fluids. There is always a time-lag between the infection and appearance of AIDS symptoms, i.e. it varies from a few months to many years (usually 5-10 years). It is the major cause of death all over the globe. It is caused by the breakdown of normal regulatory mechanisms of cell growth. Å Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Å Cancer cells, however lose this property and continue to divide giving rise to masses of cells called tumours. Tumours are of two types–benign and malignant. n n n Mode of HIV Infection Å Virus enters the macrophage after entering the body of a person. Å RNA gets replicated to form viral DNA by enzyme reverse transcriptase. Å Viral DNA gets incorporated into the host cell DNA and directs the infected cells to produce viruses. Å Discouraging unsafe sex and encouraging regular checkups. Individuals who are susceptible to infection are Drug addicts due to intravenous drug injections. Involved with multiple sexual partners. Require repeated blood transfusion. Children born to HIV positive mother. n Å Role of WHO to prevent HIV infection. Making blood (from blood banks) safe from HIV. Ensure use of disposable syringes and needles. Ensure keeping blood banks safe from HIV. Free distribution of condoms. Prevention of drug abuse. n n Å National AIDS Control Organisation (NACO) (1991) and other NGOs educate peoples about AIDS. Macrophages continue to produce virus particles and act like HIV factory. Å n n Benign tumours normally remain confined to their original location and do not spread to other parts of the body and cause little damage. Malignant tumours are a mass of proliferating cells called neoplastic or tumour cells. These cells grow very rapidly, invading and damaging the surrounding normal tissues. NEET KEY NOTES www.mediit.in Master The NCERT > Biology (Vol-II ) 194 n n As these cells actively divide and grow, these also starve the normal cells by competing for vital nutrients. Cells sloughed from malignant tumours reach distant sites through blood and wherever they get lodged in the body, they start a new tumour there. This property is called metastasis. Causes of Cancer Carcinogens are cancer-causing agents. These are n n n Å Drugs and Alcohol Abuse The use of drugs and alcohol has risen especially among the youth. This is a cause of concern as it results in many harmful effects. The drugs which are commonly abused are as follows Å Chemicals Cigarette smoke (cause lung cancer) benzopyrene, dyes, paints, etc. Biological Oncogenic viruses, some parasites, etc. Cancer causing viruses called oncogenic viruses have genes called viral oncogenes. Normal cells have genes called cellular oncogenes (C-one) or proto-oncogenes which are present in inactive state, but under certain conditions (like mutation) get transferred to cancer-causing oncogenes. n n n Å Cancer can be detected by the following methods Å Blood and bone marrow tests to know number of cell counts. Å Biopsy of a piece of suspected tissue done by cutting in thin sections, stained and examined under microscope. Å Radiography by X-rays to detect cancer of the internal organs. Å Computed tomography using X-rays to generate a 3D image of internal tissue. Å Resonance imaging involves use of non-ionizing radiation and strong magnetic field to detect pathological and physiological changes in living tissue. Å Monoclonal antibodies against cancer-specific antigens are also used for cancer detection. Å Treatment of cancer involves the following methods Å Surgery Tumours are removed by surgery to check further spread of cancer cells. Å Radiation therapy Tumour cells are irradiated by a lethal dose of radiation by protecting the surrounding normal cells. Å Chemotherapy Several chemotherapeutic drugs are used to kill cancer cells. But, their side effects like hair loss, anaemia is also reported. NEET Heroine is obtained from the acetylation of morphine, which is extracted from the latex of poppy plant, Papaver somniferum. It is taken either by snorting or through injection. Heroine is a depressant which slows down the body functions. Morphine is an effective sedative, pain killer and very useful in patients who have undergone surgery. Cannabinoids are a group of chemicals which interact with cannabinoid receptors present mainly in brain. Cannabinoids are obtained from the inflorescence of the plant Cannabis sativa. Leaves, flower tops, resins of C. sativa in various combinations produce hashish, charas, marijuana and ganja. These are inhaled or ingested orally. n n n These drugs affect cardiovascular system of the body. Coca alkaloids or Cocaine has a potent stimulating action on the central nervous system, producing a sense of euphoria and increased energy. n Å n n Molecular biology technique to detect genes in individual with inherited susceptibility to certain cancers. Treatment of Cancer Opioids are the drugs which binds to specific opioid receptors present in our central nervous system and gastrointestinal tract. Heroin is a common opioid and is also called as smack. It is chemically diacetylmorphine, white, odourless, bitter crystalline compound. n Physical Ionizing radiation like X-rays and γ-rays, non-ionizing radiations like UV-rays (cause DNA damage leading to neoplastic transformation). Cancer Detection and Diagnosis Immunotherapy biological modifiers like α-interferons are used to activate the immune system and help in destroying the tumour. n Å Cocaine is derived from the leaves and young branches of a South American plant called Erythroxylum coca. Its mode of intake is either sniffting or snorting. It is a strong stimulant and when taken in overdose causes headache, convulsions, hallucination and death due to cardiovascular or respiratory failure. Hallucinogens are psychedelic drugs because of their effect on the cerebrum and sense organs. n n n These are obtained from plants like Atropa belladonna and Datura species. Lysergic acid diethyl amide (LSD) is derived from the fungus Claviceps purpurea. Effect of these drugs occurs on thoughts, feelings and perceptions of an individual. Drugs like barbiturates, comphetamines, benzodiazepines, etc., normally used as medicines. KEY NOTES www.mediit.in 195 CHAPTER 08 > Human Health and Diseases Å Tobacco contains nicotine which stimulates the adrenal gland to release adrenaline and nor-adrenaline which in turn increases the blood pressure and heart rate. n n n n Addiction and Dependence Å Addiction is the psychological attachment to certain effects-such as euphoria and a temporary feeling of well-being associated with drugs and alcohol. Å Dependence on drug/alcohol is the tendency of the body to manifest a characteristic and unpleasant withdrawl syndrome, if regular dose of drugs/alcohol is discontinued abruptly. Withdrawl symptoms are characterised by anxiety, shakiness, nausea and sweating. It is obtained from tobacco plant. Its mode of intake is smoking, chewing or can be used as a snuff. Tobacco can induce lung cancer, bronchitis, emphysema, coronary heart disease, cancer of throat, oral cancer, urinary bladder cancer, etc. Smoking of tobacco leads to increase in carbon monoxide content of blood and reduces the concentration of haem-bound oxygen. This leads to oxygen deficiency in the body. Adolescence and Drug/Alcohol Abuse Adolescence is the period during which a child becomes mature in terms of his/her attitudes and beliefs for independent participation in the society. Å Age between 12-18 years is called adolescent period. Å Adolescence is accompanied by several biological and behavioural changes. It is a vulnerable phase of mental and psychological developemnt of an individual. Å In this age use of drugs or alcohol occurs out of curosity or experimentation which later turns to addiction. Effects of Drug/Alcohol Abuse The common warning signals of drug/alcohol addiction are Å Drop in academic performance. Å Isolation from family and friends. Å Lack of interest in personal hygiene. Å Aggressive and rebellious behaviour. Å Reckless behaviour, vandalism and violence. Prevention and Control The preventive measures are Å Avoid undue peer pressure. Å Accept failures and disappointments as part of life. Å Seek help from parents and peers. Å Seek professional and medical help for deaddiction. Å Look for danger signs. Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Human Health and Common Diseases in Humans 1 Which of the following adversely affects human health? (a) Change in lifestyle (c) Rest and exercise (b) Genetic disorders (d) Both (a) and (b) 2 Health is a combination of I. physical fitness II. presence of disease III. mental and social well-being Which of the options given above are correct? (a) I and II (c) II and III (b) I and III (d) I, II and III 3 Human health cannot be maintained by (a) (b) (c) (d) maintaining personal hygiene consuming a diet rich in carbohydrate only regular physical exercise None of the above 4 Necessary steps for achieving good health are I. awareness about diseases. II. vaccination. III. proper disposal of wastes. The correct combination having necessary steps are (a) I, II and III (c) I, III and IV (b) II, III and IV (d) II and IV 5 Measures for personal hygiene include. (a) (b) (c) (d) Intake of clean drinking water Keeping the body clean Disinfection of water resources Both (a) and (b) 6 A disease which can easily transmit from one person to another is called (a) non-infectious disease (b) infectious disease (d) bacterial disease (c) viral disease www.mediit.in Master The NCERT > Biology (Vol-II ) 196 7 Which one of the following disease is non-infectious 15 Which of the following sets of diseases are caused by as well as the major cause of death in humans? bacteria? (a) Cancer (c) Asthma (a) Cholera and tetanus (c) Tetanus and mumps (b) AIDS (d) Typhoid 8 Identify the correct pair representing the causative agent of typhoid fever and the confirmatory test for typhoid. NEET 2019 (a) Streptococcus pneumoniae/Widal test (b) Salmonella typhi/Anthrone test (c) Salmonella typhi/Widal test (d) Plasmodium vivax/UTI test 9 Salmonella typhi generally enters the small intestine through .......A......... and migrates to other body parts through ........B........ . The most appropriate combination to fill the blanks is (a) (b) (c) (d) A–contaminated food and water; B–blood A–contaminated food; B–blood A–skin; B–blood A–air; B–blood 10 Common symptoms of typhoid are (a) (b) (c) (d) high fever 39°C to 40°C and weakness stomach pain and constipation headache and loss of appetite All of the above 11 The name of Mary Mallon is related with the disease (a) typhoid (c) dengue (b) pneumonia (d) AIDS 12 Pneumonia is an infection of the ......A...... . The most common cause of pneumonia is a type of bacteria known as .....B.... and .....C....... . Most suitable combination to fill the blanks is (a) A–liver, B– Salmonella typhi, C–Streptococcus pneumoniae (b) A–lungs, B–Streptococcus pneumoniae, C–Haemophilus influenzae (c) A–blood, B–Streptococcus pneumoniae, C–Haemophilus influenzae (d) A–heart, B–Salmonella typhi, C–Haemophilus influenzae 13 Which of the following health disorder includes symptoms of fever, chills, cough, headache, grey to bluish lips and fingers nails? (a) Filariasis (c) Pneumonia (b) Typhoid (d) Malaria 14 Infection of pneumonia occurs due to (a) droplets released from an infected person (b) released droplets/aerosols inhaled by healthy person (c) sharing contaminated objects such as glasses and utensils with an infected person (d) All of the above NEET 2016 (b) Typhoid and smallpox (d) Herpes and influenza 16 Rhinovirus causes (a) common cold (c) AIDS (b) malaria (d) pneumonia 17 Common cold differs from pneumonia in, that CBSE-AIPMT 2012 (a) pneumonia is a communicable disease, whereas the common cold is a nutritional deficiency disease (b) pneumonia can be prevented by a live attenuated bacterial vaccine, whereas the common cold has no effective vaccine (c) pneumonia is caused by a virus, while the common cold is caused by the bacterium Haemophilus influenzae (d) pneumonia pathogen infects alveoli whereas the common cold affects nose and respiratory passage but not the lungs 18 Which of the following viruses is not transferred through semen of an infected male? CBSE-AIPMT 2015 (a) (b) (c) (d) Hepatitis-B virus Human immunodeficiency virus Chikungunya virus Ebola virus 19 Female Anopheles mosquito is a vector of (a) filariasis (c) typhoid (b) malaria (d) AIDS 20 Malaria is caused by (a) Plasmodium vivax (b) Plasmodium malariae (c) Plasmodium falciparum (d) All of the above 21 Malignant malaria is caused by (a) Plasmodium falciparum (b) Plasmodium ovale (c) Plasmodium vivax (d) Plasmodium malariae 22 Where will you look for the sporozoites of the malarial parasite? (a) RBCs of humans suffering from malaria (b) Spleen of infected person (c) Salivary glands of freshly moulted female Anopheles mosquito (d) Saliva of infected female Anopheles mosquito 23 Infective stage of Plasmodium for man is (a) merozoites (c) sporozoites (b) ookinetes (d) None of these 24 Which of the following toxic substances is responsible for the high malarial fever? (a) Haemoglobin (c) Haemozoin (b) Haemocyanin (d) Haemoriden www.mediit.in 197 CHAPTER 08 > Human Health and Diseases 25 Plasmodium completes its life cycle in two hosts. Asexual phase in …… host and sexual phase in …… host. The correct option with words to fill the blanks is (a) (b) (c) (d) human; Culex mosquito human; female Anopheles mosquito human; Aedes mosquito human; male Anopheles mosquito (a) Plasmodium (c) houseflies (a) large intestine (c) lungs (b) Entamoeba histolytica (d) contaminated food and water (b) liver (d) kidney 31 Which one is not a symptom of disease caused by E. histolytica ? (b) male Culex (d) female Anopheles 27 Study the given diagram and name the labelled A, B, C and D. (a) (b) (c) (d) Stools with excess mucus and blood clots Constipation smacked Abdominal pain and cramps Nasal discharge 32 Which of the following is a protozoan disease? When the mosquito bites another human, sporozoites are injected with bite. Mature infective stages (sporozoites) escape from gut and migrate to the mosquito salivary glands. organism 30 Entamoeba histolytica is a parasite of 26 The primary host of Plasmodium is (a) man (c) sheep 29 Amoebiasis (amoebic dysentery) is caused by (a) Malaria (c) Sleeping sickness (b) Amoebiasis (d) All of these 33 Which of the following disease is caused by a protozoan? (a) Syphilis (c) Babesiosis Sporozoites Salivary glands (A) CBSE-AIPMT 2015 (b) Influenza (d) Blastomycosis 34 Which of the following endoparasites of humans does show viviparity? (D) Female mosquito takes up gametocytes with blood meal. Mosquito Host es cyt Human Host The parasite reproduces asexually in liver cells, bursting the cell and releasing into the blood. to me Ga ascariasis and filariasis, respectively. Male (C) (a) A–Sporozoites in spleen, B–Sexual reproduction of Plasmodium in RBC, C–Gametocytes in RBC, D–Fertilisation of gametocytes in mosquito’s intestine (b) A–Sporozoites in liver, B–Asexual reproduction of Plasmodium in RBC, C–Gametocytes in RBC, D–Fertilisation of gametocytes in mosquito’s intestine (gut) (c) A–Sporozoites in liver, B–Asexual reproduction of Plasmodium in RBC, C–Gametocytes in RBC, D–Fertilisation of gametocytes in mosquito’s salivary glands (d) A–Sporozoites in kidney, B–Sexual reproduction of Plasmodium in RBC, C–Gametocytes in RBC, D–Fertilisation of gametocytes in mosquito’s intestine 28 Which one of the following diseases is spread by (a) (b) (c) (d) Dengue fever Encephalitis Filariasis Amoebiasis CBSE-AIPMT 2015 Ancylostoma duodenale Enterobius vermicularis Trichinella spiralis Ascaris lumbricoides 35 Give the name of two helminths, which cause Female (B) housefly? (a) (b) (c) (d) (a) (b) (c) (d) Ascaris and Wuchereria Wuchereria and Ascaris Roundworm and flatworm Plasmodium and Wuchereria 36 Which of the following diseases causes internal bleeding, muscular pain, fever, anaemia and blockage of the intestinal passage? (a) Ascariasis (c) Amoebiasis (b) Filariasis (d) Trypanosomiasis 37 Infection of Ascaris usually occurs by (a) (b) (c) (d) NEET 2013 drinking water containing egg of Ascaris eating imperfectly cooked pork tse-tse fly mosquito bite 38 Elephantiasis, a chronic inflammation that results in gross deformities is caused by (a) Trichophyton (c) E. coli (b) Wuchereria (d) Ascaris 39 Elephantiasis causing organism belongs to (a) Aschelminthes (c) Cnidaria (b) Platyhelminthes (d) Porifera www.mediit.in Master The NCERT > Biology (Vol-II ) 198 40 The filariasis pathogen is transmitted to a healthy person through the bite of (a) (b) (c) (d) female Anopheles mosquito female Aedes mosquito female Culex mosquito None of the above 41 Adults of Wuchereria bancrofti attack (a) excretory system (c) lymphatic system AIIMS 2018 (b) digestive system (d) nervous system 42 In which disease does mosquito transmitted pathogen cause chronic inflammation of lymphatic vessels? NEET 2018 (a) Ringworm disease (c) Elephantiasis (b) Ascariasis (d) Amoebiasis 43 Which one of the following pairs is not correctly (a) Filariasis — Wuchereria (b) Syphilis — Trichuris trichiura (c) Plague — Yersinia pestis (d) Dengue fever — Flavi-ribo virus 44 The group of diseases carried (transmitted) by insects are typhoid, jaundice, tuberculosis mumps, measles, smallpox scabies, ringworm, swine flu malaria, filaria, yellow fever 45 The following table shows certain diseases, their causative organisms and symptoms. Diseases Causative organisms Symptoms I. Filariasis A Inflammation of lymphatic vessels II. Typhoid B High fever, stomach pain III. C IV. Ascariasis Rhinoviruses Nasal congestion and discharge Ascaris 46 Fungi belonging to genera–Microsporum, Trichophyton and Epidermophyton are responsible for (a) (b) (c) (d) ringworm infection skin allergy amoebiasis measles 47 Ringworm is a/an (a) air borne disease (b) infectious disease (c) non-infectious disease (d) None of these matched? (a) (b) (c) (d) The correct option regarding A, B , C and D is (a) A–Wuchereria, B–Salmonella typhi, C–Common cold, D–Internal bleeding, fever, anaemia (b) A–Salmonella typhi, B–Ascaris, C–Typhoid, D–Stomach pain, headache (c) A–Ascaris, B–Entamoeba histolytica, C–Pneumonia, D–Constipation, fever (d) A–Entamoeba histolytica, B–Salmonella typhi, C–Common cold, D–Nasal discharge, high fever D 48 Fill up the blanks. I. Heat and moisture help ............ fungi to grow, which makes them thrive in skin folds. II. Maintenance of ............ and ............ hygiene is important for the prevention of many infectious diseases. III. ............ gives the diseases its name, elephantiasis. (a) I. Microsporum, II. public; personal, III. Swelling of hand (b) I. Trichophyton, II. personal; public, III. Enlargement of eye (c) I. Epidermophyton, II. personal; public, III. Swelling of legs (d) I. Wuchereria, II. personal; public; III. Enlargement of tongue 49 Gambusia is a fish which can control the mosquito borne disease like (a) dengue (c) chikungunya (b) malaria (d) All of these TOPIC 2 ~ Immunity 50 Ability of the body to fight against the disease causing organisms is called (a) vulnerability (c) irritability (b) susceptibility (d) immunity 51 Innate immunity is also called (a) familiar immunity (c) genetic immunity (b) inborn immunity (d) All of these 52 Non-specific host defence that exists prior to the exposure to an antigen is called (a) acquired immunity (c) innate immunity (b) passive immunity (d) active immunity 53 Except skin, other physical barriers which also help to prevent the entry of the microorganisms are mucus coating of the epithelium lining of I. the respiratory tract. II. the gastrointestinal tract. III. the urogenital tract. Choose the correct option. (a) (b) (c) (d) I and II I and III II and III I, II and III www.mediit.in 199 CHAPTER 08 > Human Health and Diseases 54 Which type of barriers do saliva in the mouth, tears form eyes and acid in the stomach belong? (a) Cytokinin barriers (b) Cellular barriers (c) Physiological barriers (d) Physical barriers 55 Full form of PMNL is (a) (b) (c) (d) Poly Morpho-Nuclear Leucocytes Para Morpho-Nuclear Lymphocytes Penta Morpho-Nuclear Leucocytes Poly Morpho-Nuclear Lymphocytes (b) antigen (d) macrophages 57 Which of the following are considered as cellular barrier of the body? (a) Lymphocytes (c) Macrophages (a) proteins produced in response to pathogens in our body (b) secreted by the action of both T-lymphocytes and B-lymphocytes (c) molecules that specifically interacts with an antigen (d) Both (a) and (b) 65 Each antibody has ...A... polypeptide chains, ..B.. 56 The major phagocytic cells are (a) antibody (c) lymphocytes 64 Antibodies are (b) Neutrophils (d) All of these 58 Humans have acquired immune system that produces antibodies to neutralise pathogens. Still innate immune system is present at the time of birth because NEET (Odisha) 2019 it (a) is very specific and uses different macrophages (b) produces memory cells for mounting fast secondary response (c) has natural killer cells which can phagocytose and destroy microbes (d) provides passive immunity small chains called ...C... chains and ....D... longer chains called ...E... chains. The antibody, therefore, is represented as ... F.. Here A to F refers to (a) (b) (c) (d) A–four, B–two, C–light, D–two, E–heavy, F–H 2 L 2 A–six, B–three, C–light, D–three, E–heavy, F–H 3 L 2 A–two, B–one, C–light, D–one, E–heavy, F–H 1 L1 A–five, B–two, C–light, D–three, E–heavy, F–H 2 L 2 66 Antigen binding site of immunoglobulin (antibody) is (a) (b) (c) (d) variable region of heavy chain variable region of light chain constant region of light chain variable region of both heavy and light chain 67 The figure given below shows an antibody molecule. Name the parts A, B and C. A s 59 Which of the following is a suitable example of cytokine barrier? (a) Interferons (c) B-lymphocytes (b) T-lymphocytes (d) T H cells s s C 60 The interferons can be used as (a) antibacterial drugs (c) antibiotic drugs s s s s s s B homeostatic disorder hepatitis caused by virus common cold caused by virus Both (b) and (c) (a) typhoid (b) filariasis (c) malaria 63 Note the following words. I. Skin II. III. B-cells IV. V. Antibodies VI. VII. Macrophages VIII. (d) measles Phagocytes Neutrophils T-cells NK-cells Identify the factors involved in second line of defence. (a) II, IV, VII and VIII (c) IV, VI, VIII and VIII (b) II, III, V and VI (d) III, V, VII and VIII s s s ss ss counter seems to carry an infection of s ss ss (b) antiviral drugs (d) immunosuppressive 62 A person has developed interferons in his body. He s s 61 Interferon is a type of protein, which can be used to (a) (b) (c) (d) s s s s s D ss ss ss (a) A–Antigen binding site, B–Heavy chain, C–Light chain, D–Disulphide bond (b) A–Antibody binding site, B–Light chain, C–Heavy chain, D–Phosphoester bond (c) A–Antigen binding site, B–Short chain, C–Long chain, D–Sulphur bond (d) A–Antibody binding site, B–Long chain, C–Short chain, D–Disulphide bond 68 The most abundant class of Immunoglobulins (Igs) in the human body is (a) IgA (c) IgG (b) IgM (d) IgE www.mediit.in Master The NCERT > Biology (Vol-II ) 200 80 Choose the correct option regarding antibodies. 69 Humoral immunity is also called as (a) (b) (c) (d) (a) (b) (c) (d) antibody mediated immunity non-specific immune response antigen mediated immunity None of the above 70 Humoral immunity is mediated by (a) B-cells (c) macrophages 81 The principle of vaccination or immunisation depends (b) T-cells (d) monocytes on the property of ..... of the immune system. The most appropriate word to fill the blank is 71 Humoral immune system defends against viruses and bacteria is present in (a) blood (c) Both (a) and (b) (b) lymph (d) None of these carried out by (a) memory (c) pathogen (b) antigen (d) plasma cells 82 Which form of pathogen is used in vaccination? 72 The cell-mediated immunity inside the human body is (a) T-lymphocytes (c) thrombocytes JIPMER 2019 IgA - Helps in allergic reaction IgG - Cross placenta IgE - Found in secretions IgM - Exist as dimer NEET 2013 (b) B-lymphocytes (d) erythrocytes (a) Activated and strong pathogens (b) Preformed antigens and antibody (c) Inactivated and weakened pathogenic agents (d) None of the above 83 If a quick immune response is needed as in tetanus damaged tissues or organs like heart, eye, liver, kidney with healthy ones from a donor is called as infection, preformed antibodies or antitoxin is injected into the patient body. This type of immunisation is called ……… . (a) transplantation (b) repair and replacement (c) replacement theraphy (d) transformation (a) active immunisation (c) innate immunity 73 The process of removal and replacement of the 74 Which of the following immune responses is responsible for rejection of kidney graft? NEET 2019, CBSE-AIPMT 2015 (a) (b) (c) (d) Humoral immune response Inflammatory immune response Cell-mediated immune response Auto-immune response (b) exposure to live pathogen (d) Both (a) and (b) (b) memory cells (d) suppressor T-cells (a) transfer of lymphocyte directly (b) transfer of maternal antibodies across placenta to the foetus (c) introduction of antibodies directly in the body (d) Both (b) and (c) 78 Colostrum, the yellowish fluid, secreted by mother during the initial days of lactation is very essential to impart immunity to the new born infants because it contains NEET 2019 (b) macrophages (d) natural killer cells 79 Which of the following is involved in passive immunity? (a) IgA (c) IgM JIPMER 2018 (b) IgE (d) IgD (b) gamma globulin (d) activated pathogens (a) yeast (c) bacteria (b) bacteriophage (d) All of these 86 A substance that causes an allergic reaction is called (a) allergen (c) foreign substance (b) pollen (d) dander 87 Which of the following mediates allergic reaction? JIPMER 2018 77 Passive immunisation includes (a) monocytes (c) immunoglobulin-A while polio drops that are administered into the body NEET 2016 contain 85 Hepatitis-B vaccine is produced from 76 Active immunity development is related to (a) natural killer cells (c) helper T-cells 84 Antivenom injection contains preformed antibodies (a) harvested antibodies (c) attenuated pathogens 75 Active immunity is an immunity gained after (a) natural infection (c) immunisation (b) passive immunisation (d) humoral immunity (a) IgA (b) IgG (c) IgE (d) IgD 88 Common examples of allergens are (a) dust (c) animal dander (b) pollen grains (d) All of these 89 An allergic response appears at the site of infection causes sneezing, watery eyes, running nose, pain and heat due to the certain chemicals (allergens), they are (a) histamine and serotonin (b) histamine and cerumen (c) cerumen and serotonin (d) mucus and cerumen 90 What is injected into the patient’s body for determining the cause of allergy? (a) (b) (c) (d) Allergen to which the patient is allergic IgG IgE Steroids www.mediit.in 201 CHAPTER 08 > Human Health and Diseases 91 Which of the following drugs can be used to quickly reduce the symptoms of allergic reaction? I. Anti-histamine II. Adrenaline III. Steroids (a) I and II (c) II and III and beneath the ....B.... . The most appropriate combination for A and B is (a) (b) (c) (d) (b) I and III (d) I, II and III 92 Asthma may be attributed to NEET 2016 (a) allergic reaction of the mast cells in the lungs (b) inflammation of the trachea (c) accumulation of fluid in the lungs (d) bacterial infection of the lungs 93 In higher vertebrates, the immune system can distinguish self and non-self cells. If this property is lost due to the genetic abnormality and it attacks self-cells, then it leads to NEET 2016 (a) graft rejection (b) autoimmune disease (c) active immunity (d) allergic response disorder? NEET (Odisha) 2019 (b) Arthritis (d) Gout 95 Which of the following is not an autoimmune disease? (a) (b) (c) (d) A–heart; B–breast bone A–liver; B–ribs A–heart; B–ribs A–intestine; B–ribs 100 What is the main lymphoid organ where all blood cells including lymphocytes are produced? (a) Bone marrow (c) Liver (b) Tonsils (d) Spleen 101 T-lymphocytes mature in the ........... while B-lymphocyte mature in the ........ . Most appropriate combination of words to fill the blanks is (a) (b) (c) (d) thymus; bone marrow bone marrow; thymus thyroid; bone marrow yellow bone marrow; red bone marrow 102 Full form of MALT is 94 Which of the following diseases is an autoimmune (a) Myasthenia gravis (c) Osteoporosis 99 Thymus is a lobed organ located near the...... A ..... NEET 2018 (a) (b) (c) (d) Mucosal Associated Lymphoid Tissue Memory Associated Lymphoid Tissue Memory Associated Lymphocyte Tissue Mucosa Associated Lymphocyte Tissue 103 MALT constitutes about ...…… per cent of the lymphoid tissue in human body. (a) 50% (c) 70% Alzheimer’s disease Rheumatoid arthritis Psoriasis Vitiligo NEET 2017 (b) 20% (d) 10% 104 Given below the diagrammatic representation of lymph nodes. 96 The site where immature lymphocytes differentiate into antigen sensitive lymphocytes are (a) (b) (c) (d) primary lymphoid organs secondary lymphoid organs lymph nodes tonsils A B 97 Which of the given sets include the primary lymphoid organs? (a) (b) (c) (d) Thymus, lymph nodes and spleen Bone marrow and thymus Bone marrow, Peyer’s patches and thymus Thymus, liver and tonsils 98 Surgical removal of thymus of a newborn shall result in the failure to produce (a) Allergens (c) B-lymphocyte (b) Interferons (d) T-lymphocytes C Label A, B and C. (a) (b) (c) (d) A–Lymph nodes, B–Thymus, C–Lymphatic vessels A–Lymphatic vessels, B–Thyroid, C–Lymph nodes A–Tonsils, B–Peyer’s patchs, C–Lymphatic vessels A–Tonsils, B–Thymus, C–Peyer’s patches www.mediit.in Master The NCERT > Biology (Vol-II ) 202 TOPIC 3 ~ AIDS (Acquired Immuno Deficiency Syndrome) (a) A–Bacteriophage, B–Viral DNA is produced, C–New viral RNA is produced 105 Human immunodeficiency virus causes (a) (b) (c) (d) Acquired Immuno Deficiency Syndrome Anthrax tuberculosis polio 106 Genetic material found in Human Immunodeficiency Virus (HIV) is (a) (b) (c) (d) double-stranded RNA single-stranded RNA double-stranded DNA single-stranded DNA 110 HIV is a ....A...... and has genetic material composed of 107 AIDS virus contains (a) (b) (c) (d) (b) A–Transcriptase, B–Bacterial RNA is produced, C–New viral DNA is produced by the infected cell (c) A–Bacteriophage, B–Viral DNA is produced, C–New viral RNA is produced by the infected cell (d) A–Retrovirus, B–Viral DNA is produced by reverse transcriptase, C–New viral RNA is produced by the infected cell ...B...., HIV replicates inside the host cells. It is considered a retrovirus because it uses an enzyme, ....C.... , to convert ...... D...... into .......E...... . Here A to E refers to RNA with protein DNA with protein RNA without protein Only DNA 108 Transmission of HIV infection from infected mother to her child occurs through (a) liver (b) placenta (c) skin (d) None of these 109 In the given flow chart, the replication of retrovirus in a host cell is shown. Observe it carefully and fill up the blank A, B and C. (A) (a) A–retrovirus, B–RNA, C–reverse transcriptase, D–RNA, E–DNA (b) A–retroviral, B–DNA, C–reverse transcriptase, D–DNA, E–RNA (c) A–rhinovirus, B–DNA, C–reverse transcriptase, D–DNA, E–RNA (d) A–adenovirus, B–RNA, C–reverse transcriptase, D–RNA, E–DNA 111 In an infected human body the ‘HIV factory’ is (a) sperm (c) macrophages (b) ova (d) spleen cells 112 At which stage of HIV infection does one usually Virus infects normal cell Plasma membrane Animal cell (B) Cytoplasm Viral DNA incorporates into host genome show symptoms of AIDS? CBSE-AIPMT 2014 (a) Within 15 days of sexual contact with an infected person (b) When the infected retrovirus enters host cells (c) When HIV damages large number of helper T-lymphocytes (d) When the viral DNA is produced by reverse transcriptase 113 A patient is suspected to be suffering from Acquired Immuno Deficiency Syndrome (AIDS). Which diagnostic technique will you recommend for its detection? (C) (a) ELISA Nucleus DNA (b) MRT (c) Ultrasound (d) WIDAL 114 The word NACO stands for (a) (b) (c) (d) National AIDS Control Organisation Non-governmental AIDS Control Organisation National Agrochemical Organistation Both (b) and (c) www.mediit.in 203 CHAPTER 08 > Human Health and Diseases TOPIC 4 ~ Cancer 115 The property of normal cells by virtue of which contact with other cells inhibits their uncontrolled growth is called (a) contact inhibition (c) benign tumour (b) metastasis (d) metagenesis 116 Cell division or mitosis is a normal process in living cells but sudden and abnormal mitosis in an organ will frequently result in (a) zygote (c) new organ (b) cancer (d) gastrula 117 The uncontrolled proliferation of cancerous cells produces masses of cells, called (a) tumours (c) protooncomass (b) neoplastic cells (d) Both (a) and (b) 118 Which form of tumour remains confined to their original location and do not spread to other parts of the body? (a) Malignant tumour (c) Both (a) and (b) (b) Benign tumour (d) Leukaemia 119 Which of the following properties is possessed by malignant tumours? (a) (b) (c) (d) Metastasis Uncontrolled cell division Both (a) and (b) Controlled cell division cancerous cells, whereas the remaining three are? CBSE-AIPMT 2012 (a) They compete with normal cells for vital nutrients (b) They do not remain confined in the area of formation (c) They divide in an uncontrolled manner (d) They show contact inhibition 121 Transformation of normal cell into cancerous cell is induced by (b) lipids (d) All of these 122 Physical carcinogens, e.g. UV-ray, X-ray and γ-rays cause (a) DNA damage (c) Both (a) and (b) (b) RNA damage (d) Protein damage 123 Chemical carcinogens present in tobacco smoke have been identified as a major cause of (a) lung cancer (c) oral cancer (a) oncogenic viruses (c) adenoviruses (b) retroviruses (d) poxviruses 125 The genes which can lead to the oncogenic transformation of the cells in which these are present, are called (a) oncogenes (c) cellular oncogenes (b) proto-oncogenes (d) Both (b) and (c) 126 Normal cell have genes called ........A..... which are present in inactivated state but under certain conditions like .....B... they get transformed to ...C.... Here A, B and C refers to (a) A–cellular oncogenes, B–mutation, C–cancer causing oncogenes (b) A–viral oncogenes, B–mutation, C–disease causing genes (c) A–viral oncogenes, B–mutation, C–tumour causing genes (d) None of the above 127 Characteristics of cancer are (a) (b) (c) (d) AIIMS 2018 All viruses are oncogenic All tumours are cancers Cancerous cells show property of contact inhibition Cancer cells show metastasis 128 Which of the following techniques is used to detect 120 Which one of the following is not a property of (a) carcinogens (c) proteins 124 Cancer causing viruses are called (b) liver cancer (d) None of these the of cancer of internal organs? (a) (b) (c) (d) Magnetic Resonance Imaging (MRI) Radiography (X-ray) Computed Tomography (CT) scan All of the above 129 Cancer cells are more easily damaged by radiation than normal cells because they are (a) (b) (c) (d) starved of mutation undergoing rapid division different in structure non-dividing 130 Treatment and detection of cancer can be done by (a) radiography (c) surgery (b) chemotherapy (d) All of these 131 Alpha-interferons (a) (b) (c) (d) activate the immune system help in destroying the tumour Both (a) and (b) None of the above www.mediit.in Master The NCERT > Biology (Vol-II ) 204 TOPIC 5 ~ Drug and Alcohol Abuse 132 Opioids are the drugs, which bind to specific opioid 141 Observe the molecules A and B given below and select the right option giving their use and source. receptors present in our HO (a) central nervous system (b) gastrointestinal tract (c) Both (a) and (b) (d) urinogenital system OH O 133 Smack is chemically .....A..... which is white and odourless and crystalline in nature. This is obtained by ....B.... . Here A and B refers to (a) (b) (c) (d) A–diacetylmorphine; B–acetylation of morphine A–morphine; B–acetylation of hashish A–stimulant; B–acetylation of morphine A–hallucinogen; B–acetylation of hashish 134 Durg called ‘heroin’ is synthesised by (a) (b) (c) (d) acetylation of morphine glycosylation of morphine nitration of morphine methylation of morphine NEET 2019 135 Which part of poppy plant is used to obtain the drug smack? (a) Roots (c) Flowers NEET 2018 (b) Latex (d) Leaves 136 A drug called heroin is obtained from (a) (b) (c) (d) Rauwolfia serpentina Cannabis sativa Cajanus cajan Papaver somniferum interact with cannabinoid receptors present principally in (a) brain (c) nephron (b) neuron (d) dendron 138 Cannabinoids are obtained from (a) (b) (c) (d) HO B Cannabinoid A Morphine Molecules inflorescence of the plant Cannabis sativa fruits of the plant Papaver somniferum latex of the plant Cannabis sativa plant Papaver somniferum inflorescence Taken by Uses (a) A–Morphine Sedative and pain killer (b) B–Morphine Product marijuana Oral ingestion (c) A–Cannabinoid Produces hallucinations inhalation (d) B–Cannabinoid Accelerates the transport of dopamine injection Snorting and injection 142 Coca alkaloid or cocaine is obtained from NEET (Odisha) 2019 (a) Papaver sonmiferum (c) Erythoxylum coca (b) Atropa belladonna (d) Datura 143 Cocaine is commonly called as (a) coke (c) Both (a) and (b) 137 Cannabinoid are the group of chemicals, which HO N—CH3 H (b) crack (d) smack 144 Traditional anesthesia is obtained from JIPMER 2019 (a) Datura (b) poppy (c) Cannabis (d) Erythoxylum 145 Which one of the following is a stimulant? (a) LSD (b) Cocaine (c) Opium (d) Heroin 146 Plants with hallucinogenic properties are (a) Atropa belladonna (c) Both (a) and (b) (b) Datura (d) Papaver 147 Identify the pictures A, B and C. 139 The flower tops, leaves and the resin of Cannabis sativa are used to produce (a) marijuana (c) charas (b) hashish (d) All of these 140 The drug that produces profound cardiovascular effects in human beings is (a) cocaine (c) benzodiazepine (b) ganja (d) insulin A (a) (b) (c) (d) B C . A–Opium poppy, B–Cannabis sativa, C–Datura A–Cannabis sativa, B–Opium poppy, C–Datura A–Datura, B–Opium poppy, C–Cannabis sativa A–Opium poppy, B–Datura, C–Cannabis sativa www.mediit.in 205 CHAPTER 08 > Human Health and Diseases 148 Which is the particular type of drug that is obtained from the plant whose one flowering branch is shown below? CBSE-AIPMT 2014 156 In heavy smokers, the alveoli of the lungs are enlarged and damaged, which reduces the surface area for the exchange of respiratory gases. This condition is called (a) (b) (c) (d) asthma silicosis emphysema insomnia 157 Carcinogen present in cigarette smoke is (a) benzopyrene (c) carbon monoxide (b) nicotine JIPMER 2019 (d) All of these 158 Those who take drugs intravenously develop a risk of (a) Hallucinogen (c) Stimulant (b) Depressant (d) Pain killer 149 Drugs, that are normally used as medicines to help the (a) AIDS (c) Both (a) and (b) (b) hepatitis-B (d) malaria 159 Cirrhosis of liver is caused by the chronic intake of CBSE-AIPMT 2012 patients cope with mental illness are (a) barbiturates (c) benzodiazepines (b) amphetamines (d) All of these 150 LSD is derived from (a) Claviceps purpurea (c) Cannabis indica (b) Pseudomonas putida (d) Cannabis sativa 151 Which one of the following is a correct matching pair of a drug and its category? (a) (b) (c) (d) Amphetamines Lysergic acid diethylamide Heroin Benzodiazepies — Stimulant — Narcotic — Psychotropic drug — Pain killer 152 Which one of the following fungi contains hallucinogens? (a) Morchella esculenta (c) Neurospora sp. CBSE-AIPMT 2014 (b) Amanita muscaria (d) Ustilago sp. 153 Nicotine is (a) an alkaloid (c) a stimulant (b) a steroid (d) Both (a) and (c) 154 Nicotine intake stimulates the ....A... to release ...B.... and ....C.... into blood circulation. This lead to increase in ...D... and an increase.... E .... . Identify A to E. (a) A–adrenal gland, B–adrenaline, C–nor-adrenaline, D–blood pressure, E–heart rate (b) A–thyroid gland, B–thyroxine, C–parathyroxine, D–blood pressure, E–heart rate (c) A–adrenal gland, B–thyroxine, C–nor-adrenaline, D–blood pressure, E–heart rate (d) A–gonads B–adrenaline, C–nor-adrenaline, D–blood pressure, E–heart rate 155 Smoking addiction is harmful because smoke produces polycyclic aromatic hydrocarbons, which cause (a) (b) (c) (d) reduction in oxygen transport increase in blood pressure cancer retardation of growth of foetus (a) opium (c) tobacco (chewing) (b) alcohol (d) cocaine 160 Fill up the blanks. I. The period between ....A....years of age may be thought of as adolescence period. II. Adolescence is a bridge linking ....B .... and ....C.... III. The chronic use of drug and alcohol damages ...D.... and ...E... IV. Alcoholism during ....F.... adversely affects the foetus. (a) A–12-18, B–childhood, C–adulthood, D–nervous system, E–liver, F–pregnancy (b) A–10-15, B–adulthood, C–childhood, D–heart, E–stomach, F–adulthood (c) A–15-20, B–adulthood, C–childhood, D–liver, E–kidney, F–pregnancy (d) A–20-28, B–adulthood, C– childhood, D–liver, E–nervous system, F–pregnancy 161 Which part of the brain is involved in the loss of control over speech when a person consumes excessive alcohol? (a) (b) (c) (d) Cerebellum Medulla oblongata Cerebrum Pons varoli 162 Side effects of anabolic steroids in females include I. masculinisation. II. aggressiveness. III. mood swings, depression. IV. abnormal menstrual cycle. V. excessive facial and body hair. Choose the correct option. (a) (b) (c) (d) I, II and III I, II, III and IV II, III, IV and V I, II, III, IV and V www.mediit.in Master The NCERT > Biology (Vol-II ) 206 NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason 171 Assertion (A) Cancer cells are virtually immortal ■ Direction (Q. No. 163-177) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 163 Assertion (A) Escherichia coli, Shigella sp. and 164 165 166 167 168 169 170 Salmonella sp. are all responsible for diarrhoeal diseases. Reason (R) Dehydration is common to all types of diarrhoeal diseases and adequate supply of fluids and electrolytes should be ensured. Assertion (A) Interferons help to eliminate the viral infections. Reason (R) Interferons released by infected cells, reach the nearby uninfected cells and make them resistant to viral infection. Assertion (A) Interferons are a type of antibodies produced by body cells infected by bacteria. Reason (R) Interferons interferes with viral replication at the site of injury. Assertion (A) Antibody mediated immune response is provided by B-cells. Reason (R) B-cells work chiefly by secreting substances called antibodies into the body fluids. Assertion (A) A person who has received a cut and is bleeding needs to be given anti-tetanus treatment. Reason (R) Anti-tetanus injection stimulates the production of antibodies for tetanus. Assertion (A) Mast cells in the humans release excessive amount of chemicals like histamine, which cause allergy. Reason (R) Allergens in the environment on reaching human body stimulate mast cells. Assertion (A) Many visitors of hills suffer from skin and respiratory allergy problems. Reason (R) Pinus trees produce a large quantity of wind-borne pollen grains. Assertion (A) AIDS is a disorder caused by HIV. Reason (R) HIV is a virus that damages immune system of its host. 172 173 174 175 176 177 until the body in which they reside dies. Reason (R) Cancer is caused by damage to genes regulation of the cell division cycle. Assertion (A) Metastasis is the phenomenon in which tumour cells detach and migrate to other parts of the body where they give rise to secondary tumours. Reason (R) Abnormal antigens on the surface of cell and unusual number of chromosomes cause metastasis. Assertion (A) Cannabinoids are known for their effects on cardiovascular system of the body. Reason (R) Cannabinoids is a class of diverse chemical compounds that activates cannabinoid receptors present principally in brain. Assertion (A) Alcohol consumption during pregnancy is harmful. Reason (R) Alcohol causes physical and mental defects in the offspring called Foetal Alcohol Syndrome (FAS). Assertion (A) Dope test is used to estimate the level of alcohol by analysing the breathe of alcohol drinking person. Reason (R) Athletes undergo dope test before major tournaments or a match. Assertion (A) Repeated use of drugs, increases the tolerance level of receptors in our body. Reason (R) Addiction occurs as receptors respond only to higher doses of drugs. Assertion (A) Pork should be properly cooked to avoid Taenia infection. Reason (R) Pork of pig contains hexacanth and cysticercus larvae. II. Statement Based Questions 178 Which of the following statement(s) is/are correct regarding pathogens? I. A pathogen or an infectious agent is a microorganism, such as a virus, bacterium, fungus that causes disease in its host. II. Pathogens multiply in our body and interfere with the normal vital activities, resulting in morphological and functional damage. (a) Only I (c) I and II (b) Only II (d) None of these www.mediit.in 207 CHAPTER 08 > Human Health and Diseases 179 Which one of the following statements is correct with respect to immunity? CBSE-AIPMT 2012 (a) Preformed antibodies need to be injected to treat the bite by a viper snake (b) The antibodies against smallpox pathogen are produced by T-lymphocytes (c) Antibodies are protein molecules, each of which has four light chains (d) Rejection of a kidney graft is the function of B-lymphocytes 180 Which of the following is correct regarding AIDS causative agent HIV? NEET 2016 (a) HIV is enveloped virus containing one molecule of single-stranded RNA and one molecule of reverse transcriptase (b) HIV is enveloped virus that contains two identical molecules of single-stranded RNA and two molecules of reverse transcriptase (c) HIV is unenveloped retrovirus (d) HIV does not escape but attacks the acquired immune response 181 Consider the following statements. I. Adolescence is a very vulnerable phase of mental and psychological developments of individual. II. Adolescence is marked by accelerated physical growth, development of reproductive organs and changes in functioning of the neuroendocrine system. (a) (b) (c) (d) Both statements I and II are correct Both statements I and II are incorrect Statement I is correct, but II is incorrect Statement I is incorect, but II is correct 182 Choose the correct statements. I. Innate immunity is accomplished by providing different types of barriers. II. Acquired immunity is present from the birth and is inherited from parents. III. Acquired immunity can be divided into antibody mediated and cell-mediated immunity. IV. Innate immunity is also called specific immunity. V. Acquired immunity consists of specialised cells (T-cell and B-cell) and antibodies that circulate in the blood. Codes (a) I, II and V (c) I, III and V (b) II, III, IV and V (d) I, II, III, IV and V 183 Consider the following statements. I. People should get vaccination to avoid infection. II. Vaccination is available against polio, cholera, typhoid, tuberculosis and many other diseases. III. Eradication of vectors are necessary in diseases like malaria and filariasis. IV. Dengue and chikungunya, both are spread by Culex mosquitoes. Which of the statements given above are correct? (a) I, II and III (c) I, III and IV (b) I, II and IV (d) III and IV 184 Which of the following statements given below is/are correct? I. Secondary lymphoid organs includes lymph nodes, spleen and small masses of lymph tissue such as Peyer’s patches, appendix and tonsils. II. The secondary lymphoid organs provide the site for interaction of lymphocyte with the antigens. (a) Only I (c) I and II (b) Only II (d) None of these 185 The lymph nodes I. are small solid structures along the lymphatic system. II. filter lymph fluid as it flows through them, trapping bacteria, viruses and other antigens, which are then destroyed by lymphocytes. Which of the statements given above is/are corrcet? (a) Only I (c) I and II (b) Only II (d) None of these 186 Read the statements about a certain organ and choose the correct option. I. It is a large bean-shaped organ. II. It mainly contains lymphocytes and phagocytes. III. It acts as a filter of the blood by trapping blood-borne microorganisms. IV. It is a large reservoir of erythrocyte. V. It is a secondary lymphoid organ. (a) Thymus (b) Tonsils (c) Appendix (d) Spleen 187 Select the true statements. I. Cancer detection is based on biopsy and histopathological study of the suspected tissue. II. In biopsy, the suspected tissue is cut into thin sections, stained and examined under microscope. III. Certain chemotherapeutic drugs are used to kill the cancerous cells, but majority of the drugs have side effects like hair loss, anaemia, etc. IV. MRI uses strong magnetic fields and ionising radiations to accurately detect pathological and physiological changes in the living tissues. V. Techniques like radiography (use of X-rays), CT (Computed Tomography) scan and MRI are very useful to detect cancers of the internal organs. (a) I and II (c) II and III (b) I and III (d) All statements are true 188 Which of the following statements given below is/are correct? I. Growing number of people are taking LSD and other drugs like barbiturates and amphetamines to help themselves to cope with mental illness. www.mediit.in Master The NCERT > Biology (Vol-II ) 208 II. Several plants, fruits and seeds having hallucinogenic properties have been used in folk-medicine. (a) (b) (c) (d) Statement I is true, but II is false Stetement I is false, but II is true Both statements I and II are true Both statements I and II are false 189 Warning signs of drug and alcohol abuse include I. drop in academic performance. II. absence from school/college. III. lack of interest in personal hygiene. IV. isolation, depression, fatigue, aggresssive and rebellious behaviour. Which of the statements given above are correct? (a) I, II and III (c) II, III and IV (b) I, III and IV (d) All of these 190 Reasons for alcohol abuse in adolescents are I. social pressure. II. curiosity and need for adventure, excitement and experiment. III. to escape from stress, depression and frustration. IV. to overcome hardships of daily life. Which of the statements given above are correct? (a) I, II and III (c) II, III and IV (b) I, III and IV (d) All of these 191 Read the following statements and select the incorrect one. (a) When the functioning of one or more organs or systems of the body is adversely affected, characterised by appearance of various signs and symptoms, i.e. we have a disease (b) Some of the infectious diseases like AIDS are fatal (c) Pathogens cause harm to the host by living in (or on) them (d) None of the above 192 Read the following statements and select the correct statements. I. Subsequent encounter with the same pathogen for the second time elicits a highly intensified secondary immune response. II. The vaccines generate B and T-cells that recognise the pathogen quikly on subsequent exposure and overwhelm the invaders with massive production of antibodies. (a) (b) (c) (d) Both statements I and II are correct Statement I is correct, but II is incorrect Statement I is incorrect, but II is correct Both statements I and II are incorrect 193 Which of the following statements are correct? I. The exaggerated response of the immune system to certain antigens present in the environment is called allergy. II. The allergic tendency is genetically passed from the parents to the offspring and is characterised by the presence of large quantities of IgG antibodies in the blood. III. Bone marrow and thymus are the organs where origin and/or maturation and proliferation of lymphocytes occur. IV. Immunisation is the process by which the body produces antibodies against the vaccine preventable diseases through administration of specific vaccines. (a) I and II (c) I, III and IV (b) II and IV (d) All of these 194 Select the correct statements. I. The word AIDS stands for Acquired Immuno Deficiency Syndrome. This means deficiency of immune system, acquired during the lifetime of an individual. II. AIDS was first reported in 1981 and the word ‘syndrome’ in this, means a group of symptoms. III. There is always a time-lag between the infection and appearance of AIDS symptoms, i.e. vary from a few months to many years (usually 5-10 years). IV. During HIV infection, the macrophages cells of body continues produce virus and in this way acts like a HIV factory. (a) I, II and III (c) I, and IV (b) I, III and IV (d) All of these 195 Read the given statements carefully. I. In India, NACO and other NGOs are doing a lot to educate people about AIDS. II. To prevent HIV infections, use of disposable needles and syringes in hospitals, use of condoms during sex, control of drug abuse is necessary. III. Ist December is celebrated as World AIDS Day. IV. AIDS is characterised by decrease in the number of killer T-cells. Which of the above statements are correct? (a) I, II and IV (c) I and III (b) I, II, III and IV (d) I and IV 196 Read the following statements and select the correct answer. I. Psychoactive drugs have the ability to alter the activity of the nervous system. II. Addiction is a psychological attachment to certain effects such as euphoria and temporary feeling of well-being associated with drugs and alcohol. III. When the drugs are taken for a purpose other than medicinal use or in amounts/frequency that impairs one’s physical, physiological or psychological functions, it constitutes drug abuse. IV. Smoking increases carbon monoxide content in blood and reduces the concentration of oxygen. This causes oxygen deficiency in the body. (a) I and II (c) I, II and IV (b) III and IV (d) I, II, III and IV www.mediit.in 209 CHAPTER 08 > Human Health and Diseases 197 Read the following statements and select the correct option. I. Dependence is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome if regular dose of drugs/alcohol is abruptly discontinued. II. Excessive doses of drugs may lead to coma and death due to respiratory failure, heart failure or cerbral hemorrhage. III. Education about harmful effects of drugs and alcohol, counselling professional and medical help would relive the individuals from the drug and alcohol abuse. IV. Sports persons often misuse drugs to enhance their performance. (a) I and II (c) I, II and III (b) II and IV (d) All of these III. Matching Type Questions Codes A (a) 1 (c) 2 B 2 1 C 3 3 D 4 4 A Column II (Causative organisms) Dysentery 1. Entamoeba histolytica B. Malignant malaria 2. Plasmodium falciparum C. Common cold 3. Rhinovirus D. Ringworm 4. Trichophyton Codes A (a) 1 (c) 3 B 2 4 C 3 1 D 4 2 A (b) 2 (d) 4 B 3 1 C 4 2 D 1 3 Column II Haemophilus influenzae 1. Malignant malaria B. Entamoeba histolytica 2. Elephantiasis C. Plasmodium falciparum 3. Pneumonia D. Wuchereria bancrofti 4. Typhoid E. Salmonella typhi 5. Amoebiasis B 5 5 1 3 C 3 1 3 2 D 2 2 4 5 E 4 4 2 4 200 Match the diseases in Column I with the appropriate Column I Column II A. Active natural immunity 1. Injection of gamma globulins B. First line of defence 2. Complement proteins and interferons C. Passive natural immunity 3. Direct contact with the pathogens that have entered inside the body D. Second line of defence 4. Surface barriers 5. Antibodies transferred through the placenta Codes A (a) 4 (c) 3 B 3 4 C 5 5 D 2 2 A (b) 3 (d) 5 B 4 3 C 2 2 D 5 1 Chemical agent 1. Benzopyrene in cigarette smoke B. Physical agent 2. X-rays C. Biological agent 3. Oncogenic viruses Codes A (a) 1 (c) 3 B 2 1 C 3 2 A (b) 3 (d) 1 Amoebiasis 1. Treponema pallidum B. Diphtheria 2. Use only sterilised food and water C. Cholera 3. DPT vaccine D. Syphilis 4. Use of oral rehydration therapy B 2 3 C 1 2 203 Match the following columns. Column I (Biomedical techniques) Column II (Features) A. Biopsy 1. B. Radiography 2. Leukaemia C. Blood or Bone marrow test 3. X-rays are used to detect cancer of the internal organs D. Computed tomography 4. A piece of the suspected tissue cut into thin sections, stained and examined under Column II A. Column II (Examples) A. items (pathogen/prevention/treatment) in Column II. Column I D 3 1 Column II lists the corresponding descriptions. Match the two column, choose the correct option from those given. Column I (Cancer causing agents) A. Codes A (a) 1 (b) 3 (c) 5 (d) 1 C 1 4 202 Match the following columns. 199 Match the causative organisms with their diseases. Column I B 4 3 201 Column I lists the components of body defence and 198 Match the following columns. Column I (Diseases) A (b) 2 (d) 2 Uses X-rays to generate a three- dimentional image of the internals of an object microscope Codes A (a) 4 (c) 3 B 2 2 C 1 1 D 3 4 A (b) 4 (d) 2 B 3 1 C 2 4 D 1 3 www.mediit.in Master The NCERT > Biology (Vol-II ) 210 NCERT & NCERT Exemplar MULTIPLE CHOICE QUESTIONS NCERT 211 Diseases are broadly grouped into infectious and 204 Which one of the following diseases causes dry, scaly lesions on skin, nails and scalp? (a) Ringworm disease (c) Botulism (b) Skin allergy (d) None of these 205 Which one of the following pairs of diseases are viral as well as transmitted by mosquitoes? (a) (b) (c) (d) (d) II and IV (b) ESR test (d) Widal test 213 Many diseases can be diagnosed by observing the use of highly effective vaccine immunisation programmes elimination of animal reservoir international cooperation NCERT Exemplar 207 The term ‘Health’ is defined in many ways. The most accurate definition of the health would be (a) health is the state of body and mind in a balanced condition (b) health is the reflection of a smiling face (c) health is a state of complete physical, mental and social well-being (d) health is the symbol of economic prosperity 208 Transplantation of tissues/organs fails often due to the non-acceptance by the patient’s body. Which type of immune-response is responsible for such rejections? NEET 2018 Autoimmune response Cell-mediated immune response Hormonal immune response Physiological immune response 209 When an apparently healthy person is diagnosed as unhealthy by a psychiatrist, the reason could be that (a) the patient was not efficient at his work (b) the patient was not economically prosperous (c) the patient shows behavioural and social maladjustment (d) he does not take interest in sports 210 The organisms which cause diseases in plants and symptoms in the patient. Which group of symptoms are indicative of pneumonia? (a) Difficulty in respiration, fever, chills, cough and headache (b) Constipation, abdominal pain, cramps and blood clots (c) Nasal congestion and discharge, cough, sore throat and headache (d) High fever, weakness, stomach pain, loss of appetite and constipation 214 The disease chikungunya is transmitted by (a) house flies (c) cockroach (b) Aedes mosquitoes (d) female Anopheles 215 The sporozoites that cause infection when a female Anopheles mosquito bites a person, are found in (a) liver of the person (b) RBCs of mosquito (c) salivary glands of mosquito (d) gut of masquito 216 A person with sickle-cell anaemia is (a) more prone to malaria (b) more prone to typhoid (c) less prone to malaria (d) less prone to typhoid 217 Haemozoin is a (a) precursor of haemoglobin (b) toxin released from Streptococcus infected cells (c) toxin released from Plasmodium infected cells (d) toxin released from Haemophilus infected cells 218 Which of the following is not the causal organism for ringworm? (a) Microsporum (c) Epidermophyton (b) Trichophyton (d) Macrosporum 219 The substance produced by a cell in viral infection that can protect other cells from further infection is animals are called (a) pathogens (c) insects (b) II and III (c) III and IV (a) ELISA test (c) PCR test following facts except (a) (b) (c) (d) Codes (a) I and II 212 The clinical test that is used for diagnosis of typhoid is Elephantiasis and dengue Malaria and yellow fever Ringworm and dengue Yellow fever and dengue 206 Eradication of smallpox has been possible due to the (a) (b) (c) (d) non-infectious diseases. In the list given below, identify the infectious diseases. I. Cancer II. Influenza III. Allergy IV. Smallpox (b) vectors (d) worms (a) serotonin (c) interferon (b) colostrum (d) histamine www.mediit.in 211 CHAPTER 08 > Human Health and Diseases 225 AIDS is caused by HIV. Among the following, which 220 Antibodies present in colostrum which protect the newborn from certain diseases is of one is not a mode of transmission of HIV? (a) IgG type (c) IgD type (a) Transfusion of contaminated blood (b) Sharing the infected needles (c) Shaking hands with infected persons (d) Sexual contact with infected persons (b) IgA type (d) IgE type 221 Antivenom against snake poison contains (a) antigens (c) antibodies (b) antigen-antibody complexes (d) enzymes 226 The genes causing cancer are (a) structural genes (b) expressor genes (c) oncogenes (d) regulatory genes 222 Which of the following are the reasons for rheumatoid arthritis? I. The ability to differentiate pathogens or foreign molecules from self cells increases. II. Body attacks self cells. III. More antibodies are produced in the body. IV. The ability to differentiate pathogens or foreign molecules from self cells is lost. Choose the correct option. (a) I and II (c) III and IV 227 In malignant tumours, the cells proliferate, grow rapidly and move to other parts of the body to form new tumours. This stage of disease is called (a) metagenesis (c) teratogenesis 228 ‘Smack’ is a drug obtained from the (b) II and IV (d) I and III (a) latex of Papaver somniferum (b) leaves of Cannabis sativa (c) flowers of Datura pinata (d) fruits of Erythroxylum coca 223 Which of the following is not a secondary lymphoid tissue? (a) Spleen (b) Tonsils (c) Appendix (d) Thymus (b) metastasis (d) mitosis 229 Tobacco consumption is known to stimulate secretion 224 Which of the following glands is large sized at birth but reduces in size with ageing? of adrenaline and nor-adrenaline. The component causing this could be (a) Pineal (c) Thymus (a) nicotine (c) curcumin (b) Pituitary (d) Thyroid (b) tannic acid (d) catechin Answers Mastering NCERT with MCQs 1 (d) 16 (a) 31 (d) 46 (a) 61 (d) 76 (b) 91 (d) 106 (b) 121 (a) 136 (d) 151 (a) 2 (b) 17 (d) 32 (d) 47 (b) 62 (d) 77 (d) 92 (a) 107 (a) 122 (a) 137 (a) 152 (b) 3 (b) 18 (c) 33 (c) 48 (c) 63 (a) 78 (c) 93 (b) 108 (b) 123 (a) 138 (a) 153 (d) 4 (a) 19 (b) 34 (c) 49 (d) 64 (d) 79 (a) 94 (a) 109 (d) 124 (a) 139 (d) 154 (a) 5 (d) 20 (d) 35 (a) 50 (d) 65 (a) 80 (b) 95 (a) 110 (a) 125 (d) 140 (b) 155 (c) 6 (b) 21 (a) 36 (a) 51 (d) 66 (d) 81 (a) 96 (a) 111 (c) 126 (a) 141 (a) 156 (c) 7 (a) 22 (d) 37 (a) 52 (c) 67 (a) 82 (c) 97 (b) 112 (c) 127 (d) 142 (c) 157 (a) 8 (c) 23 (c) 38 (b) 53 (d) 68 (c) 83 (b) 98 (d) 113 (a) 128 (d) 143 (c) 158 (c) 9 (a) 24 (c) 39 (c) 54 (c) 69 (a) 84 (c) 99 (a) 114 (a) 129 (b) 144 (d) 159 (b) 10 (d) 25 (b) 40 (c) 55 (a) 70 (a) 85 (a) 100 (a) 115 (a) 130 (d) 145 (b) 160 (a) 11 (a) 26 (d) 41 (c) 56 (d) 71 (c) 86 (a) 101 (a) 116 (b) 131 (c) 146 (c) 161 (c) 12 (b) 27 (b) 42 (c) 57 (d) 72 (a) 87 (c) 102 (a) 117 (d) 132 (c) 147 (a) 162 (d) 13 (c) 28 (d) 43 (b) 58 (c) 73 (a) 88 (d) 103 (a) 118 (b) 133 (a) 148 (a) 14 (d) 29 (b) 44 (d) 59 (a) 74 (c) 89 (a) 104 (a) 119 (c) 134 (a) 149 (d) 15 (a) 30 (a) 45 (a) 60 (b) 75 (d) 90 (a) 105 (a) 120 (d) 135 (b) 150 (a) NEET Special Types Questions 163 (b) 164 (a) 165 (d) 166 (a) 167 (a) 168 (a) 169 (a) 170 (a) 171 (b) 172 (a) 173 (b) 174 (a) 175 (d) 176 (b) 177 (c) 178 (c) 179 (a) 180 (b) 181 (a) 182 (c) 183 (a) 184 (c) 185 (c) 186 (d) 187 (d) 188 (c) 189 (d) 190 (d) 191 (d) 192 (a) 193 (c) 194 (d) 195 (b) 196 (d) 197 (d) 198 (a) 199 (b) 200 (d) 201 (c) 202 (a) 203 (b) NCERT & NCERT Exemplar Questions 204 (a) 205 (d) 206 (c) 207 (c) 219 (c) 222 (b) 223 (d) 224 (c) 220 (b) 221 (c) 208 (b) 209 (c) 210 (a) 211 (d) 212 (d) 213 (a) 214 (b) 215 (c) 225 (c) 226 (c) 216 (c) 217 (c) 218 (d) 227 (b) 228 (a) 229 (a) www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 212 Answers & Explanations 6 (b) A disease, which can be easily transmitted from one 8 11 12 15 16 17 Answers & Explanations 18 20 21 22 person to another is called infectious disease. Infectious diseases are also known as transmissible disease or communicable disease. (c) Typhoid fever is caused by the bacterium Salmonella typhi and widal test is the confirmatory test for typhoid, which is based on antigen-antibody interaction. Typhoid fever or Enteric fever has the incubation period of 1 to 2 weeks. (a) Mary Mallon (nick named Typhoid Mary, born on September 23, 1869, Cookstown, Country Tyrone, Ireland). She was a cook by profession and was a famous typhoid carrier who allegedly gave rise to multiple outbreaks of typhoid fever through the food she prepared. (b) The correct option is (b) as Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsible for the disease pneumonia in humans, which infects the alveoli (air sacs) of the lungs. (a) Cholera and tetanus are diseases caused by bacteria. Cholera is caused by a bacterium Vibrio cholerae and tetanus is caused by a bacterium Clostridium tetani. Mumps, influenza, herpes and smallpox are viral diseases. Typhoid is a bacterial disease but, it is not paired with a bacterial disease. Hence, option (a) is correct. (a) Rhinoviruses represent one such group of viruses, which cause one of the most infectious human ailments– the common cold. (d) Pneumonia is caused by the bacteria Streptococcus pneumoniae and Haemophilus influenzae which infect the alveoli of lungs. On the other hand, common cold is caused by a variety of viruses, most commonly by rhinovirus (RNA virus) and affects the upper respiratory tract, but not the lungs. (c) HIV, hepatitis-B and ebola virus spread through direct contact between individuals. Direct transmission of vectors or disease occurs through sexual contact, exchange of body fluids like blood, semen, etc. Chikungunya is caused by the bite of Aedes aegypti mosquito, which requires no direct contact with body fluids like blood, semen or saliva for its transmission. (d) Different species of Plasmodium (P. vivax, P. malariae, P. falciparum and P. ovale) are responsible for causing different types of malaria. (a) Malignant malaria is caused by Plasmodium falciparum, which is the most serious type of malaria as it can even be fatal. (d) When an infected female Anopheles bites a healthy person, Plasmodium in the form of ‘sporozoites’ are transmitted from saliva of mosquito into the human body. Thus, one can look for the sporozoites of the malarial parasite in the saliva of the infected female Anopheles mosquito. 23 (c) Infective stage of Plasmodium for man is sporozoite. 24 26 30 32 33 Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The sporozoites mature into schizonts in the liver cells and releases merozoites upon rupture. These merozoites infect RBCs. Ookinete is the motile zygote of the parasite of the malarial mosquito that forms an oocyst in the mosquito’s gut. (c) Haemozoin is the toxic substance which is responsible for the high malarial fever. It is released due to the rupture of RBCs in the liver of human by the malarial parasite. (d) Female Anopheles is the primary host of the malarial parasite (Plasmodium). It is called primary host, as it serves as the place where Plasmodium lives and reproduces sexually. Human is called the secondary host of Plasmodium. (a) Entamoeba histolytica causes amoebiasis. It is a parasite of the large intestine of humans and is commonly contracted by ingesting contaminated water or food. (d) Malaria, amoebiasis and sleeping sickness all are protozoan diseases caused by the species of the protozoan Plasmodium, Amoeba and Trypanosoma, respectively. (c) Babesiosis is a malaria-like parasitic disease caused by infection with Babesia bigemina, a genus of protozoan piroplasms. The diseases in the other options and their causative agents are as follows Syphilis — Influenza — Blastomycosis — Treponema pallidum (bacterium) Influenza virus Blastomyces dermatitidis (fungus) 34 (c) Trichinella spiralis, a nematode parasite copulates in the intestine, after which males dies and females produce larvae which enter into the blood circulation to reach the muscles. The production of larvae indicates vivipary. Ancylostoma, Enterobius and Ascaris are all egg laying endoparasites. 35 (a) Ascariasis is caused by an intestinal endoparasite of human, ‘Ascaris lumbricoides,’ commonly called roundworm. Filariasis is caused by filarial worms, Wuchereria bancrofti and Wuchereria malayi. Both of these causative agents are helminths. 36 (a) Symptoms of ascariasis includes internal bleeding, muscular pain, fever, anaemia and blockage of the intestinal passage. Ascariasis is caused by an endoparasite of human, Ascaris lumbricoides commonly called roundworm. 37 (a) Infection of Ascaris occurs in a healthy person due to the drinking of water contaminated with eggs of Ascaris, vegetables (raw or uncooked), fruits, etc. www.mediit.in 40 (c) The filariasis pathogens are transmitted to a healthy 59 (a) Interferon is a suitable example of cytokine barrier. person through the bite of female of the pathogen mosquito Culex vectors. Which also serves as intermediate host. 42 (c) Elephantiasis is a helminthic disease caused by Wuchereria bancrofti and W. malayi. The infestation is transmitted by female Culex mosquitoes from one individual to the others. The worms live in the lymphatic system and slowly develops chronic inflammation. For the other options These are the proteins secreted by virus-infected cells and protect non-infected cells from further viral infection. (d) Interferon (a kind of protein) is a polypeptide produced by a T-cell infected with a virus that diffuses to surrounding cells and stimulates them to manufacture biochemicals that hinder viral replication. Thus, interferons can be used to encounter diseases caused by virus, i.e. hepatitis and common cold. (d) Interferons block viral reproduction in healthy cells and measles is caused by the measles virus.Thus, a person will develop interferons in his body, for the infection of measles. (a) Option (a) represents the cells involved in second line of defence. The second line of non-specific defence is primarily dependent upon neutrophils and macrophages, phagocytic white cells (phagocytes) in blood and lymph. Second line of defence also includes the functioning of interferons and the proteins of the complement system. (d) Option (a) and (b) both are correct as Antibodies are proteins produced in our body in response to antigens (pathogens). Antibody molecule specifically interacts with an antigen to produce an immune response. These are secreted by the action of both B-lymphocytes and T-lymphocytes. (c) IgG is the most abundant class of immunoglobulins in the human body. IgA, IgM, IgE, IgG, etc., are some of the different types of structurally related proteins (immunoglobulins) that act as antibodies. (a) Humoral immunity is also called as antibody mediated immunity. It refers to immunity provided by substances in the body fluid. Since, antibodies are found in the blood, therefore antibody mediated immunity is also referred to as humoral immunity. (a) Humoral immunity consists of antibodies in the blood and lymph. B-lymphocytes secrete antibodies. Thus, humoral immunity is mediated by B-cells or B-lymphocytes. (a) The cell-mediated immunity is one of the type of acquired immunity of human body which is carried out by the T-lymphocytes. (c) Cell-mediated immune response is responsible for the rejection of kidney graft. It is conferred by sensitised T-lymphocytes and here, antibodies are not produced. T-cells confer a long term memory and are able to discriminate between self and non-self. These cells sometimes consider graft as non-self and attack it, which causes its rejection. (d) Active immunity is an immunity, which is gained after natural infection and on exposure to live pathogens. In this type of immunity, the body produces antibodies as a response to specific pathogens or antigens. (b) Active immunity development is related to memory cells formed when B-cells and T-cells are activated by a l l l Ringworm is a fungal skin disease. Ascariasis pathogen affects small intestine of human beings. Amoebiasis pathogen affects the large intestine of humans. 61 62 63 43 (b) Pair in option (b) is not correctly matched and can be corrected as Syphilis is caused by bacteria Trypanosoma pallidum. Rest of the other pairs show correct match. 44 (d) The group of diseases carried (transmitted) by insects are 64 Malaria transmitted by by Anopheles mosquito (female). Filariasis transmitted by by Culex (female). Yellow fever transmitted by Aedes (female). 46 (a) Fungi parasitic on the skin, usually belong to the 47 49 51 56 57 58 genera of Microsporum, Epidermophyton or Trichophyton. Such fungi are responsible for ringworm infection and are also called cutaneous fungus. (b) Ringworm is an infectious disease. It is a skin infection caused by a fungus that can affect the scalp, skin, fingers, toes, nails or foot. (d) Gambusia is a fish which can control mosquito borne diseases like dengue, chikungunya, malaria, etc. These fishes feeds on larvae and pupae of certain mosquitoes and help in eradication of various insect borne diseases. (d) Innate immunity is also known as inborn/familiar/natural or genetic immunity. Innate immunity is the non-specific type of defence that is present in an individual at the time of birth. (d) The major phagocytic cells are macrophages. These cells perform phagocytosis, i.e. the process of engulfing a solid particle by a phagocyte. (d) Option (d) is correct as Cellular barrier of the body includes certain types of leucocytes (WBC) of the body like Poly Morpho-Nuclear Leucocytes (PMNL-neutrophils) . Monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues which can phagocytose and destroy microbes. (c) Innate immunity is the non-specific type of defence that is present at the time of birth because it has natural killer cells which can phagocytose and destroy microbes (cellular barriers). Other forms of innate immunity are physical, physiological and cytokine barriers. 68 69 70 72 74 75 76 Answers & Explanations 213 CHAPTER 08 > Human Health and Diseases www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 214 77 78 79 80 pathogen. These cells recognise the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies. (d) Passive immunity results when antibodies are directly given to an individual to protect the body against foreign agents. The acquisition of the antibodies in colostrum by an infant and the crossing of the placenta by maternal antibodies are examples of naturally acquird passive immunity. (c) Colostrum, the yellowish fluid, secreted by mother during the initial days of lactation is very essential to impart immunity to the newborn infants because it contains immunoglobulin-A. As IgA is secreted in mother’s milk, it is also called secretory immunoglobulin. (a) IgA antibody is involved in passive immunity. In this type of immunity, antibodies are directly given to protect the body against foreign agents. It is short lived. (b) Option (b) represents the correct information regarding antibodies. IgG antibody can cross placenta and provide natural passive immunity to the developing foetus. Other options are incorrect and can be corrected as follows l l l IgA is a dimer found in body secretions such as sweat, tears, saliva, mucus, colostrum , etc. It provides localised protections from pathogens. IgE is involved in hypersensitive reactions and presents in mast cells and basophill cells. IgM is found in pentamer form not as dimer. 81 (a) The principle of vaccination or immunisation is 82 Answers & Explanations 83 84 85 86 based on the property of memory of the immune system. The memory cells recognise the pathogen quickly and control the invaders by producing a large number of antibodies. (c) The pathogens used in vaccines are weakened and inactivated pathogenic agents. This stimulates the body to produce enough antibodies to protect against the disease. (b) Passive immunity refers to when antibodies are directly injected into the body to generate immune response. Thus, if a person is infected with some deadly microbes to which quick immune response is required as in tetanus, we directly inject the preformed antibodies or antitoxin into the body of the infected person. This is passive immunisation. (c) Oral polio vaccine consists of attenuated pathogens. Attenuated pathogens are living microorganisms or viruses cultured under adverse condition which leads to the loss of their virulance. But these organisms have the ability to induce lifelong immunity. The oral vaccine of polio contains three live polio strains in attenuated forms. (a) Human hepatitis-B virus vaccine was prepared by using antigen produced by recombinant strain of the yeast, Saccharomyces cerevisiae. (a) An allergen is any substance (antigen), most often eaten or inhaled, that is recognised by the immune system and causes an allergic reaction. 87 (c) IgE is an antibody which mediates allergic reactions. It plays a pivotal role in response to allergens such as anaphylactic drugs, bee stings, etc. They are synthesised by plasma cells and are found in only mammals. 88 (d) Allergens such as pollen grains, animal dander, dust, feathers, drugs like penicillin, etc., are non-infectious foreign substances, which induce allergic reaction in the body. 90 (a) For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens and the reactions displayed or observed. 92 (a) Asthma may be attributed to allergic reaction of the mast cells in the lungs. It is an allergic reaction characterised by spasm of bronchi muscles because of the effect of histamine released by mast cells in the lungs. 93 (b) In autoimmune disorder, the immune cells are unable to distinguish between self-cells and non-self cells and attack the self-cells. This occurs due to some genetic abnormality, e.g. rheumatoid arthritis. 94 (a) Myasthenia gravis is a chronic autoimmune neuromuscular disorder that causes fatigue, weakening and paralysis of skeletal muscles. In this, neuromuscular junctions are affected as the body produces antibodies which block the muscle from receiving signal from the nerve cells. 95 (a) Alzheimer’s disease is not an automimmune disease. It is caused due to the destruction of a large number of neurons in the hippocampus. It occurs due to a combination of genetic factors, environmental or lifestyle factors and the ageing process. In this, there is loss of neurotransmitter acetylcholine. Individuals with this disease have trouble remembering recent events. Rest all are autoimmune diseases. 97 (b) The primary lymphoid organs are bone marrow and thymus. The secondary lymphoid organs are spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix. 98 (d) Thymus provides the micro-environment for the development and maturation of T-lymphocytes. Thus, surgical removal of thymus of a newborn shall result in failure to produce T- lymphocytes. 99 (a) The thymus is a lobed gland located near the heart and beneath the breast bone, consisting mainly of lymphatic tissues and serving as the site of T-cell differentiation. 103 (a) MALT is Mucosal Associated Lymphoid Tissue located within the lining of the major tracts like respiratory, digestive and urinogenital tracts. It constitutes nearly 50% of the total lymphoid tissue in the human body. 105 (a) Human Immunodeficiency Virus (HIV) is a retrovirus (slowly replicating) that causes Acquired Immuno Deficiency Syndrome (AIDS). www.mediit.in 215 CHAPTER 08 > Human Health and Diseases 112 116 119 120 121 122 124 127 129 131 person infected by AIDS. This can be explained as after entering the body of a healthy person, the HIV enters into macrophages where RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase. (c) When HIV damages a large number of helper T-lymphocytes, the infected person starts showing symptoms of AIDS like bouts of fever, diarrhoea and weight loss. (b) In our body, cell growth and differentiation is highly controlled and regulated. But abnormal mitosis in an organ results in cancer. (c) The properties possessed by malignant tumour are uncontrolled cell division and metastasis, i.e. they do not remain confined in the area of formation and reach distant sites through blood, and wherever they get lodged in the body, these start the formation of a new tumour there. (d) Option (d) is not a property of cancerous cells. Contact inhibition involves major histocompatibility complex and is the natural process of arresting cell growth when two or more cells come in contact with each other. It is a property of normal cells. Cancer cells divide in uncontrolled manner and do not show contact inhibition. Remaining three are the properties of cancerous cells. (a) Transformation of normal cell into cancerous neoplastic cells is induced by carcinogens. These carcinogens can be physical, chemical or biological agents. (a) Physical carcinogens include a wide range of agents, e.g. ionising radiations like X-rays and γ-rays and non-ionising radiations like UV rays. These cause DNA damage leading to neoplastic transformation. (a) Tumour virus or cancer causing viruses are called oncogenic viruses. These viruses have oncogenes. An oncogene is a gene that has the potential to cause cancer. In tumour cells, these are often mutated or expressed at high levels. (d) Cancer cells show metastasis. Cancerous cells are actively dividing cells which starve the normal cells by competing for vital nutrients. These cancerous cells reach distant sites through blood and get lodged in the body and start a new tumours (masses of cells). This property of cancer cells is called metastasis. (b) Cancer is caused by loss of control over cell's reproductive capacity. They undergo rapid division and therefore, they are more easily damaged by radiations than normal cells. (c) Tumour cells have been shown to avoid detection and destruction by immune system. Therefore, the patients are given substances called biological response modifiers such as α-interferon, which activates their immune system and helps in destroying the tumours. 134 (a) The drug ‘heroin’ is synthesised by the acetylation 135 138 140 141 142 143 144 145 148 149 of morphine. Chemically heroin is diacetylmorphine and commonly it is called smack. It is an opium derivative which is used as a medicine. However, its excessive use causes addiction. (b) The latex of poppy plant (Papaver somniferum) is used to obtain ‘smack’. It is a white, crystalline, odourless, bitter compound, which acts as a depressant and slows down the body functions. (a) Natural cannabinoids are obtained from the leaves, resin and inflorescence of Cannabis sativa. (b) Cannabinoids such as ganja, charas, merijuana and hashish are effect cardiovascular system of the body. (a) Option (a) is correct. Fig A represents morphine a potent opiate analgesic drug that is used as sedative and to relieve severe pain. It is given to patients who have undergone surgery. It is taken by snorting and injection. The other options can be corrected as Fig B represents cannabinoids are known for its effect on cardiovascular system of the body. These are taken by inhalation and oral ingestion. (c) Coca alkaloid or cocaine is obtained from the coca plant Erythroxylum coca, native to South America. It is a natural stimulant and interferes with the transport of the neurotransmitter dopamine. (c) Cocaine, is commonly called coke or crack. It is usually snorted. Excessive dosage of cocaine causes hallucinations. (d) Traditionally, Erythroxylum (cocaine) was used to obtain anesthesia. It has an anesthetic and analgesic property which can alleviate the pain of headache, rheumatism, wounds and sores, etc. It was also used for broken bones, childbirth and during performing trepanning operations on the skull. (b) Cocaine is a potent stimulant drug as it directly affects the central nervous system by producing a sense of euphoria and increased energy. (a) The plant shown in the given picture is Datura, which produces natural hallucinogens. These drugs induce behavioural abnormalities by changing thoughts, feelings and perceptions without any actual sensory stimulus. (d) Drugs like barbiturates, amphetamines, benzodiazepines, Lysergic Acid Diethylamide (LSD) and other similar drugs, are normally used as medicines to help patients cope with mental illnesses like depression and insomnia. 150 (a) Lysergic Acid Diethylamide (LSD) is an extremely potent psychedelic ergot alkaloid derived from the fungus, Claviceps purpurea. LSD is one of the most powerful hallucinogenic drugs known. It was invented in 1938 by the Swiss chemist, Albert Hoffman, who was interested in developing medicines from compounds in ergot, a fungus that attacks rye. Answers & Explanations 111 (c) Macrophages are known as ‘HIV’ factory in a www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 216 151 (a) Option (a) shows the correctly matched pair of drug with its category. Others matching pairs are incorrect and can be corrected as l l l Lysergic acid diethylamide–Psychedelic drug. Heroin–Analgesic Benzodiazepines–Psychotropic drug. 152 (b) Amanita muscaria, is a fungus which is known for containing hallucinogenic (profound misinterpretation in a person’s perceptions of realty) properties. 153 (d) Nicotine is both an alkaloid and a steroid and it is 155 156 157 158 Answers & Explanations 159 161 162 extracted from the leaves of tobacco plant. An alkaloid is a nitrogenous organic compound of plant origin which has physiological actions on humans and steroids are synthetic drugs that closely resemble, cortisol, a hormone of adrenal gland. (c) Smoking addiction is harmful because smoke produces polycyclic aromatic hydrocarbons, currently classified as human carcinogens as these cause cancer. (c) Emphysema is a type of Chronic Obstructive Pulmonary Disease (COPD) involving damage to the air sacs (alveoli) in the lungs. (a) Benzopyrene is the carcinogen present in cigarette smoke. It is a polycyclic aromatic hydrocarbon formed as a result of incomplete combustion of organic matter such as coal, tar, tobacco, etc. It is a potential carcinogenic compound listed as Group 1 carcinogen by the IARC or International Agency for Research on Cancer. It reacts and binds to DNA, resulting in mutation and eventually leads to cancer. (c) Those who take drugs intravenously (direct injection into the vein using a needle and syringe), are much more likely to acquire serious infections like AIDS and hepatitis-B. This is because the viruses, which are responsible for these diseases, are transferred from one person to another by sharing of infected needles and syringes. (b) Cirrhosis of liver is caused by chronic intake of alcohol, which may be fatal for an individual. On intake, a part of alcohol is changed to acetaldehyde which causes hangover. Acetaldehyde stimulates formation of fat which is deposited on artery walls (causing coronary ailments) and in the liver (causing fatty liver syndrome). Gradually, the liver hardens and dries up as its cells are replaced by fibrous tissue. This kind of liver degeneration is called liver cirrhosis (Laennec’s cirrhosis). Excessive use of alcohol may also lead to liver failure, liver cell carcinoma, etc. (c) Cerebrum is involved in the loss of control over speech when a person consumes excessive alcohol. It attacks Broca’s area which is related to speech production. When a person consumes alcohol, it interfers with the brain’s communication pathways and thus, affects the brain’s information processing system and speech. (d) Option (d) is correct. The side effects of the use of anabolic steroids in females include masculinisation (features like males), increased aggressiveness, mood 163 164 165 166 167 168 swings, depression, abnormal menstrual cycles, excessive hair growth on the face and body, enlargement of clitoris, deepening of voice. In males, the side effects include acne, increased aggressiveness, mood swings, depression and reduction of size of the testicles, decreased sperm production, potential for kidney and liver dysfunction, breast enlargement, premature baldness, enlargement of the prostate gland. These effects may be permanent with prolonged use. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Shigella sp., Salmonella sp. and Escherichia coli are quite closely related genera of pathogenic bacteria that are responsible for diarrhoeal diseases. Dehydration is common symptom to all types of diarrhoeal diseases and adequate supply of fluids and electrolytes that provide ions, should be ensured. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Virus infected cells secrete proteins called interferons, which protect non-infected cells from further viral infection. (d) Assertion is false, but Reason is true. Assertion can be corrected as Interferon is a glycoprotein, production of which is induced within viral infected cells. Interferon induces an antiviral state within adjacent cells by interfering with viral replication. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Antibody mediated immune response occurs due to antibodies produced in the blood. These antibodies are chiefly secreted by B-cells into the body fluids. When an antigen (pathogen) enters the body the B-cells produce antibodies (immunoglobulins) in response to it. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Tetanus is bacterial disease which is caused by an exotoxin produced by Clostridium tetani. The wound anoxic conditions allows the germination of endospores and growth of the microorganism. So, a person with a bleeding wound needs anti-tetanus treatment. Anti-tetanus injection or antitoxin is a preparation of modified bacterical toxin that has been made non-toxic, but retains the capacity to stimulate the formation of antitoxins. It is usaually made in horses. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens (antigens). Allergens in the environment on reaching human body stimulate mast cells, which release excessive amount of chemicals like histamine. These chemicals www.mediit.in 217 CHAPTER 08 > Human Health and Diseases 170 171 172 173 174 175 with alcohol. Thus, athletes undergo dope test major tournaments or a match. 176 (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Repeated use of drugs, increase the tolerance level of receptors in our body because consumption or use of drugs for a longer period of time increases the number of receptors at neural junction which inturn, increases the tolerance level. Consequently, receptors respond only to higher doses of drugs thereby causing addiction. 177 (c) Assertion is true, but Reason is false. Reason can be corrected as Pork does not contain hexacanth larva as it gets converted into cysticercus form in the voluntary muscles of the pig. Humans get Taenia infection through direct or oral means. It occurs by eating raw or undercooked measly pork (pig muscle with cysticercus larvae of Taenia). Infection in vegetarians occurs through improperly washed vegetables. So, proper cooking of pork and properly washed vegetables can help to avoid Taenia infection. 179 (a) The statement in option (a) is correct with respect to immunity. Rest of the statements are incorrect and can be corrected as l l l The antibodies against smallpox pathogen are produced by memory cell is B-lymphocytes. Antibody is a protein molecule having two light chains and two heavy chains. Rejection of kidney graft is the function of T-lymphocytes. 180 (b) The statement in option (b) is correct. Rest of the statements are incorrect and can be corrected as l l HIV is an enveloped retrovirus. HIV escapes the immune cells and attacks helper T-cells of immune system. 182 (c) Statements I, III and V are correct. Statements II and IV are incorrect and can be corrected as l l Acquired immunity is not present from the birth and develops during an individual’s lifetime. It is pathogen specific. Thus, it is called specific immunity. Innate immunity is non-specific immunity. 183 (a) Statements I, II and III are correct, but statement IV is incorrect and can be corrected as l Dengue and chikungunya both are spread by Aedes mosquitoes. 193 (c) Statements I, III and IV are correct, but statement II is incorrect. It can be corrected as Allergic tendency can be genetically passed from the parents to their offspring and is characterised by the presence of large quantities of IgE antibodies in the blood. 204 (a) Ringworm disease causes symptoms like dry, scaly and lesions on skin, nails and scalp. These lesions also are also accompanied by intense itching. Answers & Explanations 169 cause marked dilation of all the peripheral blood vessels and the capillaries become highly permeable, so that large amounts of fluid leak out from the blood into the tissues thereby causing allergy. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Gymnosperms like Pinus usually grow on the slopes of hills and form dense forests of evergreen trees. The pollination of these plants takes place through wind and during peak hours, the microspore of Pinus are liberated as clouds of yellow dust (sulphur shower). On inhalation, these microspores (pollens) cause various allergies like dermatitis, asthma, allergic rhinitis, hay fever, etc., in human beings. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. HIV or Human Immunodeficiency Virus is the causative agent of AIDS. AIDS arises due to the deficiency of the immune system acquired during the life time of a host. HIV causes AIDS by damaging the immune system of the human body. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Cancer is caused by damage to genes regulation of the cell division cycle. It is an uncontrolled proliferation of the cells. These cancerous cells become immortal because of the breakdown of the cell growth and differentiation regulatory mechanisms and the loss of a property called contact inhibition. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Metastasis is the phenomenon in which tumour cells detach and migrate to other parts of the body where they give rise to secondary tumours (i.e. masses of cells produced at different locations in the body). Metastasis is the property of cancerous cells, which have abnormal antigens on their surface and unusual number of chromosome in their nucleus thereby causing metastasis. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Cannabinoids are chemicals known for their effects on cardiovascular system of the body, as these increase the heart rate, blood pressure, etc. Cannabinoids interact with cannabinoid receptors present in the brain and cause hallucinogenic effects. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. High alcohol consumption is harmful during pregnancy. This is because Foetal Alcohol Syndrome (FAS) is the name given to a group of physical and mental defects caused by foetal exposure to alcohol in the womb. (d) Assertion is false, but Reason is true. Assertion can be corrected as Dope test is the blood test used to estimate whether a person taking part in a competition used any drug to make their performance better. Dope test is not related www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 218 206 (c) Option (c) is incorrect and can be corrected as 208 209 210 211 213 Animal reservoir of the smallpox does not exist. Rest all options contain facts which led to smallpox eradication. (b) Transplantation of tissue/organs may fail, when that tissue is rejected by the recipient’s immune system leading to its destruction. Tissue rejection is a function of cell-mediated immune response that involves T-cells.These cells have the ability to distinguish between self and nonself cells. After the recognition of non-self tissue the killer T-cells induces apoptosis of the target tissue. (c) Health can be defined as a state of complete physical, mental and social well-being. So, when an apparently healthy person is diagnosed as unhealthy by a psychiatrist, the reason could be that the patient shows behavioural and social maladjustment due to the mental discomfort. (a) A wide range of organisms including bacteria, viruses, fungi, protozoans, helminths, etc., cause diseases in plants and animals. Such disease causing organisms are called pathogens. On the other hand, vectors are the carriers of pathogens which may be insects or worms. (d) Influenza (commonly known as the ‘flu’) and smallpox are infectious diseases.These diseases can get transmitted from an unhealthy person to a healthy person by physical means diseases. Whereas, cancer and allergy are non-infectious and non-transferable disease. (a) Option (a) represents the group of symptoms which are indicative of pneumonia. Rest of the symptoms and their respective diseases are given below l l l Constipation, abdominal pain, cramps and blood clots indicate amoebiasis. Nasal congestion and discharge, cough, sore throat and headache indicate common cold influenza. High fever, weakness, stomach pain, loss of appetite and constipation indicate typhoid. Answers & Explanations 215 (c) Sporozoites enter the female Anopheles mosquito when they bite an infected person where these sporozoites fertilise and multiply in the stomach wall of the female Anopheles. These then get stored in the salivary glands of the mosquito till it is again transferred to the human body by a mosquito bite. 216 (c) People suffering from sickle-cell anaemia are less prone to malarial parasite as RBC of sickle-cell anaemic patients is distorted in shape. The membrane of the sickle-cells are stretched due to their distorted shape and thus, become porous. The cells leak all the nutrients needed by the parasite to survive and the faulty cells along with the parasite eventually get eliminated. 217 (c) Haemozoin is a toxin released by Plasmodium infected cells. This substance is responsible for producing chills and high fever recurring every three to four days. 218 (d) Ringworm infections are caused by fungi belonging to the genera–Microsporum, Trichophyton and Epidermophyton. Macrosporum is not a causal organism for ringworm. 219 (c) The cytokine-barriers include interferons. These 220 221 222 223 224 225 226 228 229 are the proteins secreted by virus infected cells, which protect non-infected cells from further viral infection. (b) The yellowish fluid colostrum secreted by mother during the initial days of lactation, has abundant antibodies (IgA) to protect the infant from several diseases during the initial six months. (c) Antivenom against snake poison contains antibodies. It is a biological product that typically consists of venom neutralising antibodies derived from a host animal, such as a horse or sheep. It is not considered as antigen or antigen-antibody complex or enzyme. (b) Statements II and IV show the correct reasons for rheumatoid arthritis. It is an autoimmune disorder. Autoimmunity is an abnormal immune response in which the immune system of the body starts rejecting its own body cells or ‘self’ cells and molecules. This happens as the body loses its ability to differentiate the pathogen or foreign molecules from self cell and attacks self-cells damaging them. (d) Thymus is not a secondary lymphoid tissue rather it is a primary lymphoid organ in which origin and/or maturation and proliferation of lymphocytes occur. The secondary lymphoid organs such as spleen, tonsils, appendix, lymph nodes provide sites for interaction of lymphocytes with the antigen, which then proliferate to becomes effector cells. (c) The thymus is a lobed organ located near the heart and beneath the breastbone. The thymus is quite large at the time of birth but keeps on reducing in size with age and by the time puberty is attained it reduces to a very small size. (c) Shaking hands with infected people is not a mode of transmission of HIV. Rest of the other options all indicate different modes of HIV transmission. (c) The genes which cause cancer are called oncogenes. Normal cells have genes called cellular oncogenes or proto-oncogenes, which are present in inactivated state, but under certain conditions (like mutation) these get transformed to cancer causing oncogenes. (a) ‘Smack’ is obtained by acetylation of morphine, extracted from the latex of poppy plant (Papaver somniferum). Smack (also called heroin) is chemically diacetyl morphine and is a white, odourless, bitter, crystalline compound. (a) Tobacco has nicotine, which stimulates the adrenal gland to release adrenaline and nor-adrenaline which in turn increases the blood pressure and heart rate. For rest of the other options. Tannic acid is a type of polyphenol used as a modrant. l l Curcumin is a pain reliever. Catechin derived from catechu is an antioxidant. www.mediit.in CHAPTER > 09 Strategies for Enhancement in Food Production NEET KEY NOTES Animal Husbandry Å It is the agricultural practice of breeding and raising livestock like buffaloes, cows, pigs, horses, cattle, sheep, camel, goat, etc. Strict cleanliness and hygiene are important while milking, storage and transport of the milk and its products. Å Regulator inspections for stringent up keep and proper record maintenance. Å It includes poultry farming and fisheries. Å Regular visits by a doctor would be mandatory. Å Fisheries include rearing, catching, selling, of fish, molluscs (shell-fish) and crustaceans (prawns, crabs, etc). Poultry Farm Management Å More than 70% of worlds livestock population is in India and China. However, its contribution to the world farm produce is only 25%. Å Management of Farms and Farm Animals Å Poultry is the class of domesticated fowl (birds) used for food or their eggs. Å It mainly includes chicken and ducks and sometimes turkey and geese. Å Important components of poultry farm management include Practices employed to enhance food production from animals targeted management of farm and farm animals such as dairy farm management and poultry farm management. Dairy Farm Management Å Dairying is the management of animals for its milk and its product for human consumption. In dairy farm management, we deal with processes and systems that increase yield and improve quality of milk. Å Selection of good breeds having high yielding potential, combined with resistance to diseases is very important. Å Cattles have to be housed well, should have proper water and be maintained disease free. Å The feeding of cattle should be carried out in a scientific manner (quality and quantity of fodder). Å n Selection of disease free and suitable breeds n Proper and safe farm condition n Proper feed and water n Hygiene and healthcare A viral infection affecting poultry birds is bird flu. It is caused by infection with bird flu virus or H5 N1 virus. It is deadly to birds and can easily affect humans through consumption of their products (eggs, meat, etc) and other animals that come in contact with a carrier. Animal Breeding Å It aims at increasing yields of animals and improving the desirable qualities of the product. Å A breed is a group of animals related by descent and similar in most of characters like general appearance, features, size, configuration, etc. www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 220 Å There are two kinds of breeding, i.e. inbreeding (breeding between same breeds) or outbreeding (breeding between different breeds). Inbreeding Å Å Å Å Outbreeding Method of mating of more closely related individuals within the same breed, i.e. superior males and superior females of the same breed for 4-6 generations. Method of mating of unrelated animals for 4-6 generations. It is of three types, i.e. outcrossing, cross-breeding and interspecific hybridisation. Advantages It increases homozygosity, so it is used for developing purelines. It exposes harmful recessive genes that are eleminated by selection. It also helps in accumulation of superior genes and elimination of less desirable genes. Advantages It produces hybrids with desirable characters of both the parents like better lactation period and high milk productions. Continued inbreeding reduces fertility and even productivity. This is called inbreeding depression. Whenever this becomes a problem. Selected animals of the breeding population should be mated with unrelated superior animals of the same breed. This usually helps to restore fertility and yield. Outcrossing is the mating of animals within same breed but having no common ancestors up to 4-6 generations. The offspring are called outcross. This method helps in increasing the milk production, growth rate in beef cattle etc. Cross-breeding is the mating of superior male of one breed with the superior female of another breed. The progeny formed by this, may themselves be used for the commercial production or alternatively used to develop new superior breeds. The genetic mother becomes available for another round of superovulation. High milk-yielding breeds of females and high quality (lean meat with less lipid) meat- yielding bulls have been bred successfully this technique to increases a herd size in short time. Bee-keeping Å A remarkable growth in the practice of bee-keeping or apiculture has been observed as it is a old cottage industry requiring less manpower and management skills. Also,demand for its products honey (high nutritive value and indigenous medicine) and beeswax (used in the preparation of cosmetics and polishes) has increased significantly. Å Bee-keeping can be practiced in any area where sufficient pasture is available. The most common species of honybee is Apis indica. Å Few points are important for successful bee-keeping like-knowledge of the nature and habits of bees, selection of suitable location for beehives, catching and hiving of swarms, management of beehives during different seasons and proper handling and collection of honey and beeswax. Fisheries Å Fishery is another flourishing industry meeting the ever-increasing demand for fish, fish products and other aquatic foods. It includes catching, processing and marketing of fishes. Å Freshwater fishes which are very common include catla, rohu and common carp. Common marine fishes are hilsa, sardines, mackerel and pomfrets and selling of fish, shellfish and other aquatic animals. Å By this technique, Hisardale (a new breed of sheep) developed in Punjab by crossing Bikaneri ewes and Marino rams. Å Å Interspecific hybridisation is the mating of male and female animals of two different related species. The progeny may be of considerable economic value, e.g. mule. Å This industry provides employment to millions of fisherman and farmers particularly in the coastal states. Å Different techniques have been applied to increase the production of aquatic plants and animals such as aquaculture and pisciculture. Å Blue revolution is implemented to increase fish production. Å Å Å To improve the chances of successful production of hybrids, controlled breeding methods such as MOET (Multiple Ovulation Embryo Transfer) technique and artificial insemination are applied. These methods have given better results than the conventional selective hybridisation. In artificial insemination, the semen is collected from the male and injected into the reproductive tract of the selected female. In this way, desirable matings are carried and it helps us to overcome several problems of normal matings. In MOET, cow is administered with FSH hormone, to induce follicular maturation and superovulation and instead of 1, they produce 6-8 eggs. After mating, all these fertilised eggs at 8-32 cell stage are collected and transferred to surrogate mothers. NEET Plant Breeding Å India‘s economy is based on agriculture and nearly 62% of the population is employed in this sector at various levels. As only limited land is fit for cultivation, India has to strive to increase yields per unit area from existing farm lands. Å Plant breeding techniques led to a dramatic increase in food production in 1960. This is often referred to as the green revolution. KEY NOTES www.mediit.in 221 CHAPTER 09 > Strategies for Enhancement in Food Production What is Plant Breeding? n n Å Plant breeding involves purposeful manipulation of plant species used to create varieties, which have increased crop yield, improved quality, increased tolerance to environmental stresses (extreme temperatures, salinity, drought), resistant to pathogens and to insect pests. Eventually, achieving the goal of increase in the yield of the food. Å Plant breeding programmes are carried out in a systematic way. The main steps in plant breeding are 1. Collection of variability is the collection and preservation of all the different wild varieties, species and relatives of the cultivated species. The entire collection of plants or seeds having all the diverse alleles for all genes in a given crop is called germplasm collection. 2. Evaluation and selection of parents is the identification of plants with desirable characteristics. The selected plants are multiplied and used in hybridisation process. 3. Cross hybridisation among the selected parents to obtain desired crop characters, e.g. high protein quality of one parent combined with disease resistance from another parent. This is possible by cross hybidising the two parents to produce hybrids that have genetically combined characters in one plant. 4. Selection and testing of superior recombinants is the selection of the plant having desired character combination. This step requires scientific evaluation of the progeny and yield plants that are superior to both of the parents. These are self- pollinated for several generations till they become uniform or homozyous. 5. Testing, release and commercialisation of new cultivars The newly selected lines are evaluated for their yield and other agronomic traits (of quality, disease resistance, etc.) by growing these in the research fields and recording their performance under ideal fertiliser application, irrigation and other crop management practices. Final step involves testing the generated varieties in farmer’s fields, for at least three growing seasons, at several locations in the country, representing all the agroclimatic zones, where the crop is usually grown. Å Hybrid varieties of crop plants, developed in India are n n Wheat Varieties such as Sonalika and Kalyan Sona are high yielding and disease resistant.These were derived from semidwarf variety developed by Nobel laureate Norman E Borlaug, at International Centre for Wheat and Maize Improvement (CIMMYT) in Mexico. Rice Semidwarf rice varieties were derived from IR-8 [developed at International Rice Research Institute (IRRI), Philippines] and Taichung Native-1 (from Taiwan). Jaya and Ratna were developed in India. n n Sugarcane Saccharum barberi of North India had poor sugar content and yield. Tropical canes grown in South India Saccharum officinarum had thicker stems and higher sugar content but did not grow well in North India. These two species were crossed to get sugarcane varieties with high yield, thick stems, high sugar content and ability to grow in North India. Millets Hybrid varieties of maize, jowar and bajra that are high yielding and resistant to water stress have been developed in India. Plant Breeding for Disease Resistance Å Fungal, bacterial and viral infections in cultivated crop species reduce the crop yield up to 20-30%, especially in tropical climates. Å To reduce infections and to cut down the use of fungicides and bactericides, disease resistant varieties need to be developed. Å Resistance of the host plant is the ability to prevent the pathogen from causing disease and is determined by the genetic constitution of the host plant. Some of the diseases caused by various pathogens are n Fungi Brown rust of wheat, red rot of sugarcane and late blight of potato. n Bacteria Black rot of crucifers. n Viruses Tobacco mosaic, turnip mosaic, etc. Methods of Breeding for Disease Resistance Å Conventional breeding The steps are Screening germplasm for resistance sources. Hybridisation of selected parents. Selection and evaluation of the hybrids. Testing and release of new varieties. Some Important Varieties Developed by Conventional Breeding n n n n Crop Variety Resistance to diseases Wheat Himgiri Leaf and stripe rust, hill bunt Brassica Pusa Swarnim (Karan rai) White rust Cauliflower Pusa Shubhra, Pusa Snowball K-1 Black rot and curl blight black rot Cowpea Pusa Komal Bacterial blight Chilli Pusa Sadabahar Chilli mosaic virus, Tobacco mosaic virus and leaf curl. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 222 Å Mutation breeding is the process of breeding by artificially inducing mutations using chemicals or radiations (gamma radiations). Å Mutation is the process by which base sequence within genes changes, resulting in the creation of a new character or trait not found in the parent plant, e.g. n n Å The objective of breeding for improved nutritional quality is to improve n n n Å By using biofortification technique, we had developed In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations. n In bhindi (Abelmoschus esculentus), resistance to yellow mosaic virus was transferred from a wild species to the crop species by sexual hybridisation and a new variety of A. esculentus called Parbhani kranti was produced. n n Plant Breeding for Developing Resistance to Insect Pests n n Å Insect and pest infestations are another major cause for large scale destruction of crop plant and crop production. Insect resistance in host crop plants may be due to morphological, biochemical or physiological characteristics. n n Morphological pest deterrents Hairy leaves in several plants are associated with resistance to insect pests, e.g. resistance to jassids in cotton and cereal leaf beetle in wheat. Solid stems in wheat, is not preferred by the stem sawfly, smooth leaved and nectar less cotton varieties do not attract bollworms. Biochemical pest deterrents High aspartic acid, low nitrogen and sugar content in maize leads to resistance to maize stem borers. Breeding methods for insect pest resistance are same as for disease resistance. Sources of resistance genes may be cultivated varieties, germplasm collections of the crop or wild relatives. Some Crop Varieties Breed by Hybridisation and Selection, for Insect Pest Resistance Crop Variety Insect pests Brassica (rapeseed mustard) Pusa Gaurav Aphids Flat bean Pusa Sem 2 and Pusa Sem 3 Jassids, aphids and fruit borer Pusa Sawani and Pusa A-4 Shoot and fruit borer Okra (bhindi) n n Å More than 840 million peoples in the world do not have adequate food to meet their nutritional and daily food requirements and about these billion people suffer from micronutrient, protein and vitamin deficiencies, i.e. hidden hunger. Biofortification is the method of breeding crops with higher levels of vitamins, minerals and healthier fats to improve public healths. NEET Maize hybrids with twice the amount of the amino acids, lysine and tryptophan, compared to existing maize hybrids. Wheat variety, Atlas 66, having a high protein content. An iron-fortified rice variety with five times higher iron content than in commonly consumed varieties. Vitamin-A enriched carrots, spinach, pumpkin. Vitamin-C enriched bitter gourd, bathua, mustard, tomato. Iron and calcium enriched spinach and bathua. Protein enriched beans - broad, lablab, French and garden peas. The Indian Agricultural Research Institute, New Delhi has released above mentioned vegetable crops rich in vitamins and minerals. Single Cell Protein (SCP) Å It refers to the source of mixed proteins extracted from pure or mixed culture of organisms or cells. It acts as a supplement or alternative source of protein that is not supplied by the traditional of conventional agriculture production. Å Several microbes have also been used as source of good proteins. Microbes like Spirulina and Methylophilus methylotrophus are being grown on an industrial scale on materials like waste water from potato processing plants (containing starch), straw, molasses, animal manure and even sewage. Å Advantages of SCP n n Plant Breeding For Improved Food Quality Å protein and oil content and quality vitamin content. micronutrients and mineral content. Using waste as nutrient medium reduces environmental pollution. Because of their high rate of biomass production and growth, microbes can produce much bigger amount of protein than the larger animals, e.g. 250 gm of Methylophilus methylotrophus produces 25 tonnes of proteins. Tissue Culture Å As traditional breeding techniques were slow new technology called tissue culture was developed as a fast and efficient systems for crop improvement. Å Plants have a special property called totipotency which is the capacity to generate a whole plant from any cell. KEY NOTES www.mediit.in 223 CHAPTER 09 > Strategies for Enhancement in Food Production Å Plants can be regenerated in lab from explants, i.e. any part of a plant taken out and grown in a test tube, under sterile conditions in special nutrient media. Å The nutrient medium must provide, a carbon source such as sucrose, inorganic salts, vitamins, amino acids and growth regulators like auxins and cytokinins. Å Micropropagation is the method of producing thousands of plants through tissue culture. Each of these plants will be genetically identical to the original plant from which they were grown, i.e. they are somaclones. Many important food plants like tomato, banana, apple, etc., have been produced on commercial scale using this method. Å Å Another application of tissue culture method is the recovery of healthy plants from diseased plants. Even when the plant is infected with a virus, the meristem (apical and axillary) remains infection free; it can be removed, grown in vitro to obtain virus-free plants. Meristems of banana, sugarcane, potato, etc., have been isolated. Somatic hybridisation is the process of in vitro fusion of protoplasts of somatic cells obtained from different varieties or species of plants on a suitable nutrient medium to develop a hybrid. In this process, first the cell wall of plant cells are removed. The protoplasts of these cells are allowed of fuse in the presence of PEG. Later, the fused protoplasts develop thin own walls and are called as somatic hybrids, e.g. pomato. Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Animal Husbandry, Management of Farms and Farm Animals 1 …… is the agricultural practice of feeding, breeding 6 The management of animals for milk and its and raising livestock. Choose the most appropriate word to fill in the blank. products for human consumption is called (a) (b) (c) (d) Animal husbandry Cattle improvement Both (a) and (b) Cattle farming (b) poultry farming (d) All of these 3 Crustacean fishery is connected with exploitation of (a) (b) (c) (d) oysters and crabs mussels and squids shell and cuttle fish crabs and prawn 4 Livestock refers to (a) (b) (c) (d) pet animals poultry and pet animals domestic animals which are kept for use or profit None of the above 5 The practices concerned with the improvement in animal husbandry include (a) (b) (c) (d) (b) poultry farming (d) livestock improvement 7 In dairy farm management 2 Animal husbandry includes (a) fisheries (c) dairying (a) dairy farming (c) white revolution management of farm and farm animals management of animals and plants at a same place genetic engineering None of the above (a) (b) (c) (d) livestock improvement is done milk yield and quality is improved regular inspection of animals All of the above 8 Choose the correct option. (a) More than 70% of the world livestock population is in India and China (b) The contribution of India and china to the world farm produce is about 25% (c) Important livestock of India are cattle and buffaloes (d) All of the above 9 Which of the following qualities is considered for the selection of good breeds? (a) High yielding potential (c) Breed with pureline (b) Resistance to diseases (d) Both (a) and (b) 10 What measures should be taken for cattles, to realise the yield potential? (a) (b) (c) (d) They have to be housed well Feeding should be in scientific manner Hygienic milking, storage and transport of milk All of the above www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 224 11 Which of the following birds are domesticated in 14 poultry farm management? (a) Chicken (c) Turkey and geese (b) Ducks (d) All of these 12 Which of the following points should be kept into consideration for management of poultry farm? A. Selection of disease free and suitable breeds B. Proper and safe farm conditions C. Proper feed and water D. Hygiene and healthcare (a) A,B,C (b) A,C,D (c) A,B,C,D (d) None of these 13 Bird flu is a ………… disease. (a) viral (c) fungal (b) bacterial (d) algal Identify improved breed shown in diagram. (a) A–Jersey, B–Leghorn (b) A–Surti, B–Sangamneri (c) A–Marwari, B–Sirohi (d) A–Beetal, B–Jamunapari 15 An infectious bacterial disease of cattle, buffaloes, sheeps and goats is (a) anthrax (c) tick fever (b) rinderpest (d) necrosis TOPIC 2 ~ Animal Breeding, Bee-keeping and Fisheries 16 Which of the following is an aim of animal breeding? (a) (b) (c) (d) Increasing the yield of animals Improving the desirable qualities of the produce Producing better looking animals Both (a) and (b) 17 The term ‘breed’ refers to (a) a group of animals not related by descent but similar in most characteristics (b) a group of animals related by descent and similar in most characteristics (c) a group of animals related by descent but have almost different characteristics (d) a group of animals neither related by descent nor have similar characteristics 18 The term ‘inbreeding’ refers to (a) mating of more closely related individuals within the same breed for 4-6 generations (b) mating of unrelated animals of the same breed (c) mating of animals within the same breed, but having no common ancestors up to 4-6 generations (d) superior males of one breed are mated with superior females of another breed 19 A superior female, in the case of cattle is the …A… that produces more milk per lactation. On the other hand, a superior male is the …B…, which gives rise to …C… as compared to those of other males. Here, A to C refers to (a) (b) (c) (d) A–cow, B–bull, C–superior progeny A–buffalo, B–bull, C–inferior progeny A–cow, B–bull, C–inferior progeny A–cow, B–bull, C–normal progeny 20 Continued inbreeding (a) reduces fertility (b) reduces productivity (c) causes inbreeding depression (d) All of the above 21 Homozygous purelines in cattle can be obtained by NEET 2017 (a) mating of related individuals of same breed (b) mating of unrelated individuals of same breed (c) mating of indviduals of different breed (d) mating of individuals of different species 22 Suggest a way to overcome inbreeding depression. (a) Selected animals should be mated with related superior animals of different breed (b) Selected animals should be mated with unrelated superior animals of same breed (c) Selected animals should be mated with related superior animals of same breed (d) Selected animals should be mated with unrelated superior animals of different breed 23 Outbreeding is an important strategy of animal husbandry because it CBSE-AIPMT 2015 (a) helps in accumulation of superior genes (b) is useful in producing purelines of animals (c) is useful in overcoming inbreeding depression (d) exposes harmful recessive genes that are eliminated by selection 24 When breeding is between the unrelated animals, including individuals of the same breed but having no common ancestors for 4-6 generations or between different breeds or different species, is called (a) outbreeding (c) controlled breeding (b) inbreeding (d) hybridisation www.mediit.in 225 CHAPTER 09 > Strategies for Enhancement in Food Production 25 Hissardale is a new breed of …A… developed in Punjab by crossing …B… and …C… . Here A to C refers to (a) (b) (c) (d) A–sheep, B–Bikaneri ewes, C–Marino rams A–chicken, B–Dorking, C–Sussex A–chicken, B–Leghorn, C–Plymouth rock A–cow, B–Jersey, C–Brown Swiss 26 Interspecific hybridisation is the mating of NEET 2016 (a) animals within same breed without having common ancestors (b) two different related species (c) superior males and females of different breeds (d) more closely related individuals within same breed for 4-6 generations 33 Fill up the blanks. I. …… A ……refers to the cross of superior males of one breed with superior females of another breed. II. …… B …… is a method of controlled breeding in which semen from the selected male parent is injected into the reproductive tract of the selected female parent. III. …… C …… refers to crossing between male and female animals of two different species. IV. …… D …… is a programme for herd improvement in animals like cattle, sheep, buffaloes, etc. A (a) MOET 27 A mule is produced by (a) (b) (c) (d) cross-breeding outcrossing inbreeding interspecific hybridisation 28 Controlled breeding experiments are carried out using (a) interspecific hybridisation (b) artificial insemination (c) outcrossing (d) intraspecific hybridisation 29 MOET stands for (a) (b) (c) (d) Multiple Ovulation Embryo Transfer technology Multiple Ovary and Embryo Transfer technology Multiple Ovulation Embryo Test technology Method of Egg Transfer 30 In MOET procedure, to induce follicular maturation and superovulation which of the following hormones are administered to the cow? (a) Follicle stimulating hormone (b) Progesterone (c) Androgen (d) Oxytocin 31 During MOET at which of the following stages, embryo is transferred to surrogate mothers (a) (b) (c) (d) Unfertilised ovules 2-celled stage Fertilised egg 8-32 celled stage 32 In which of the following techniques high milk giving breeds of females and high quality meat giving bulls have been bred successfully to increase herd size short time? (a) (b) (c) (d) MOET Artificial insemination Interspecific hybridisation Induced mutation B C Interspecific Artificial hybridisation insemination (b) Cross-breeding Artificial Interspecific insemination hybridisation (c) Artificial insemination MOET (d) Interspecific hybridisation Artificial MOET insemination D Cross-breeding MOET Cross-breeding Interspecific hybridisation Cross-breeding 34 Rearing of honeybees for obtaining honey and beeswax is called (a) pisciculture (c) apiculture (b) sericulture (d) aquaculture 35 Most common honeybee species in India (a) Apis indica (c) Apis mellifera (b) Apis florea (d) Apis dorsata 36 Which of the following given point is important for successful bee-keeping? (a) Knowledge of the nature and habits of bees (b) Selection of suitable location for keeping the beehives (c) Catching and hiving of swarms (group of bees) and their management during different seasons (d) All of the above 37 Keeping beehives in crop field during flowering period (a) (b) (c) (d) improve honey and wax yield improves crop yield pollination efficiency All of the above 38 Name the industry that includes catching, processing or selling of aquatic animals. (a) Fisheries (c) Sericulture (b) Apiculture (d) None of these 39 Which of the following is not a freshwater fishes? (a) catla (c) common carp (b) rohu (d) mackerel www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 226 40 Edible fishes found in marine water habitat is/are (a) (b) (c) (d) 42 Which of the following activities has contributed towards increased production of aquatic organisms? sardines pomfrets Hilsa All of the above 41 Among the following edible fishes, which one is a marine fish having rich source of omega-3 fatty acids? NEET 2016 (a) Mystus (b) Magur (c) Mrigala (d) Mackerel (a) (b) (c) (d) Pisciculture and sericulture Pisciculture and aquaculture Pisciculture and blue revolution Blue and green revolution 43 The byproducts obtained from fisheries are (a) (b) (c) (d) isinglass, oil, shagreen and fishmeal eggs, meat, oil and leather isinglass and eggs None of the above TOPIC 3 ~ Plant Breeding and Single Cell Protein 44 Green revolution in India was possible due to (a) (b) (c) (d) exploitation of high yielding varieties intensive cultivation better irrigation, fertilisers and pesticide facilities All of the above 45 Green revolution depended mainly on plant breeding techniques for high yielding and disease resistant varieties in (a) wheat (b) rice (c) maize (d) All of these 46 ……… is the purposeful manipulation of plant species in order to create plant types that are better suited for cultivation, give better yield and are disease resistant. Fill up the blanks. (a) (b) (c) (d) Aquaculture Plant breeding Animal husbandry Apiculture 47 Following are the steps to produce a new genetic variety of crop. Collection of germplasm. ↓ A ↓ Cross-breeding /Hybridisation ↓ B ↓ Testing, release and commercialisation of the new cultivars Choose appropriate option for A and B. (a) A–Selection of parents; B–Testing of superior recombinants (b) A–Evaluation of parents; B–Selection of superior recombinants (c) A–Testing of parents; B–Selection of superior recombinants (d) A–Evaluation and selection of parents; B–Selection and testing of superior recombinants 48 Which of the following is considered as the root of any breeding programme? (a) (b) (c) (d) Genetic variability Cross hybridisation Hybrid vigour Heterosis 49 In plant breeding programmes, the entire collection (of plants/seeds) having all the diverse alleles for all NEET 2013 genes in a given crop is called (a) selection of superior recombinants (b) cross-hybridisation among the selected parents (c) evaluation and selection of parents (d) germplasm collection 50 Which of the following is the main aim of evaluation of germplasm in plant breeding programme? (a) To identify plants with desirable combination of characters (b) For effective exploitation of the natural genes (c) To look for harmful mutated gene (d) For collection of variability 51 In case of plant breeding, cross hybridisation is a time consuming and tedious process because (a) pre-existing genetic variability is collected from wild varieties, species and relatives of the cultivated crop species (b) it involves the selection of plants among the progeny of the hybrids with desired combination of characters (c) it involves emasculation and bagging techniques to transfer desired pollen grains to the stigma of desired plant (d) None of the above www.mediit.in 227 CHAPTER 09 > Strategies for Enhancement in Food Production 63 Saccharum officinarum variety of sugarcane had 52 During selection and testing of superior recombinants, selected superior plants are self-pollinated for several generation. Why? (a) (b) (c) (d) So that they reach a state of uniformity (homozygosity) So that the characters will not segregate in the progeny Both (a) and (b) Selected superior plants are not self-pollinated but cross-pollinated 53 After India independence, one of the main challenges facing the country was (a) (b) (c) (d) improving science and technology producing enough food for increasing population production of disease resistance varieties of crops Both (b) and (c) 54 Semidwarf variety of wheat was developed by (a) Norman E Borlaug (c) WY Cheung (b) MS Swaminathan (d) Fontana 55 Semidwarf variety of wheat was developed at (a) International Centre for Wheat and Maize Improvement Brazil (b) International Centre for Wheat and Maize Improvement Mexico (c) International Centre for Wheat and Rice Improvement Japan (d) International Centre for Wheat and Gram Improvement Mexico 56 Example of high yielding and disease resistant wheat variety is (c) Ratna (d) Jaya 57 Semidwarf varieties of rice were derived from IR-8 and Taichung Native-I Atlas 66 Kalyan Sona Jaya and Ratna situated at (a) New York (USA) (b) Tokyo (Japan) (c) Manilla (Philippines) (d) Hyderabad (India) 59 Where Taichung Native-1 was developed? (b) Tokyo (c) Tallinn (d) Taiwan 60 Jaya and Ratna are varieties of (a) maize 64 The genetic ability of a plant to prevent pathogens from causing disease is called (a) resistance (c) pathology (b) wheat (c) rice (d) millet 61 Saccharum barberi and Saccharum officinarum are varieties of (a) sugarcane (b) maize (c) wheat (d) rice 62 The sugarcane growing in North India and having a 65 Which one of the following is a bacterial disease? (a) (b) (c) (d) Tobacco mosaic Turnip mosaic Black rot of crucifer Late blight of potato 66 Hairy root disease of dicot plants is caused by AIIMS 2019 (a) Agrobacterium tumefaciens (b) Agrobacterium rhizogene (c) Bacillus thuringiensis (d) Meloidogyne incognita 67 Method(s) of breeding plants for acquiring disease resistance is/are (a) conventional breeding techniques (b) mutation breeding (c) tissue culture (d) Both (a) and (b) 68 The conventional method of breeding for disease (a) (b) (c) (d) screening of germplasm for resistant sources. hybridisation of selected parents. induction of mutation. Both (a) and (b) disease resistance against rust pathogens is a variety of (a) chilli (c) sugarcane Saccharum officinarum Saccharum barberi Both (a) and (b) None of the above (b) maize (d) wheat 70 Some crop varieties bred by hybridisation and selection for disease resistance to fungi, bacteria and viral disease are shown below. Fill up the blanks A to D. Crop Variety Resistance to diseases A Himgiri Leaf and stripe rust, hill bunt Brassica Pusa Swarnim (Karan rai) B Cauliflower Pusa Shubhra, Pusa Snowball K-1 Black rot and curl blight black rot Cowpea C Bacterial blight Chilli D Chilli mosaic virus, tobacco mosaic virus and leaf curl poor sugar content and yield is (a) (b) (c) (d) (b) prevention (d) None of these 69 Himgiri developed by hybridisation and selection for 58 International Rice Research Institute (IRRI) is (a) Taraiva thin stems and higher sugar content thick stems and higher sugar content thick stems and poor sugar content thin stems and poor sugar content resistance includes (a) Sonalika (b) IR-8 (a) (b) (c) (d) (a) (b) (c) (d) www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 228 (a) A–Wheat, B–White rust, C–Pusa Komal, D–Pusa Sadabahar (b) A–Pusa Sadabahar, B–Black rust, C–Pusa Komal, D–Wheat (c) A–Rice, B–White rust, C–Pusa Karan, D–Wheat (d) A–Maize, B–Brown rust, C–Pusa Karan, D–Millet 71 Triticale is the first man-made cereal crop. Mention the type of hybridisation through which it AIIMS 2018 was produced (a) (b) (c) (d) intervarietal hybridisation interspecific hybridisation intergeneric hybridisation intravarietal hybridisation Spray with bordeaux mixture Use of disease-free seeds only Use of varieties resistant to the disease All of the above 73 The process by which genetic variations are created through changes in the base sequences within genes is (b) interspecific hybridisation (d) mutation 74 The process of breeding by artificially inducing mutations with chemicals or radiations is called (a) artificial breeding (c) synthetic breeding (b) chemical breeding (d) mutation breeding 75 In mutation breeding, mutations are induced by using radiation like (a) Gamma rays (c) UV-rays (b) X-rays (d) All of these 76 In mung bean, resistance to yellow mosaic virus and powdery mildew were brought about by NEET (Odisha) 2019 (a) (b) (c) (d) mutation breeding biofortification tissue culture hybridisation and selection 77 Resistance to yellow mosaic virus in bhindi was transferred from a wild species and resulted in new variety of A. esculentus called (a) Golden Kranti (c) IR-8 (b) Sonalika (d) Parbhani Kranti 78 The host crop plants may be resistant to insect pests due to the (a) morphological characteristics (b) biochemical characteristics (c) physiological characteristics (d) All of the above (a) insect pests (c) virus (b) bacteria (d) bollworm 80 Solid stem in wheat exhibits non-preference by (a) (b) (c) (d) jassids fruit borer stem borer stem sawfly (a) sawfly (c) beetle to successfully grow chickpea in an area where bacterial blight is common. AIIMS 2018 (a) plant breeding (c) outcrossing resistance to …… . 81 In cotton, smooth leaf and the absence of nectar repel 72 Consider the following measures that could be taken (a) (b) (c) (d) 79 Hairy leaves of many plants are associated with (b) bollworms (d) jassids 82 In maize, the presence of high aspartic acid, low nitrogen and sugar content protect them from (a) (b) (c) (d) aphids fruit borers jassids stem borers 83 Some released crop varieties bred by hybridisation and selection, for insect pest resistance are given in the table. Fill up the blanks. Crops Varieties Brassica Insect pests Aphids A B Pusa Sem 2, Pusa Sem-3 Jassids, aphids and fruit borer C Pusa Sawani, Pusa A-4 Shoot and fruit borer (a) (b) (c) (d) A–Pusa Karan, B–Flat bean, C–Bhindi A–Pusa Gaurav, B–Flat bean, C–Okra A–Pusa Shubhra, B–Wrinkled bean, C–Pea A–Pusa Komal, B–Smooth bean, C–Bhindi 84 Which of the following are not disease resistant varieties? (a) Pusa Gaurav (c) Pusa Sawani (b) Pusa Sem-2 (d) All of these 85 Hidden hunger is best indicated as (a) inability of majority of people to buy enough fruits, vegetables, legumes, fish and meat and thus suffer from deficiency of vitamin, protein, etc. (b) people are unable to buy healthy drink item and thus suffer from deficiency (c) people are unable to buy junk food thus suffer from deficiency (d) All of the above 86 Majority of people suffer from malnutrition because their food does not contain essential micronutrients specially (a) iron (c) vitamin-A (b) iodine and zinc (d) All of these www.mediit.in 229 CHAPTER 09 > Strategies for Enhancement in Food Production 87 The deficiency of essential micronutrients in food may I. increase risk for disease. II. reduce mental ability. III. reduce lifespan. Choose the correct option. (a) I, II and III (c) Only I (a) I, II and IV (c) II, III and IV human nutrition is (a) (b) (c) (d) (b) I and III (d) I and II animal and human nutrition formed from certain beneficial microorganisms like for improved nutritional quality? Improve protein and oil content and quality Improve content of micronutrients and minerals Improved vitamin content All of the above 90 A biofortified wheat variety is (a) Altas 66 (c) Kalyan Sona single cell protein proteomix double cell protein All of these 93 Single cell protein is an alternative protein source for crops with increased yield crops with disease resistance herbicide resistant crops crops with high nutritive value 89 What objectives are undertaken during crop-breeding (a) (b) (c) (d) (b) All of these (d) None of these 92 One of the alternate sources of protein for animal and 88 Biofortified crops are (a) (b) (c) (d) Choose the correct option. (b) IR-8 (d) Sonalika (a) (b) (c) (d) Spirulina Methylophilus methylotrophus Both (a) and (b) None of the above 94 Microbes like Spirulina, can also be grown on industrial scale as source of good (a) fat (c) minerals (b) carbohydrate (d) All of these 95 Single cell protein reduces 91 The Indian Agricultural Research Institute, New Delhi has released several fortified vegetable crops that are rich in vitamins and minerals. They are I. Vitamin-A enriched carrot, spinach, pumpkin. II. Vitamin-C enriched bitter gourd, bathua, mustard and tomato. III. Iron and calcium enriched spinach and bathua. IV. Protein enriched broad beans, French bean, garden pea. (a) (b) (c) (d) environmental pollution greenhouse effect global warming production and growth of crop 96 250 g of Methylophilus methylotrophus bacterium has been used to produce (a) (b) (c) (d) 15 tonnes of proteins 25 tonnes of proteins 35 tonnes of proteins 50 tonnes of proteins TOPIC 4~ Tissue Culture 97 The technique of regeneration of whole plant from any part of a plant by allowing it to grow on a suitable culture under aseptic sterile conditions in vitro is called (a) (b) (c) (d) tissue culture plant culture micropropagation somatic hybridisation (a) Hormones like auxin, cytokinin, agar-agar AIIMS 2019 (b) Inorganic salt, vitamin, amino acid only (c) Carbon source like sucrose only (d) All of the above 101 To meet the demands of the society, in vitro 98 Which one is used in tissue culture? (a) Explant (c) Hybridisation 100 What are the requirements in tissue culture? JIPMER 2018 (b) Somaclones (d) None of these 99 The capacity of a cell explant to grow into a whole production of a large number of plantlets in a short duration is practiced in floriculture and horticulture industry today. It is called (a) somatic hybridisation (b) micropropagation (c) hybridoma technology (d) somaclonal variation 102 A technique of micropropagation is plant is called (a) callus (c) cellular totipotency CBSE-AIPMT 2015 (b) tissue culture (d) All of these (a) somatic hybridisation (c) protoplast fusion (b) somatic embryogenesis (d) embryo rescue www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 230 103 The plants produced from tissue culture are 108 Somatic hybrids are produced by the fusion of …… . genetically identical to the original plant from which they are grown so they are called (a) somaclones (c) para clones (b) clones (d) None of these 104 Virus free plants can be formed by (a) meristem culture (c) somatic cell culture (a) (b) (c) (d) AIIMS 2019 109 The embryo which develops from somatic cell is called (b) callus culture (d) protoplast fusion (a) (b) (c) (d) 105 Meristem culture is practiced in (a) floriculture (c) horticulture (b) aquaculture (d) pisciculture protoplasts of two cells cytoplasm of two cells nucleus of two cells DNA of two cells somatic embryo reproductive embryo sterile embryo None of the above 110 The process of fusion of protoplast of somatic cells one by tissue culture technique, which part/parts of the diseased plant will be taken? CBSE-AIPMT 2014 obtained from different varieties or species of plant on a suitable nutrient medium in vitro to develop a somatic hybrid is called (a) Apical meristem only (b) Palisade parenchyma (c) Both apical and axillary meristems (d) Epidermis only (a) (b) (c) (d) 106 To obtain virus-free healthy plants from a diseased 107 A protoplast is a cell CBSE-AIPMT 2015 somatic hybridisation cross hybridisation intravarietal hybridisation interspecific hybridisation 111 Pomato is a somatic hybrid of (a) potato and onion (c) potato and brinjal (a) without plasma membrane (b) without nucleus (c) undergoing division (d) without cell wall (b) potato and tomato (d) brinjal and tomato NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason 114 Assertion (A) Interspecific crosses are rare in nature ■ Direction (Q. Nos. 112-121) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) It both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 115 116 112 Assertion (A) Bird flu disease is the disease of poultry. Reason (R) It is caused by a bacterium. 113 Assertion (A) In tissue culture, whole plant can be produced from any plant cell. Reason (R) Plant cells possess totipotency which allow any viable plant cell to differentiate into somatic embryo that can give rise to different cells of plants. 117 118 and intergeneric crosses almost unknown. Reason (R) Interspecific cross combine undesirable features of both the parents. Assertion (A) Protoplast culture is an important technique of somatic hybrids. Reason (R) Protoplast culture technique results in the production of somatic hybrids. Assertion (A) Virus-free plants can be produced by meristem tissue culture. Reason (R) In virus infected plant, only apical mesistem is free of virus. Assertion (A) Inbreeding produces pureline. Reason (R) It causes homozygosity. Assertion (A) Hybrid vigour (heterosis) is the phenotypic superiority of hybrid over both of its parents. Reason (R) Characters of both the parents get expressed in the hybrid progeny. www.mediit.in 231 CHAPTER 09 > Strategies for Enhancement in Food Production 119 Assertion (A) Biofortification is the most practical approach to improve the health of the people suffering form hidden hunger. Reason (R) Biofortification is used to increase nutrient value of crops. 120 Assertion (A) Aquaculture practice is economically very beneficial. Reason (R) It involves breeding, rearing, harvesting and management of useful aquatic plants and animals. 121 Assertion (A) Light is an essential component of poultry farm management. Reason (R) Exposure to 14-16 hours of light ensures optimum production of eggs. II. Statement Based Questions 122 Select the incorrect statement. NEET 2019 (a) Inbreeding is essential to evolve purelines in any animals (b) Inbreeding selects harmful recessive genes that reduce fertility and productivity (c) Inbreeding helps in accumulation of superior genes and elimination of undesirable genes (d) Inbreeding increases homozygosity 123 Select the incorrect statement regarding inbreeding. NEET (Odisha) 2019 (a) Inbreeding helps in the elimination of deleterious alleles from the population (b) Inbreeding is necessary to evolve a pureline in any animals (c) Continued inbreeding reduces fertility and leads to inbreeding depression (d) Inbreeding depression cannot be overcome by outcrossing 124 Mark the incorrect statement for inbreeding. AIIMS 2019 (a) (b) (c) (d) Inbreeding depression increases productivity Inbreeding depression can be overcome by outcrossing Produces purelines Increases homozygosity 125 Which of the following statements is correct for cross-breeding? (b) In case of artificial insemination, the semen can be used immediately or can be frozen for later use (c) Controlled breeding experiments are carried out using artificial insemination and multiple ovulation embryo transfer technology (d) All of the above 127 Which of the following statements are not the main objective of animal breeding? (a) (b) (c) (d) Improved growth rate Increased production of milk, meat, egg, wool, etc. Superior quality of milk, meat, eggs, wool, etc. Improved resistance to various diseases 128 Go through the given statements and choose the correct statement. (a) (b) (c) (d) Hilsa, sardines, mackerel are freshwater fishes Catla and common carp are marine fishes Blue revolution is concerned with fisheries Both the term aquaculture and pisciculture are used for rearing fishes only 129 Which of the following statements are correct? (a) Hybrid breeding have led to the development of several high yielding varieties resistant to water stress (b) A group of animals related by descent and similar in most characters are called a breed (c) The agriculture practice of breeding and raising livestock is called animal husbandry (d) All of the above 130 Read the following statements. Choose the option for correct statement. (a) (b) (c) (d) Pusa Gaurav is a maize variety resistant to aphids Pusa A-4 is okra variety resistant to aphids Himgiri is a wheat variety resistant to hill bunt Parbhani Kranti is resistant to rust disease 131 Which statements are correct about Atlas-66? (a) It has high protein content (b) It has been used as a donor for improving cultivated wheat (c) Both (a) and (b) (d) Protina, Shakti and Rattan are three improved and biofortified hybrids of Atlas-66 132 The parameters carried out for managing dairy farm correct? are I. selection of both the male and female animals having high yielding potential and resistance to diseases. II. regular visits by a veterinary doctor. III. each animal should be fed with a balance diet. IV. pay attention to good animal management and general supervision. Which of the above statements are correct? (a) The progeny of cross-breeding may be used for commercial production (a) I and II (c) II, III and IV (a) Refers to the cross of superior male of one breed with superior female of another breed (b) Is used to produce purelines (c) Causes reduction in fertility (d) Is best for amimals below average in milk productivity, growth rate, etc. 126 Which of the following statements given below are (b) I, II and III (d) All of these www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 232 133 Animal husbandry deals with I. breeding of livestock buffaloes, cows, sheep, camels, etc. that are useful to humans. II. rearing, catching, selling, etc. of fish, molluscs and crustaceans. III. breeding plants for human use. 137 Read the given statements. I. Beehives are mostly kept close to crop fields of sunflower. II. Bee-keeping is a labour-intensive method. III. Beeswax is used in cosmetic industry. IV. Apis indica is the most common bee species. Which of the statements given above are correct? Choose the incorrect statement. (a) I and II (c) II and III (a) II and III (c) Only IV (b) I and III (d) All of these 134 Consider the following statements (I-IV) and select (b) Only II (d) None of these 138 Read the given statements. Which of them are correct the option which includes all the correct ones only. I. Single cell Spirulina can produce large quantities of food rich in protein, minerals, vitamins, etc. II. Body weight-wise the microorganism Methylophilus methylotrophus may be able to produce several times more proteins than the cows per day. III. Common button mushrooms are a very rich source of vitamin-C. IV. A rice variety has been developed which is very rich in calcium. CBSE-AIPMT 2012 about testing, release and commercialisation of new cutlivars. I. The newly selected lines are evaluated for their yield, quality and disease resistance. II. The evalution is done by recording their performance under ideal fertiliser, irrigation, etc. III. After evaluation, crops should be grown in farmer’s fields for at least three growing seasons. IV. The crop is evaluated in comparison to the best available local crop cultivar. (a) III and IV (c) II, III and IV (a) I and II (c) Only I (b) I, III and IV (d) I and II 135 Strategic steps for inbreeding are I. identify superior male and superior female of the same breed. II. identified animals are then mated in pairs. III. evaluate the progeny obtained from the mating to identify superior males and females. IV. in cattle, superior female is the cow or buffalo that produce more milk per lactation and superior male is the bull that gives rise to superior progenies. V. superior progenies obtained are further mated. Arrange the above given steps in correct sequence and select the correct answer. (a) (b) (c) (d) I → III → II →IV → V I → II → III → IV → V III → I → II → IV → V III → II → I → V → IV 136 Read the given statements about outcrossing. I. It is the breeding between animals within the same breed which do not have common ancestors on either side of their pedigree up to 4-6 generations. II. It is done to increase milk production and growth rate in animals. Which of the statement (s) given above is/are correct? (a) Only I (c) I and II (b) Only II (d) None of these (b) I, II and III (d) All of these 139 When the breeders want to incorporate desired characters into the crop plants. They should I. increase and improve yield. II. increase tolerance to salinity. III. resistance to pathogen viruses, fungi and bacteria. IV. increased tolerance to insect pests. Choose the correct option. (a) I and II (c) II, III and IV (b) I, II and III (d) All of these 140 Given below are four statements (I-IV). Which two of the following statements are correct? I. It is estimated that more than 70% of the world livestock population is in India and China. II. Maintaining cleanliness and hygiene (both of the cattle and the handlers) is important while milking, storage and transport of the milk and its products. III. Outbreeding is the breeding between animal of the same breed only. IV. Crosses between different breeds are called inbreeding. Choose the correct option (a) (b) (c) (d) I and II III and IV I and IV II and III www.mediit.in 233 CHAPTER 09 > Strategies for Enhancement in Food Production 141 Mutation breeding is carried out by I. inducing mutations in plants by high energy rays. II. screening the plant for resistance. III. selecting the desirable plant for multiplication and breeding. Choose the correct option. (a) I and II (c) II and III (b) I and III (d) All of these 142 Read the given statements. I. High aspartic acid, low nitrogen and sugar content in maize leads to resistance to maize stem borers. II. Pusa Sadabahar is a food variety resistant to chilli mosaic virus. III. Norman E Borlaug developed a semidwarf variety of wheat. IV. Germplasm collection is the collection of all sexual genes of an individual. III. Matching Type Questions 145 Match the following columns. Column I (Category of animals) Column II (Examples) A. Meat animals 1. Beef, sheep and cattle B. Poultry animals 2. Cows and buffaloes C. Milk animals 3. Chickens, turkeys and ducks D. Domesticated animal 4. Horse and camels Codes A (a) 1 (c) 2 B 3 4 C 2 1 D 4 3 A (b) 3 (d) 4 B 2 1 C 4 3 D 1 2 146 Match the following columns. Column I (Breeding types) Column II (Features) Choose the incorrect statements. A. Outcrossing (a) I and IV (c) Only IV 1. Exposes harmful recessive genes that are usually eliminated by selection B. Cross-breeding 2. Mating of animals belonging to different breeds C. Interspecific hybridisation 3 Mating of animals of same breed but having no common ancestors on either side of their pedigree for 4-6 generations D. Inbreeding 4 Mating of animals of different species (b) II and III (d) II, III and IV 143 Which of the following statement (s) is/are correct? I. The shift from grains to meat diets creates more demand for cereals. II. SCP provides a protein rich supplement. III. SCP can be produced by using bacteria, blue- green algae and fungi. IV. SCP helps to minimise environmental pollution. V. 3-10 kg of grains are required to produce 1 kg of meat by animal farming. Codes A (a) 1 (c) 3 I, II and III Only III Only IV All of the above 144 Consider the following statements. Which of them are the advantages of tissue culture/ micropropagation? I. A large number of plants can be grown in short time. II. Disease free plants can be recovered from diseased plants. III. Genetically variable plants can be produced. IV. Somatic hybrids such as pomato can be raised. Choose the correct option. (a) (b) (c) (d) I, II and III II, III and IV I, II and IV All of the above C 3 4 D 4 1 A (b) 4 (d) 2 B 3 4 C 2 3 D 1 1 147 Match the following columns. Choose the correct option. (a) (b) (c) (d) B 2 2 Column I (Terms) Column II (Related to) A. Blue revolution 1. Fish B. Green revolution 2. Agriculture C. White revolution 3. Milk Codes A (a) 1 (c) 3 B 2 2 C 3 1 A (b) 2 (d) 1 B 3 3 C 1 2 148 Match the following columns. Column I (Terms) Column II (Features) A. Pisciculture 1. Rearing of fishes B. Aquaculture 2. Rearing and management of economically useful aquatic plants and animals C. Apiculture 3. Concerned with maintenance of honeybees www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 234 Codes A (a) 3 (c) 2 152 Match the following columns. B 2 1 C 1 3 A (b) 2 (d) 1 B 3 2 C 1 3 Column I (Plants) 149 Match the following columns. Column I (Breeding types) Column II (Used for) A. MOET 1. It is done to increase milk production, growth rate in beef cattle B. Interspecific hybridisation 2. For herd improvement C. Cross-breeding 3. The progeny may be of considerable economic value D. Outcrossing 4. The progeny hybrid animals may be used for commercial production Codes A (a) 2 (b) 2 (c) 3 (d) 4 B 4 3 4 1 C 3 4 1 2 Column II (Infectious agents) A. Brown rust of wheat 1. Xanthomonas oryzae B. Bacterial blight 2. Phytophthora infestans C. Red rot of sugarcane 3. Puccinia graminis tritici D. Late blight of potato 4. Colletotrichum falcatum C 3 1 D 2 3 A (b) 1 (d) 3 B 4 1 C 2 4 D 3 2 151 Match the following columns. Column I (Plants) 1. Protein Bitter gourd, mustard and tomato 2. Iron and calcium C. Spinach and bathua 3. Vitamin-C D. Broad bean, lablab, French-bean and garden pea 4. Vitamin-A Codes A (a) 4 (b) 3 (c) 2 (d) 4 B 2 2 1 3 C 3 1 4 2 D 1 4 3 1 Wheat 1. Pusa Sadabahar B. Cauliflower 2. Pusa Komal C. Cow pea 3. Pusa Shubhra D. Chilli 4. Himgiri Column II (Improved variety name) A. Cotton 1. Erectiferum and Erectoids B. Rice 2. NP-836 C. Wheat 3. Reimi and Jagannath D. Barley 4. Indore-2 Codes A (a) 1 (c) 3 B 2 4 C 3 1 D 4 2 A (b) 4 (d) 2 B 3 1 C 2 4 D 1 3 154 Match the following columns. Column I (Organisations) Column II (Location) A. Indian Agricultural Research Institute (IARI) 1. Hyderabad B. International Crop Research Institute for Semi Arid Tropics (ICRISAT) 2. New Delhi C. National Environmental Engineering Research Institute (NEERI) 3. Shimla D. Central Potato Research Institute (CPRI) 4. Nagpur Column II (Name of improved variety) A. Codes A (a) 4 (b) 3 (c) 2 (d) 1 Carrot, spinach and pumpkin B. Column I (Plants) Column I (Plant diseases) B 1 4 A. 153 Match the following columns. D 1 1 2 3 150 Match the following columns. Codes A (a) 4 (c) 2 Column II (Nutrient present) Codes B 3 2 1 4 C 2 1 4 3 D 1 4 3 2 (a) (b) (c) (d) A 4 2 3 1 B 2 1 2 2 C 1 4 1 3 D 3 3 4 4 www.mediit.in 235 CHAPTER 09 > Strategies for Enhancement in Food Production NCERT Exemplar MULTIPLE CHOICE QUESTIONS 155 The chances of contacting bird flu from a properly 163 Use of certain chemicals and radiation to change the cooked (above 100° C) chicken and egg are base sequences of genes of crop plants is termed (a) very high (b) high (c) moderate (d) negligible (a) recombinant DNA technology (b) transgenic mechanism (c) mutation breeding (d) gene therapy 156 A group of animals which are related by descent and share many similarities are referred to as (a) breed (c) variety (b) race (d) species 157 Inbreeding is carried out in animal husbandry because it (a) increases vigour (b) improves the breed (c) increases heterozygosity (d) increases homozygosity (b) rice (d) tobacco 159 Which one of the following is not a fungal disease? (a) Rust of wheat (c) Black rot of crucifers enriched with certain desirable nutrients is called (a) crop protection (c) biofortification (b) breeding (d) bioremediation 165 Lysine and tryptophan are (a) proteins (b) non-essential amino acids (c) essential amino acids (d) aromatic amino acids 166 The term ‘totipotency’ refers to the capacity of a 158 Sonalika and Kalyan Sona are varieties of (a) wheat (c) millet 164 The scientific process by which crop plants are (b) Smut of bajra (d) Red rot of sugarcane 160 In virus-infected plants, the meristematic tissues in both apical and axillary buds are free of virus because (a) the dividing cells are virus resistant (b) meristems have antiviral compounds (c) the cell division of meristems is faster than the rate of viral multiplication (d) viruses cannot multiply within meristem cell(s) 161 Several South Indian states raise 2-3 crops of rice annually. The agronomic feature that makes this possible is because of (a) shorter rice plant (b) better irrigation facilities (c) early yielding rice variety (d) disease resistant rice variety 162 Which one of the following combination would a sugarcane farmer look for in the sugarcane crop? (a) Thick stem, long internodes, high sugar content and disease resistant (b) Thick stem, high sugar content and profuse flowering (c) Thick stem, short internodes, high sugar content, disease resistant (d) Thick stem, low sugar content and disease resistant (a) cell to generate whole plant (b) bud to generate whole plant (c) seed to germinate (d) cell to enlarge in size 167 An explant is (a) dead plant (b) part of the plant (c) part of the plant used in tissue culture (d) part of the plant that expresses a specific gene 168 The biggest constraint of plant breeding is (a) availability of desirable gene in the crop and its wild relatives (b) infrastructure (c) trained manpower (d) transfer of genes from unrelated sources 169 Micropropagation is (a) propagation of microbes in vitro (b) propagation of plants in vitro (c) propagation of cells in vitro (d) growing plants on smaller scale 170 Protoplast is (a) another name for protoplasm (b) an animal cell (c) a plant cell without a cell wall (d) a plant cell 171 More than 70% of livestock population is in (a) Denmark (c) China (b) India (d) India and China www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 236 177 Given below are a few statements regarding somatic 172 To isolate protoplast in plants, one needs (a) pectinase (c) Both (a) and (b) (b) cellulase (d) chitinase 173 Which one of the following is a marine fish? (a) Rohu (c) Catla (b) Hilsa (d) Common carp 174 The agriculture sector of India employs (a) 50% of the population (b) 70% of the population (c) 30% of the population (d) 60% of the population hybridisation. I. Protoplasts of different cells of the same plant are fused. II. Protoplasts from cells of different species can be fused. III. Treatment of cells with cellulase and pectinase is mandatory. IV. The hybrid protoplast contains characters of only one parental protoplast. Choose the correct option. (a) I and II 175 33% of India’s Gross Domestic Product comes (b) I and III (c) I and IV (d) II and III 178 Fungicides and antibiotics are chemicals that from (a) enhance yield and disease resistance (b) kill pathogenic fungi and bacteria, respectively (c) kill all pathogenic microbes (d) kill pathogenic bacteria and fungi, respectively (a) industry (b) agriculture (c) export (d) small-scale cottage industries 176 A collection of all the alleles of all the genes of a crop plant is called 179 Which one of the following products of apiculture is used in cosmetics and polishes? (a) germplasm collection (c) herbarium (b) protoplasm collection (d) somaclonal collection (a) Honey (c) Wax (b) Porp oil (d) Royal jelly Answers Mastering NCERT with MCQs 1 (a) 2 (d) 3 (d) 4 (c) 5 (a) 6 (a) 7 (d) 8 (d) 9 (d) 10 (d) 11 (d) 12 (c) 13 (a) 14 (a) 15 (a) 16 (d) 17 (b) 18 (a) 19 (a) 20 (d) 21 (a) 22 (b) 23 (c) 24 (a) 25 (a) 26 (b) 27 (d) 28 (b) 29 (a) 30 (a) 31 (d) 32 (a) 33 (b) 34 (c) 35 (a) 36 (d) 37 (d) 38 (a) 39 (d) 40 (d) 41 (d) 42 (b) 43 (a) 44 (d) 45 (d) 46 (b) 47 (d) 48 (a) 49 (d) 50 (a) 51 (c) 52 (c) 53 (b) 54 (a) 55 (b) 56 (a) 57 (a) 58 (c) 59 (d) 60 (c) 61 (a) 62 (b) 63 (b) 64 (a) 65 (c) 66 (b) 67 (d) 68 (d) 69 (d) 70 (a) 71 (c) 72 (d) 73 (d) 74 (d) 75 (d) 76 (a) 77 (d) 78 (d) 79 (a) 80 (d) 81 (b) 82 (d) 83 (b) 84 (d) 85 (a) 86 (d) 87 (a) 88 (d) 89 (d) 90 (a) 91 (b) 92 (a) 93 (c) 94 (d) 95 (a) 96 (b) 97 (a) 98 (a) 99 (c) 100 (d) 101 (b) 102 (b) 103 (a) 104 (a) 105 (a) 106 (c) 107 (d) 108 (a) 109 (a) 110 (a) 111 (b) NEET Special Types Questions 112 (c) 113 (a) 114 (c) 115 (d) 116 (c) 117 (a) 118 (a) 119 (a) 120 (a) 121 (a) 122 (b) 123 (d) 124 (a) 125 (a) 126 (d) 127 (d) 128 (c) 129 (d) 130 (c) 131 (c) 132 (d) 133 (a) 134 (d) 135 (b) 136 (c) 137 (b) 138 (d) 139 (d) 140 (a) 141 (d) 142 (c) 143 (d) 144 (c) 145 (a) 146 (c) 147 (a) 148 (d) 149 (b) 150 (d) 151 (a) 152 (d) 153 (b) 154 (b) NCERT Exemplar Questions 155 (d) 156 (a) 157 (d) 158 (a) 159 (c) 160 (c) 161 (c) 162 (a) 163 (c) 164 (c) 165 (c) 166 (a) 167 (c) 168 (a) 169 (b) 170 (c) 171 (d) 172 (c) 173 (b) 174 (d) 175 (b) 176 (a) 177 (d) 178 (b) 179 (c) www.mediit.in CHAPTER 09 > Strategies for Enhancement in Food Production 237 Answers & Explanations 9 (d) High yielding potential under the climatic conditions 14 15 17 18 21 23 24 29 30 31 37 38 42 43 l l l l l l l 26 28 process semen from chosen male is injected into reproductive tract of chosen females. By this desirable matings are performed. (a) MOET stands for Multiple Ovulation Embryo Transfer technology. It is the programme for herd improvement in animals like cattles, sheeps, rabbits, buffaloes, mares, etc. (a) In MOET, the selected cow is administered with a hormone having follicle stimulating hormone like activity to induce follicular maturation and superovulation. Due to this instead of one egg, which they normally yield per cycle, they produce 6-8 eggs. (d) During MOET fertilised eggs at 8-32 cells stages, are recovered non-surgically and transferred to surrogate mothers. The genetic mother is available for another round of superovulation. This technology has been demonstrated for cattle, sheep, rabbits, buffaloes, mares, etc. (d) Keeping beehives in crop fields during flowering period increases pollination efficiency and improves the total yield, which is beneficial in terms of crop yield and honey yield. (a) Fisheries is an industry devoted to the catching, processing or selling of fish, shell fish (prawns and molluscs) or other aquatic animals such as crabs, lobster, edible oyster, etc. (b) Pisciculture and aquaculture has contributed towards increased production of aquatic organisms. Aquaculture involves production of useful aquatic plants and animals such as fishes, prawns, shrimps, lobsters, crabs, molluscs (edible and pearl oysters) by proper utilisation of small and large bodies of water. The production of fishes is called pisciculture. It involves proper utilisation of fresh water, brackish water and coastal areas. Quick growing fishes are selected for this purpose. (a) The by products of fisheries are as follows Isinglass – Gelatinous substance obtained from the air bladder of perches and salmons used for clarification of wine and beer. Fishoil – It is extracted from the liver of sharks, etc., and has medicinal value. Manure or fishmeal – It is obtained from non-edible (waste) part of fishes, i.e. fins and tails. It is a good source of protein and given to poultry as food. Shagreen – It is the skin of sharks and rays having pointed scales used in polishing wood and other materials. (d) During the mid 1960s, Green revolution in India was witnessed, i.e. a rapid increase in the production of agricultural products (particularly wheat). It was possible due to the introduction of high yielding varieties, increased irrigation facilities, application of fertilisers and pesticides, multiple cropping and better agricultural management. 44 Answers & Explanations 13 of that area and resistance to diseases are two most important quality to be considered while selection of good breeds. (a) Bird flu is a viral disease affecting poultry birds. It resembles influenza and caused by a virus H5 N1 . (a) The improved breeds shown in the diagram are Jersey (A) and Leghorn (B). Jersey is an exotic cattle breed from Island of Jersey in english channel. Leghorn is a Mediterranean breed of chicken. Other options like Sangamneri, jamunapari and sirohi are breeds of goat. Marwari is a horse breed and beetal is a type of insect. (a) Anthrax is an infectious bacterial disease found in cattle, buffaloes, sheeps and goats. Other options like tick fever is a protozoan poultry disease. Necrosis is a form of premature cell death. Rinderpest is an infectious disease of cattle caused by virus. (b) The term ‘breed’ refers to a group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc. (a) Inbreeding refers to the mating of more closely related individuals within the same breed for 4-6 generations. The breeding strategy is as follows–superior males and superior females of the same breed are identified and mated in pairs. The progeny obtained from such matings are evaluated and superior males and females among them are identified for further mating. (a) When closely related animals of same breed are crossed continuously for few successive generations, it results in increase of homozygosity. Thus, homozygous purelines in cattles can be obtained by this method. (c) Outbreeding is an important strategy of animal husbandry because it is useful in overcoming inbreeding depression. It is the breeding of stocks or individual animals that are not closely related with each other. Inbreeding depression is the condition in which the fertility and the productivity of animals is reduced due to the continuous inbreeding in same species. Thus, outbreeding helps to restore the fertility and yield. (a) Outbreeding refers to the mating of unrelated animals belonging to Individuals of the same breed but having no common ancestors on either side for at least 4-6 generations (outcrossing). Individuals of the different breeds (cross-breeding). Individuals of different species (interspecific hybridisation). (b) The interspecific hybridisation is the mating or cross between male and female animals of two different related species belonging to same genus. This combines the desirable features. (b) Controlled breeding experiments are carried out using artificial insemination (and MOET). In this www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 238 45 (d) Green revolution was dependent mainly on plant 48 50 62 63 65 66 Answers & Explanations 67 68 71 breeding techniques for development of high yielding and disease resistant varieties of wheat, rice and maize. This was all done by the efforts of Prof. MS Swaminathan who is also called as the father of green revolution in India. (a) Genetic variability is the root of any breeding programme. Pre-existing genetic variability is collected from wild varieties, species and relatives of the cultivated crop species and preserved for later evaluation. (a) The main aim of germplasm evaluation in plant breeding programme is to identify the plants with desirable combination of characters. The identified plants are then propagated and used in the process of hybridisation to create improved progeny or purelines. (b) The sugarcane, Saccharum barberi was originally grown in North India, but had poor sugar content and yield. (b) Tropical cane grown in South India is Saccharum officinarum had thicker stems and higher sugar content. Both varieties of sugar cane, i.e. Saccharum barberi and Saccharum officinarum were suceessfully crossed to get sugar cane varieties combining the desirable qualities of high yield, thick stem, high sugar and ability to grow in the sugar cane areas of North India. (c) Black rot of crucifer is a bacterial disease. Tobacco mosaic and turnip mosaic are viral diseases and late blight of potato is caused by fungi. (b) Hairy root disease of dicot plants is caused by Agrobacterium rhizogene. Agrobacterium tumefaciens causes stem gall of coriander. Bacillus thuringiensis is soil dwelling Gram positive bacterium, now being using as pesticide against cotton stem borer insect. Meloidgyne incognita causes root knot disease in tomato and brinjal. (d) Plant breeding is carried out by the conventional breeding techniques or by mutation breeding. The conventional method of breeding for disease resistance is that of hybridisation and selection. Mutation breeding is defined as the process of breeding by artificially inducing mutations using chemicals (like aniline) or radiations like (gamma radiation). (d) The conventional method of breeding for disease resistance includes screening of germplasm for resistant sources and hybridisation of selected parents. Whereas, induction of mutation is done under mutation breeding technique. (c) Intergeneric crosses are made between plants belonging to different genera of the same family. The hybrids produced by this method are both scientifically as well as agronomically significant. For example, Triticale the first man made cereal crop is an allopolyploid, which was produced by intergenic hybridisation between wheat (Triticale) and rye (Secale). 72 (d) All measures can be taken to cultivate disease free 73 75 79 84 85 86 88 90 92 93 94 chickpea crop. Bacterial blight of chickpea is caused by bacterium Xanthomonas campestris. The stem and the leaves of infected plant give blighted or burnt up appearance. Control measures include roguing 3-years crop rotation, disease-free seeds, spray of copper fungicides (bordeaux mixture) and use antibiotics besides sowing disease resistant varieties. (d) Mutation is the process by which genetic variations are created through changes in the base sequence within genes. It results in the creation of a new character or trait not found in the parental type. (d) Mutations to create a new character or trait can be artificially induced through the use of chemicals (like hydrazine, methyl methane sulphonate, etc.) or radiations (like X-rays, UV-rays and γ-rays, etc). These agents are called as mutagens. (a) Hairy leaves of many plants are associated with resistance to insect pests. For example, resistance to jassids in cotton and cereal leaf beetle in wheat. (d) All options are not the disease resistant varieties. These all are insect pest resistant varieties. Pusa Gaurav is the variety of Brassica which resistant to aphids, Pusa Sem-2 is the variety of flat bean and resistant to jassids, aphids and fruit borer, while Pusa Sawani is the variety of okra which is resistant to shoot and fruit borers. (a) Hidden hunger is indicated as the lack of protein, vitamins and micronutrients deficiencies in the food. This is because not all people can afford to buy adequate vegetable, fruits, legumes, fish and meat. Thus, more than 840 million people in the world suffering from hidden hunger. (d) Majority of people suffer from hidden hunger or malnutrition because their food does not contain essential micronutrients particularly iron, iodine, zinc and vitamin-A. (d) Biofortified crops are the crops with high nutritive value. These crops have high levels of vitamins and minerals or higher proteins and healthier fats. They are developed by the process of biofortification. (a) Atlas 66 is a biofortified wheat crop having high amount of amino acid and protein content. (a) One of the alternate sources of protein for animal and human nutrition is single cell protein. It is the production of edible proteins on a large scale by cultivation of microorganisms. (c) Single cell proteins are formed from certain beneficial microorganisms like — Methylophilus methylotrophus Bacteria Cyanobacteria — Spirulina. (d) Microbes are being grown on an industrial scale as source of good protein. Blue-green algae like Spirulina can be grown easily on materials like waste water from potato processing plants (containing starch), straw, molasses, animal manure and even sewage, to produce large quantities and can serve as food rich in protein, minerals, fats carbohydrate and vitamins. www.mediit.in 95 (a) The microorganisms used in the production of SCP 96 98 99 100 102 103 104 use substrates like sewage, animal manure, etc., which cause pollution. Therefore, by utilisation of such kind of substrates in the production of SCP helps in reduction of environmental pollution. (b) 250 g of microorganism like Methylophilus methylotrophus, because of its high rate of biomass production and growth, can be expected to produce 25 tonnes of protein. (a) Explant is used in plant tissue culture. It is an excised plant part which has the potential to give rise to whole new plant, e.g. leaves, shoot, roots, nodes, etc. The plants obtained through this techniques are morphologically and genetically similar to each other and to their parents plant. (c) Cellular totipotency is the ability of a explant to give rise to a complete plant, when cultured in a suitable culture medium at appropriate temperature and aeration conditions. (d) The requirements of tissue culture are growth hormones (auxin, cytokinin), agar-agar, inorganic salts, vitamins, amino acids, carbon source like sucrose, etc. In plants tissue culture, the medium on which explants are cultured is known as nutrient or culture medium. It acts as a source of important nutrient required for proper development of explant. (b) Somatic embryogenesis is a technique of micropropagation. It is the growing of plants from meristematic tissue of somatic cells of plants on suitable nutrient media under controlled conditions. (a) Somaclones are plants produced from tissue culture which are genetically identical to the original plant from which they are grown. Somaclones are produced by micropropagation technique of tissue culture. (a) Virus free plants can be formed by meristem cutlure. The reason behind this is that virus cannot propagate in rapidly dividing cells, so meristematic zones of plant always remain virus free. For other options, Protoplast fusion technique is used for making somatic hybrids. Somatic cell culture technique is used to propagate plants from somatic cells using nutrient medium and combination of hormones. Callus culture is undifferentiated mass of tissue. Growing callus from plant organs is called callus culture. (a) In floriculture, the practice of meristem culture is used. Floriculture refers to large scale production of flowers for economic purposes. Other options like aquaculture and pisciculture are related to fisheries. (c) In virus infected plant, both apical and axillary meristems are free of virus and use for the healthy plant cultivation because of rapid cell divisions and strong interferon activity in this region. These tissues form a protective impermeable covering around themselves, which is non-penetrable by any pathogen. Hence, these l 107 108 111 112 113 114 115 116 l l 105 106 117 118 tissues are used in the production of diseased free plants by tissue culture. (d) A protoplast is a cell without cell wall . It is a cell that had its cell wall completely or partially removed using either mechanical or enzymatic means. (a) Somatic hybrids are produced by the fusion of protoplasts of two cells, each having a desirable character. (b) Pomato is a somatic hybrid obtained by a mating between potato and tomato whereas bomato is a somatic hybrid between brinjal and tomato. (c) Assertion is true, but Reason is false. Reason can be corrected as Bird flu is a disease of poultry caused by a virus H5 N1 . The virus enters the human body through contact with sick birds or their products. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. In tissue culture, somatic embryos or embryoids are non-zygotic embryo like structures that develop in vitro cultures from somatic cells of any type of tissue. Here ‘totipotency’ property of plants cells is used, which allow whole plant to be produced from any one plant cell. (c) Assertion is true, but Reason is false. Reason can be corrected as In interspecific crosses, male and female animals of the different related species are mated. The resultant progeny may combine desirable features of both the parents are infertile. Thus, are rare in nature. The same applies to intergeneric crosses. It is the crossing of two different animals/plants of different genus. It is almost unknown in nature as the gametes show species specificity. (d) Assertion is false, but Reason is true. Assertion can be corrected as Protoplast culture is an important technique of tissue culture and this technique results in the production of somatic hybrid plants. (c) Assertion is true, but Reason is false. Reason can be corrected as Virus-free plants can be produced from the virus infected plants by means of meristem tissue culture. In a diseased plant, both the apical and axillary meristems are free of virus. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Inbreeding is breeding between animals of the same breed for 4-6 generations. Continued inbreeding causes homozygosity which produces purelines. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Heterosis (Hybrid vigour) is the phenotypic superiority of the hybrid over both of its parents in one or more traits. In other words, when two unrelated individuals or lines are crossed, the performance of F1 hybrid is often superior to both its parents. 239 Answers & Explanations CHAPTER 09 > Strategies for Enhancement in Food Production www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 240 119 (a) Both Assertion and Reason are true and Reason is 120 121 122 123 Answers & Explanations 124 125 127 the correct explanation of Assertion. Biofortification is breeding of crops with higher levels of vitamins and minerals or higher protein and healthier fats. This increase nutrient value of crops. Since billions of people in the world suffer from nutrient deficiencies or hidden hunger. Biofortification of crops is the most practical approach to improve the health of these people. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Aquaculture is the breeding, rearing, harvesting and management of economically useful aquatic organisms like fishes, shellfish, molluscs, crustaceans and other aquatic plants. It is done to procure food and other commercial products, restore habitats and replenish the depleted stocks, etc. (a) Both Assertion and Reason are correct and Reason is the correct explanation of Assertion. Light is an essential component of poultry farm management because it determines the quantity of egg production. An exposure to 14-16 hours of light period during daytime ensures optimum production of eggs. (b) Statement in option (b) is incorrect. It can be corrected as Inbreeding does not select harmful recessive genes. It exposes harmful recessive genes that reduce fertility and productivity and these are eliminated by selection. Statement in other options are correct. (d) Statement in option (d) is incorrect. It can be corrected as Inbreeding depression can be overcome by outcrossing. In this method, mating of animals within the same breed, but no common ancestor for 4-6 generations. Statements in other options are correct. (a) Statement in option (a) is incorrect about inbreeding. It can be corrected as Inbreeding depression decreases the productivity. Continued inbreeding, usually reduces fertility of animals and even their productivity. This condition is called as inbreeding depression. (a) Only statement in option (a) is correct, while other are incorrect. These can be corrected as Mating of individuals from entirely different breed is called cross-breeding. It is the method of breeding superior male of one breed with superior female of another breed in order to combine the desirable qualities of two different breeds in the progeny. (d) Statements in option (a), (b) and (c) are correct, but (d) is incorrect. It can be corrected as Animal breeding involves crosses between useful animal breeds aiming to increase the yield of animals and to improve the desirable qualities of the product. It has no concern with the development of resistance against diseases. 128 (c) Only statement in option (c) is correct, while the other statements are incorrect and can be corrected as Hilsa, sardines, mackerel are marine fishes. Catla and common carp are freshwater fishes. Only the term pisciculture is used for rearing fishes only. (c) Only statement in option (c) is correct. Rest other statements are incorrect. These can be corrected as Pusa Gaurav is variety of Brassica, resistant to aphids. Pusa A-4 is okra variety resistant to shoot and fruit borer. Parbhani kranti is resistant to yellow mosaic virus. (c) Statements in option (a) and (b) are correct for Altas 66. It is a soft wheat that has been used since 1953 as a genetic source of higher protein in wheat. It has been used as a donor for cultivated wheat. Statement in option (d) is incorrect. The correct form of this statement is Protina, Shakti and Rattan are three lysine rich maize hybrids developed in India. (a) Statements I and II are correct for animal husbandry. Statement III is incorrect and can be corrected as Animal husbandry does not deal with breeding plants for human use. It is a component of plant breeding programmes. (d) Out of the given statements I and II are correct, while III and IV are incorrect. The correct form of these statements is Common button mushrooms are a very rich source of vitamin-B A rice variety has been developed, by IARI which is rich in iron. (b) Option (b) represents the correct answer. Inbreeding involves Identification of superior males and superior females of the same breed. Mating of the superior animals. Progeny obtained from such mating are evaluated and assessed for the desirable traits. It should be kept in mind that a superior cow or buffalo is that which gives more milk per lactation. Similarly, a superior bull is that which gives rise to superior progeny as compared to those of other bulls. This process of mating of superior progenies is continued for 4-6 generations. (b) Only statement II is incorrect, while the rest are correct. The incorrect statement can be corrected as Bee-keeping is not a labour-intensive method. (a) Statements I and II are correct, while III and IV are incorrect. The correct form of these statement are Outbreeding is the breeding between the animals of the same breed but no common ancestors or different breeds or different species. Crosses between the same breeds are called inbreeding. l l l 130 l l l 131 133 134 l l 135 l l l l l 137 140 l l www.mediit.in CHAPTER 09 > Strategies for Enhancement in Food Production 142 (c) Only statement IV is incorrect. The correct form of 155 156 157 158 159 161 162 163 164 166 167 168 169 170 172 173 176 177 breeding. Use of radiations is not involved in other three options. (c) Biofortification is the scientific process by which crop plants are enriched with higher levels of vitamins and minerals or higher protein and healthier fats. It is the most practical means to improve public health. (a) The capacity of a cell or an explant to grow and develop into a whole plant is called ‘totipotency’. (c) Any part of a plant used in tissue culture, which is taken out and grown in a test tube under sterile conditions in a special nutrient media is called an explant. A whole plant can be generated from an explant. (a) The biggest constraint of plant breeding (conventional) is the availability of limited number of disease resistance genes that are present and identified in various crop varieties or wild relatives. (b) Micropropagation is propagation of plants in vitro to achieve a large number of plants in very short duration. This results in the production of genetically identical plants and is widely used in forestry and floriculture. (c) A protoplast is a plant, bacterial or fungal cell whose cell wall is completely or partially removed using either mechanical or enzymatic means. (c) Both option (a) and (b) are correct. As the cell wall of plant cells consists of pectin and cellulose which can be removed by digestion with combination of enzymes pectinase and cellulase to isolate the protoplast. (b) Hilsa, sardines, mackerel and pomfrets are some of the marine fishes.Catla, rohu and common carp are freshwater fishes. (a) Germplasm collection is the entire collection of plants/seeds having all the diverse alleles for all genes in a given crop. (d) Statements II and III are correct, while I and IV are incorrect and can be corrected as Protoplasts from two different varieties of plants are fused in the somatic hybridisation. The hybrid protoplast contains characters of both parental protoplast. (c) Beeswax is the most common product of apiculture which finds many uses in industry, cosmetics and polishes of various kinds. Honey is a food of high nutritive value and also finds use in the indigenous systems of medicine. Royal jelly, is the queenbees extraordinary source of food. It is rich in nutrition values and is believed to be a potent antioxidant. Prop oil is not a product of apiculture. l l 179 Answers & Explanations 144 this statement is Germplasm collection is the entire collection of plants or seeds having all the diverse alleles for all genes in a given crop. Rest other statements are correct. (c) Statements I, II and IV represent the advantages of tissue culture/micropropagation, while statement III is incorrect and can be corrected as Genetically, similar plants can be produced by the method of tissue culture. (d) The chances of contacting bird flu from a properly cooked (above 100°C) chicken and egg are negligible. Highly pathogenic strains of avian influenza can be found inside and on the surface of eggs. In an infected bird, it may spread to all the parts including the meat. However, proper cooking at or above 70°C, prior to eating, will inactivate the virus in the egg as well as in the meat. (a) A group of animals that are related by descent and are similar in most characters like general appearance, features, size, configuration, etc., are said to belong to a breed. (d) Inbreeding increases homozygosity, i.e. state of possessing two identical alleles, one inherited from each parent. It is necessary if we want to evolve a pureline in any animal. (a) Sonalika and Kalyan Sona are outstanding semi dwarf varieties of wheat possessing good yield potential and disease resistant. These were developed in 1963. (c) Black rot of crucifers is not a fungal disease. It is caused by a bacteria, Xanthomonas campestris. Other three diseases are caused by fungal pathogens. (c) Several South Indian states raise 2-3 crops of rice annually. The agronomic feature that makes this possible is early yielding rice variety. These varieties are a group of crops created intentionally during the green revolution to increase global food production. (a) In the sugarcane crop, a sugarcane farmer looks for a combination of thick stem, long internodes, high sugar content and disease resistance. In practice, Saccharum barberi and Saccharum officinarum are being crossed to develop such a combination. (c) It is possible to induce mutations artificially in crop plants through the use of chemicals or radiations (like gamma radiations), and then selecting and using those plants that have the desirable character as a source of further breeding. This process is called mutation 241 www.mediit.in CHAPTER > 10 Microbes in Human Welfare NEET KEY NOTES Å Microbes are microscopic, single-celled, minute organisms that individually are too small to be seen with naked eyes, i.e. can be seen only under a microscope. Å Microbes constitute major groups of biological systems on the earth, which are present almost everywhere, i.e. in soil, air, water, on/in plants and animals and also even inside our body. These can be found in extreme conditions of pH (alkaline and acidic soil) and temperature (thermal vents or geysers and below the several metre thick snow layers). Å Å Microbes are diverse group of organisms including protozoans, bacteria, fungi, microscopic plants, viruses, viroids and prions (proteinaceous infectious agents), etc. Some microbes cause infections and diseases in human beings, animals and plants. But several microbes are useful to man in diverse ways. Microbes in Household Products Å Å We use microbes and microbe derived products almost everyday. Curd is made by Lactobacillus and other bacteria commonly called Lactic Acid Bacteria (LAB), which grow in milk and convert it to curd. A small amount of curd added to the fresh milk as inoculum or starter contains millions of LAB, which at suitable temperature multiply and produce acids that coagulate and partially digest the milk proteins. It also increases the content of vitamin-B12 in curd making it more nutritious and helps in replacing disease causing microbes in the stomach. Å The dough used for making foods such as dosa, idli, cakes and bread is fermented by using baker’s yeast (Saccharomyces cerevisiae). The puffed up appearance of dough is due to the production of CO 2 . Å A traditional drink of Southern India called ‘toddy’ is also made by fermenting sap from palms. Å Cheese of different textures, flavours, etc., are also made by using different microbes, e.g. the holes in ‘Swiss cheese’ are due to the production of a large amount of CO 2 by a bacterium called ‘Propionibacterium shermanii’. Å The ‘Roquefort cheese’ is ripened by growing a specific fungi (Penicillium roqueforti) on them, which gives them a particular flavour. Microbes in Industrial Products In industry, microbes are used to make a number of products such as beverages, enzymes and antibiotics, etc., valuable to human beings. Industrial scale production requires growing microbes in very large vessels called fermentors. Fermented Beverages Å Large scale production of beer, brandy, whisky, rum, etc., is done by fermenting malted cereals and fruit juices using unicellular fungi Saccharomyces cerevisiae (brewer’s yeast). Å Different types of alcoholic drink like wine and beer are produced without distillation. Whisky, brandy and rum are produced by distillation of the fermented broth. www.mediit.in 243 CHAPTER 10 > Microbes in Human Welfare disposed, in water bodies, it needs to be treated in Sewage Treatment Plants (STPs) to make it less polluting. Antibiotics Å Å These are the chemical substances which are produced by some microbes to kill or retard the growth of other disease causing microbes. Penicillin was the first antibiotic to be discovered by Alexander Fleming. Alexander Fleming had observed that if a mould of Penicillium notatum grows on a nutrient medium, it does not let a bacterium Staphylococcus grow around it. He isolated the chemical produced by the mould and named it penicillin. However, its full potential as an effective antibiotic was established later on by Ernst Chain and Howard Florey. For this discovery, Fleming, Chain and Florey were awarded the Nobel Prize in 1945. Å Antibiotics are widely used in treating human and animal bacterial diseases. Deadly diseases like plague, whooping cough (kali khansi), diphtheria, leprosy (kusht rog) are completely curable diseases now due to the use of antibiotics. Å One of the most productive sources of antibiotics has been the genus–Streptomyces from which many antibiotics have been derived. Some of them are streptomycin, tetracycline, erythromycin, terramycin, which are obtained from Streptomyces griseus, S. aureofaciens, S. erethreus and S. remosus, respectively. Chemicals, Enzymes and Other Bioactive Molecules Å Yeast (Saccharomyces cerevisiae) is used for the commercial production of ethanol. Å Microbes are also used for the production of enzymes. Lipases are used in detergent formulations to remove oily stains from laundry. Pectinases and proteases are used to clarify bottled juices. Streptokinase produced from Streptococcus (a bacterium) is used as a ‘clot buster’ for removing blood clots from blood vessels of patients. In organ transplant patients, a bioactive molecule cyclosporin-A acts as an immunosuppressant and is produced by Trichoderma polysporum (fungi) and statins act as blood cholesterol lowering agent and are obtained from the yeast, Monascus purpureus. Microbes in Sewage Treatment Å Certain heterotrophic microbes naturally present in sewage are used in its treatment. This treatment is carried out in two stages, i.e. primary treatment and secondary treatment. Å In primary treatment, physical removal of particles, i.e. large and small, is done from the sewage through filtration and sedimentation. All solids that settle down, form the primary sludge and the supernatant forms the effluent, which is taken for secondary treatment. Å In secondary treatment or biological treatment, the primary effluent is passed into large aeration tanks where it is constantly agitated mechanically. This allows the growth of the aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures) which consume the major part of the organic matter in the effluent that significantly reduces the BOD (Biochemical Oxygen Demand) of the effluent. Å BOD is the amount of oxygen that would be consumed, if all the organic matter in one litre of water were oxidised by bacteria. The sewage water is treated till the BOD is reduced. The greater is the BOD of wastewater, more is its polluting potential. Å The effluent is then passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called activated sludge as it contains active microbes. From here Many fungi and bacteria are used for commercial production of organic acids like citric acid produced by Aspergillus niger (a fungus), acetic acid produced by Acetobacter aceti (a bacterium), butyric acid produced by Clostridium butylicum (a bacterium) and lactic acid produced by Lactobacillus (a bacterium). Å Å Å Sewage is the municipal wastewater generated everyday in cities and towns. It contains large amounts of organic matter and many pathogenic microbes. That is why before being n n n A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, lack of oxygen kills the aerobic bacteria which are digested along with the other biomass by anaerobic bacteria and fungi. The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams. Å During digestion of organic matter, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas, which is inflammable and can be used as a fuel. Å The ministry of environment and forests has initiated the Ganga Action Plan and Yamuna Action Plan to save these major rivers of our country from pollution. These plans propose to build a large number of sewage treatment plants, so that only treated sewage may be discharged into the rivers. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 244 Microbes in Production of Biogas Å Biogas is a mixture of gases (mainly CH 4 , CO 2 , H 2 ) produced by certain bacteria, which grow anaerobically on cellulosic material. These bacteria are collectively called methanogens and are found in the anaerobic sludge generated during sewage treatment and in the rumen (a part of stomach) of cattle, helping in the breakdown of cellulose. It plays an important role in the nutrition of cattle. Thus, the excreta (dung) of cattle, commonly called gobar (which is rich in methanogenic bacteria) can be used for generation of biogas, commonly called as gobar gas. Å Biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and slurry of dung is fed. Methanobacterium in the dung acts on the biowaste to produce biogas (used for cooking and lighting). Å The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. Spent slurry removed from plant can be used as fertiliser. Å Biogas production technology was developed in India mainly by IARI (Indian Agricultural Research Institute) and KVIC (Khadi and Village Industries Commission). Microbes as Biocontrol Agents Å Biocontrol refers to the use of biological methods for controlling various plant diseases and pests. Å This method is employed because the long time use of chemical insecticides, pesticides and weedicides has been proved to be harmful for all living organisms and the environment (air, water, soil, etc). Å Biological control of pests and diseases The use of biocontrol measures has become more preferable since it greatly reduces our dependence on toxic chemicals. Here, pests can be controlled by making use of natural predation rather than chemicals. by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. This will kill the caterpillars, but leave other insects unharmed. n n Å Biocontrol involves creation of a system where the insects/pests are not eradicated rather are kept at manageable levels by a system of check and balances within ecosystem. Various microbes can be used as biocontrol agents, e.g. Aphids and mosquitoes can be controlled by ladybird beetle and dragonflies, respectively. Butterfly caterpillars can be killed by using the bacteria Bacillus thuringiensis. Bt is available as dried spores which are mixed with water and sprayed on to plants such as brassicas and fruit trees, where these are eaten n n NEET Viruses (like baculoviruses belonging to genus Nucleopolyhedrovirus) are excellent for species specific, narrow spectrum insectivides. These do not have negative impact on non-target insects and have narrow spectrum insecticidal applications. Integrated Pest Management (IPM) is an environmentally sensitive and effective approach of pest management that uses information on life cycles of organisms and their interaction with environment. The integrated pest management is done to control insects and pests of plants, animals and humans. Microbes as Biofertilisers Å To cut down the pollution caused by chemical fertilisers, it is important to switch to organic farming (raising crops through the use of components of biological origin, e.g. biofertilisers). Å Biofertilisers are organisms, e.g. bacteria, fungi and cyanobacteria that enrich the nutrient quality of the soil. Å The main sources of biofertilisers are as follows n Å Fungi (like Trichoderma sp., a free-living fungi, that are common in root ecosystems) are effective against several fungal plant pathogens. n n n n n Bacteria Rhizobium is a symbiotic bacterium living in the root nodules of legumes and fixes atmospheric nitrogen into organic compounds. Azotobacter and Azospirillum are free-living bacteria, which fix atmospheric nitrogen from the air and thus, enrich the nitrogen content of the soil. Fungi form symbiotic association with plants (mycorrhiza), which absorb phosphorus from the soil and pass it on to the plants. Many members of genus Glomus form mycorrhiza. Plants with mycorrhizal association show other benefits also, such as Resistance to root borne pathogens. Tolerance to salinity and drought. Increase in plant growth and development. Cyanobacteria are autotrophic microbes found in aquatic and terrestrial environments. Many of them fix-nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as important biofertiliser, it also adds organic matter to the soil, thus increasing its fertility. KEY NOTES www.mediit.in CHAPTER 10 > Microbes in Human Welfare 245 Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Basic Concepts and Microbes in Household Products 1 Microorganisms or microbes are found in (a) (b) (c) (d) soil, air, water and inside the bodies of living organisms thermal vents deep in soil under snow and in highly acidic environments All of the above 2 The microscopic proteinaceous infectious agents are (a) viroids (c) protozoans called (a) (b) (c) (d) Citric Acid Bacteria (CAB) Lactic Acid Bacteria (LAB) Tartaric Acid Bacteria (TAB) Formic Acid Bacteria (FAB) 7 The most abundant prokaryotes helpful to human in (b) prions (d) bacteria 3 The nutritive medium for growing bacteria and many fungi in the laboratory is called (a) (b) (c) (d) 6 Microorganisms such as Lactobacillus are commonly culture media fermentation media baking media None of the above making curd from milk and in the production of antibiotics are the ones categorised as (a) cyanobacteria (b) archaebacteria (c) chemosynthetic autotrophs (d) heterotrophic bacteria 8 The starter or inoculum is added to the fresh milk in 4 Given below is the diagram of a bacteriophage. In which one of the option, all the six parts A, B, C, D, E and F are correct? A order to convert milk into curd and improves its nutritional quality by increasing (a) vitamin-B12 (c) calcium formation from milk and select the correct option for A and B. Curd is added as inoculum to the fresh milk C LAB shows growth in milk D Production of ..... A ..... starts Coagulation and digestion of milk protein E (a) A–Head, B–Tail, C–Collar, D–Pins, E–Plate, F–Prongs (b) A–Head, B–Collar, C–Tail, D–Plate, E–Pins, F–Prongs (c) A–Head, B–Tail, C–Collar, D–Plate, E–Prongs, F–Pins (d) A–Head, B–Collar, C–Tail, D–Pins, E–Plate, F–Prongs 5 Which of the following bacteria convert milk into curd? (a) (b) (c) (d) (b) protein (d) All of these 9 Study the following flowchart that shows curd B F CBSE-AIPMT 2012 Propionibacterium shermanii Saccharomyces cerevisiae Lactobacillus Thermophilic bacteria Improved nutritional quality by increased ..... B ..... (a) (b) (c) (d) A–citric acid, B–vitamin-B12 A–lactic acid, B–vitamin-B12 A–lactic acid, B–vitamin-C A–citric acid, B–vitamin-B 2 10 Which gas is released during the process of fermentation that gives the puffy appearance to dough for making bread? (a) CO2 (c) O2 (b) CO (d) H2 www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 246 11 Toddy, a traditional drink of Southern India is made by 13 Roquefort cheese is formed by ripening with ...A...for ...A... of sap from …B… tree. Here, A and B refer to a particular flavour. Here A refers to (a) A–fermentation, B–palm (b) A–fermentation, B–bamboo (c) A–distillation, B–palm (d) A–distillation, B–bamboo (a) yeast (c) bacteria 14 Which of the following food items are produced through fermentation by the microorganisms? I. Idli II. Dosa IV. Cheese III. Toddy Choose the correct option. 12 Swiss cheese is formed by the bacterium (a) (b) (c) (d) (b) fungi (d) None of these Aspergillus niger Lactobacillus Propionibacterium shemanii Penicillium roqueforti (a) I, II and III (c) II, III and IV (b) I, III and IV (d) All of these TOPIC 2 ~ Microbes in Industrial Products 15 Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes? NEET 2019 (a) Sludge digester (c) Bioreactor (b) Industrial oven (d) BOD incubator 16 The alcoholic beverages produced by the distillation of the fermented broth are (a) (b) (c) (d) wine and beer wine, whisky and brandy whisky, brandy and rum whisky, beer and brandy used to treat American soldiers wounded in World War-II? (a) Streptokinase (c) Statins production of beverages like wine, beer, whisky brandy or rum? 22 Who got Nobel Prize in 1945 for the discovery of penicillin as an antibiotic? (a) Alexander Fleming (c) Howard Florey Clostridium butylicum Aspergillus niger Saccharomyces cerevisiae Penicillium notatum (a) (b) (c) (d) diphtheria, whooping cough plague leprosy All of the above following table and select the correct answer. Types of microbes Scientific names Bacterium CBSE-AIPMT 2012 (a) citric acid and lactic acid (b) lipase and pectinase (c) bread and beer (d) cheese and butter 19 Brewer’s yeast is Penicillium notatum Trichoderma polysporum Propionibacterium shermanii Saccharomyces cerevisiae 20 Who observed a mould growing in unwashed culture plate while working on Staphylococcus bacterium? (a) Ernst Chain (c) Lamarck (b) Ernst Chain (d) All of these 24 Identify the blank spaces A, B, C and D given in the 18 Yeast is used in the production of (a) (b) (c) (d) (b) Penicillin (d) Neomycin 23 Antibiotics are used to treat diseases like 17 Which of the following organisms is used in the (a) (b) (c) (d) 21 Which one of the following antibiotics was extensively (b) Alexander Fleming (d) Florey A Commercial products Lactic acid Fungus B Citric acid C Acetobacter aceti Acetic acid Fungus Penicillium notatum D (a) A–Lactobacillus, B–Aspergillus niger, C–Bacterium, D–Penicillin (b) A–Staphylococcus, B–Clostridium, C–Yeast, D–Penicillin (c) A–Lactobacillus, B–Microsporum, C–Yeast, D–Penicillin (d) A–Staphylococcus, B–Microsporum, C–Agaricus, D–Penicillin 25 Which one of these microbes is used in the commercial production of butyric acid? (a) (b) (c) (d) Clostridium butylicum Streptococcus butylicum Trichoderma polysporum Saccharomyces cerevisiae www.mediit.in CHAPTER 10 > Microbes in Human Welfare 26 Which of the following is correctly matched for the product produced by them? (a) (b) (c) (d) NEET 2019 Acetobacter aceti – Antibiotics Methanobacterium – Lactic acid Penicillium notatum – Acetic acid Saccharomyces cerevisiae – Ethanol 27 Choose the incorrect pair. 247 30 Monascus purpureus is a yeast used commercially in the production of 31 Which of the following is a commercial blood (a) Lipases – Used in detergents for removing oil stains (b) Pectinases and proteases – Used in clarifying bottled juices (c) Statins – Competitively inhibit the enzyme responsible for cholesterol synthesis (d) None of the above 28 Which of the following is used as ‘clot buster’ for cholesterol lowering agent? (a) (b) (c) (d) (b) Statins (d) Streptokinase 29 Identify the blank spaces A, B, C and D given in the following table and select the correct answer. Types of microbes Fungus C Scientific names A Monascus purpureus Medical Products applications Cyclosporin-A B Statin D (a) A–Trichoderma polysporum, B–As an immunosuppressive agent in organ transplant patients, C–Yeast, D–As blood-cholesterol lowering agent (b) A–Trichoderma polysporum, B–As blood-cholesterol lowering agent, C–Protozoa, D–As an immunosuppressive agent in organ transplant patients (c) A–Clostridium butylicum, B–Used as a clot-buster, C–Yeast, D–As blood- cholesterol lowering agent (d) A–Clostridium butylicum, B–As blood-cholesterol lowering agent, C–Yeast, D–Used as a clot-buster NEET 2019 Statin Streptokinase Lipases Cyclosporin-A 32 Which of the following is incorrectly matched in the given table? removing clots from blood vessels of patient who have undergone myocardial infarction? (a) Ethanol (c) Cyclosporin-A CBSE-AIPMT 2012 (a) ethanol (b) streptokinase for removing clots from the blood vessels (c) citric acid (d) blood cholesterol lowering agent, statins Microbes (a) Monascus purpureus (b) Streptococcus (c) Clostridium butylicum (d) Trichoderma polysporum NEET 2016 Products Statins Applications Lowering of blood cholesterol Streptokinase Removal of clot from blood vessel Lipase Removal of oil stains Cyclosporin-A Immunosppressive drug 33 Which industrial products are synthesised from microbes? I. Antibiotics II. Toddy III. Bioactive molecules IV. Bread Choose the correct option. (a) (b) (c) (d) I, II, III and IV II, III and IV I and IV III and IV TOPIC 3 ~ Microbes in Sewage Treatment 34 Sewage contains large amounts of …A… and …B… . Here A and B refer to (a) (b) (c) (d) A–inorganic matter, B–bacteria A–organic matter, B–pathogenic microbes A–organic matter, B–virus A–inorganic matter, B–pathogenic microbes 35 Primary treatment of wastes is the (a) physical removal of large and small particles from sewage (b) biological removal of large and small particles from sewage (c) Both (a) and (b) (d) chemical removal of large and small particles from sewage 36 In the primary treatment of sewage, the floating debris is removed by sequential ... by passing through wire mesh screens. The most appropriate word for filling the blank is (a) filtration (c) condensation (b) sedimentation (d) evaporation 37 In the primary treatment of sewage, the soil and small pebbles are removed by (a) filtration (b) sedimentation (c) condensation (d) evaporation www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 248 38 Which one of the following in sewage treatment removes suspended solids? (a) Tertiary treatment (c) Primary treatment NEET 2017 (b) Secondary treatment (d) Sludge treatment 39 In the biological treatment of sewage, the masses of bacteria held together by fungal filament to form mesh-like structures called as (a) activated sludge (c) flocs (b) aerobic process (d) anaerobic sludge 40 Choose the correct option to fill in the blanks. I. Primary treatment of sewage involves physical removal of small and large particles through ...A... and ...B... . II. Microbes consume the major part of organic matter in the effluent and reduce ...C... of sewage. III. ...D... particularly ...E... anaerobically breakdown cellulosic material and produce CO2 and H2 from anaerobic sludge during ...F... . treatment. IV. When BOD of sewage has reduced, the effluent is passed into ...G... . Here, A to G can be (a) A–sedimentation, B–centrifugation, C–BOD, D–Methanogen, E–Methanobacterium, F–water gas plant, G–settling tank (b) A–centrifugation, B–sedimentation, C–BOD, D–Methanogen, E–Methanococcus, F–biogas plant, G–sludge tank (c) A–filtration, B–centrifugation, C–BOD, D–Methanogen, E–Methanobacillus, F–gobar gas plant, G–filtre tank (d) A–filtration, B–sedimentation, C–BOD, D–Methanogen, E–Methanobacterium, F–sewage treatment plant, G–settling tank 41 In the sewage treatment, bacterial flocs are allowed to sediment in a settling tank. This sediment is called as (a) activated sludge (c) anaerobic sludge (b) primary sludge (d) secondary sludge 42 Given below is the flowchart of sewage treatment. Identify A, B, C, D and E and select the correct option. Primary sludge Primary treatment Effluent from primary settling tank Secondary treatment E D Sedimentation C 43 Primary sludge CBSE-AIPMT 2014 (a) possesses flocs of decomposer microbes (b) requires aeration for formation (c) involves little decomposition (d) forms during secondary sewage treatment 44 During sewage treatment, biogas is produced, which includes NEET 2013 (a) methane, hydrogen sulphide and carbon dioxide (b) methane, oxygen and hydrogen sulphide (c) hydrogen sulphide, methane and sulphur dioxide (d) hydrogen sulphide, nitrogen and methane 45 Microbes are used in I. primary treatment of sewage. II. secondary treatment of sewage. III. anaerobic sludge digesters. IV. production of biogas. Choose the correct option. (a) (b) (c) (d) I, II and III I, III and IV II, III and IV All of the above 46 The BOD test measures the rate of uptake of oxygen by microbes in water bodies. The greater BOD of sample water, indicates that (a) it is highly polluted (b) it is not polluted (c) it is moderately polluted (d) pollution level cannot be determined 47 Which of the following plans has been initiated by the A B Biogas formation (a) A–Small aeration tank, B–Microbial digestion, C–High BOD, D–Activated sludge, E–Aerobic sludge digesters (b) A–Large aeration tank, B–Mechanical agitation, C–Increased BOD, D–Activated sludge, E–Aerobic sludge digesters (c) A–Small aeration tank, B–Microbial digestion, C–Low BOD, D–Activated sludge, E–Anaerobic sludge digesters (d) A–Large aeration tank, B–Mechanical agitation, C–Reduced BOD, D–Activated sludge, E–Anaerobic sludge digesters Flocs Ministry of Environment and Forests to protect rivers from water pollution? (a) (b) (c) (d) Ganga action plan Yamuna action plan Both (a) and (b) None of the above www.mediit.in CHAPTER 10 > Microbes in Human Welfare TOPIC 4 ~ Microbes in Production of Biogas 48 The most flammable gaseous component of biogas is (a) (b) (c) (d) 249 methane, CO2 , H2 and H2 S methane CO2 , H2 and H2 S CO, methane and N2 (a) (b) (c) (d) A–Sludge, B–Dung + Water, C– Gas holder A–Dung + Water, B–Sludge, C–CH4 + CO2 A–Sludge, B–Gas holder, C–Dung + Water A–CH4 + CO2 , B–Dung + Water, C–Sludge 53 Study the following flowchart of biogas production 49 Methanogens are found in I. organic acid II. rumen of cattle III. butanal IV. anaerobic sludge and select the correct option for A, B and C. Stage III C B Choose the correct option. (a) I and II (c) II and IV (b) II and III (d) III and IV Organic acids Stage II A 50 Which of the following bacteria is present in the rumen of cattle? (a) Rhizobium (c) Methanobacterium production of biogas from the dung of ruminant NEET 2016 animals, include the (b) methanogens (d) halophiles 52 The diagram given below represents a typical biogas plant. Select the correct option for A, B and C, respectively. Gas C A Digester (b) biopesticide (d) bioweapon 56 In Bt cotton, the Bt toxin present in plant tissue as protoxin is converted into active toxin due to (a) (b) (c) (d) Fats Cellulose Hemicellulose (a) A–Methanogenic bacteria, B–Fermentative microbes, C–CO2 and hydrogen (biogas) (b) A–Anaerobic microorganisms, B–Methanococcus, C–CO2 and nitrogen (biogas) (c) A–Anaerobic microbes, B–Methanogenic bacteria, C–CO2 and methane (biogas) (d) A–Aerobic microorganism, B–Methanobacter, C–CO2 and methane (biogas) 54 Gobar gas generation technology in India was (a) A–Rural Bank of India, B–Khadi and Village Industries Commission (b) A–Indian Agricultural Research Institute, B–Khadi and Village Industries Commission (c) A–National Bank for Agriculture and Development, B–Indian Agricultural Research Institute (d) A–National Bank for Agriculture and Development, B–Khadi and Village Industries Commission Microbes as Biocontrol Agents and Biofertilisers 55 Bacillus thuringiensis is used as (a) biofungicide (c) biocontrol agent Proteins developed by the collaboration of ...A... and ...B... . Here, A and B refer to B TOPIC 5 ~ Soluble compounds or monomers (b) Azotobacter (d) Clostridium 51 The primitive prokaryotes responsible for the (a) thermoacidophiles (c) eubacteria Stage I alkaline pH of the insect gut CBSE-AIPMT 2015 acidic pH of the insect gut action of gut microorganisms the presence of conversion factors in insect gut 57 Cultivation of Bt cotton has been much in the news. The prefix Bt means (a) ‘Barium-treated’ cotton seeds (b) ‘Bigger thread’ variety of cotton with better tensile strength (c) produced by ‘biotechnology’ using restriction enzymes and ligases (d) carrying an endotoxin gene from Bacillus thuringiensis www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 250 58 Trichoderma species, free-living fungi, are present in root ecosystems are potentially useful as (a) (b) (c) (d) biopesticides biofertilisers methanogens vectors for genetic engineering agent in the treatment of plant disease? NEET 2019 (b) Anabaena (d) Trichoderma host specificity narrow spectrum applications effects on non-target insects utility in IPM programme (a) (b) (c) (d) NEET (Odisha) 2019 species-specific and symbiotic free-living and broad spectrum narrow spectrum and symbiotic species-specific and inactive on non-target organisms out biological control of pests/diseases using microbes? CBSE-AIPMT 2012 (a) Trichoderma sp., against certain plant pathogens (b) Nucleopolyhedrovirus against white rust in Brassica (c) Bt cotton to increase cotton yield (d) Ladybird beetle against aphids in mustard 63 Select the correct group of biocontrol agents. NEET 2019 (a) Trichoderma, Baculovirus, Bacillus thuringiensis (b) Oscillatoria, Rhizobium, Trichoderma (c) Nostoc, Azospirillum, Nucleopolyhedrovirus (d) Bacillus thuringiensis, Tobacco mosaic virus, Aphids 64 Organic farming includes use of fertilisers and pesticides of biological origin IPM (Integrated Pest Management) locally developed pest resistant varieties All of the above 65 The organisms which are used to enrich the nutrient quality of the soil are (a) bacteria (c) fungi (b) cyanobacteria (d) All of these 66 The most important of the symbiotic nitrogen-fixing bacteria, which forms nodules on the roots of legume plants is (a) Aspergillus (c) Penicillium (d) All of these 69 The symbiotic association of fungi with the roots of (a) eubacteria (c) mycorrhiza 62 Which one of the following is an example of carrying (a) (b) (c) (d) (b) I and III (c) II and III higher plants is called 61 A biocontrol agent to be a part of an integrated pest management should be nitrogen-fixing bacteria? I. Rhizobium II. Azospirillum III. Azotobacter Choose the correct option. (a) I and II 60 Baculoviruses (Nucleopolyhedrovirus) do not show (a) (b) (c) (d) Aspergillus and Rhizopus Rhizobium and Rhizopus Cyanobacteria and Rhizobium Aspergillus and Cyanobacteria 68 Which of the following belongs to free-living 59 Which of the following can be used as a biocontrol (a) Chlorella (c) Lactobacillus (a) (b) (c) (d) (b) Rhizobium (d) Streptococcus 67 Among the following pairs of microbes, which pair has both the microbes that can be used as biofertilisers? NEET (Odisha) 2019 (b) actinomycetes (d) lichen 70 The most common fungal partner of mycorrhiza belongs to genus (a) Azotobacter (b) Glomus (c) Azolla (d) Frankia 71 Which one of the following helps in absorption of phosphorus from soil? (a) Nostoc (b) Anabaena (c) Glomus (d) Yeast 72 Which of the following are the part or example of symbiotic mutualistic association? (a) Rhizobium (b) Mycorrhiza (c) Both (a) and (b) (d) Oscillatoria 73 Which of the following is cyanobacteria and fix atmospheric nitrogen? (a) Oscillatoria (b) Nostoc (c) Anabaena (d) All of these 74 Which of the following is common to Azospirillum, Anabaena, Nostoc and Oscillatoria? (a) N2 -fixer microbes (c) Both (a) and (b) (b) Prokaryotic organism (d) Eukaryotic organism 75 Which of the following serves as biofertiliser in paddy fields? (a) Anabaena (c) Nostoc (b) Azospirillum (d) Both (a) and (c) 76 Azolla is used as a biofertiliser because it AIIMS 2018 (a) (b) (c) (d) has association of mycorrhiza multiplies at faster rate to produce massive biomass has association of nitrogen-fixing Rhizobium has association of nitrogen-fixing cyanobacteria 77 A biocontrol agent used for pest butterfly caterpillars is (a) Trichoderma (c) Pseudomonas (b) Bacillus thuringiensis (d) Rhizobium 78 Select the group of organisms that are used as biofertilisers in organic farming. (a) Clostridium, Beijerinckia, Glomus and Anabaena (b) Trichoderma, Baculovirus and B. thuringiensis (c) Nostoc, Azolla pinnata and Tobacco mosaic virus (d) Penicillium, Streptococcus and Aspergillus www.mediit.in CHAPTER 10 > Microbes in Human Welfare 251 NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Direction (Q. No. 79-87) In each of the following questions, a statement of Assertion (A) is given by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 79 Assertion (A) Besides curdling of milk, LAB also 80 81 82 83 84 85 86 improve curd’s nutritional quality. Reason (R) LAB, when presents in human stomach, check disease causing microbes. Assertion (A) Biogas is used as fuel for cooking and lighting. Reason (R) It is considered as an ecofriendly and a pollution free source of energy. Assertion (A) Disadvantages of synthetic pesticides can be overcome by the use of biopesticides. Reason (R) Biopesticides control weeds and pest without causing any damage to living organisms. Assertion (A) Chemical pesticides are preferred over biopesticides. Reason (R) Chemical pesticides are mostly expensive, hazardous and pollute the atmosphere. Assertion (A) Leguminous plants are best preferred in rotation of crops. Reason (R) They have root nodules, which have nitrogen-fixing bacteria Clostridium. Assertion (A) Use of fertilisers greatly enhances crop productivity. Reason (R) Irrigation is very important in increasing crop productivity. Assertion (A) Beer and wine are called soft liquours. Reason (R) These beverages have lower percentage of alcohol. Assertion (A) An organ transplant patient is administered regular dose of cyclosporin-A. Reason (R) Cyclosporin-A is an immunosuppresant agent. 87 Assertion (A) Baculoviruses are broad spectrum insecticides. Reason (R) These viruses are excellent choices for biocontrol in an ecologically sensitive area for integrated pest management. II. Statement Based Questions 88 Which of the statement given below is incorrect? (a) Yeast is used in making bread and beverages is a prokaryotic fungus (b) Streptokinase is produced by Streptococcus and modified by genetic engineering is used as a clot buster (c) Lipases are added in detergent for removing oily stains from laundry (d) Pectinases are used in clearing of bottled fruit juices 89 Which of the following statements is incorrect? (a) Methanogens are present in human intestine and acts on fibrous component of food (b) Methanobacterium is a methanogenic bacteria (c) Methanogens play an important role in the nutrition of cattle (d) Gobar gas is rich in Methanobacterium 90 Which of the following statements is correct? (a) Ethanol is produced by the fermentation of malted cereals and fruit juices (b) Wine is produced without distillation (c) Saccharomyces is used for bread making (d) All of the above 91 Which of the following statement (s) is/are correct with regard to biocontrol agents? (a) Ladybird beetles and dragonflies are used to get rid of aphids and mosquitoes, respectively (b) Bacillus thuringiensis bacteria are used to control butterfly and caterpillars (c) Trichoderma species are used to control several plant pathogens (d) All of the above 92 Which of the following statements about methanogens is incorrect? NEET (Odisha) 2019 (a) They can be used to produce biogas (b) They are found in the rumen of cattle and their excreta (c) They grow aerobically and breakdown cellulose rich food (d) They produce methane gas www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 252 93 Which of the following statement is/are correct? (a) Biochemical Oxygen Demand (BOD) represents the amount of dissolved oxygen that would be consumed if all the organic matter in 1 L of water were oxidised by microorganism (b) Sewage water is treated to reduce its BOD (c) High value of BOD means the water is less polluted by organic matter (d) Both (a) and (b) 94 Benefits of mycorrhizae are indicated by which statement? (a) It shows resistance to root borne pathogen (b) It shows tolerance to salinity and pathogen (c) It helps in the overall increase in the plant growth and development (d) All of the above 95 Which of the following statements regarding baculoviruses as biocontrol agents are correct? (a) Baculoviruses are pathogens that attack insects and other arthropods (b) Most of these biocontrol agents belong to the genus Nucleopolyhedrovirus (c) They do not harm plants mammals, birds, fish and other non-target insects (d) All of the above 96 Consider the following statements about organic farming. Which of the statement given below is correct? (a) Organic farming promotes the use of crop rotations, cover crops and encourages balanced host/predator relationships (b) Integrated pest, weed management and soil conservation systems are valuable tools of an organic farm (c) Organic farming protects the environment, minimise soil degradation and erosion and decrease pollution (d) All of the above 97 Consider the following statements. Which of the statement given below is incorrect? (a) Microbes are also used to ferment fish, soybean and bamboo shoots to make foods (b) Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity coming from the microbe used (c) Trichoderma sp., free-living fungi, are present in root ecosystems where they act against several plant pathogens (d) Rhizobium is a symbiotic bacterium that lives in the stem of legumes 98 Which of the following statement(s) represents the main benefits of LAB? I. Increase vitamin-B12 amount, thus increasing nutrient quality of milk. II. Check disease causing microbes in stomach. Choose the correct option. (a) Only I (c) I and II (b) Only II (d) None of these 99 Consider the following statements. I. Antibiotics are chemical substances produced by some microorganisms which can kill or retard the growth of other disease-causing microorganisms. II. Penicillin was the first antibiotic discovered by Alexander Fleming (1928), while working on bacterium Staphylococcus aureus. III. The function of penicillin as an antibiotic was established by Ernst Chain and Howard Florey. Which of the statements given above are correct? (a) I and II (c) II and III (b) I and III (d) I, II and III 100 Which of the following statements are correct? I. Wine and beer are produced without distillation of fermented broth. II. Byproducts of alcoholic fermentation are CO2 and methane. III. Penicillium species is used for fermenting malted cereals to produce alcohol. Choose the correct option. (a) Only I (b) I and II (c) II and III (d) Only III 101 Sewage or municipal waste should not be directly passed into rivers, streams and other water bodies because I. it contains human excreta and other organic waste. II. it contains a number of pathogenic microbes. Which of the statement (s) given above is/are correct? (a) Only I (c) I and II (b) Only II (d) None of these 102 Consider the following statements. I. After primary treatment of sewage, all solids that settle down forms the primary sludge and the supernatant form the effluent. II. Spent slurry of biogas plant is used as fertiliser. Which of the statements given above are correct? (a) Only I (c) Only II (b) I and II (d) None of these 103 Consider the following statements about, secondary sewage treatment. I. In secondary treatment, useful aerobic microbes grow rapidly and form flocs. Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures. II. The growing microbes consume organic matter and thus, reduce the biochemical oxygen demand. When BOD of sewage has reduced, the effluent is passed into settling tank. www.mediit.in CHAPTER 10 > Microbes in Human Welfare III. In settling tank, the bacterial flocs settle and the sediment is called activated sludge. IV. A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed into large tanks called anaerobic sludge digesters. V. In the digesters, heterotrophic microbes anaerobically digest bacteria and fungi in sludge producing mixture of gases such as, carbon dioxide, nitrogen and carbon monoxide which form the biogas. Which of the statements given above are correct? (a) I, II, III and IV (c) II, III, IV and V (b) I, III, IV and V (d) I, II, III, IV and V 104 Consider the following statements about Bt. I. The bacteria Bacillus thuringiensis (Bt) are used to control butterfly catterpillars. II. Fresh spores of Bt are mixed with water and sprayed on to vulnerable plants such as brassicas and fruit trees. III. Insect larvae, after eating Bt ,are killed by the toxin released in their gut. IV. Bt toxin genes have been introduced into plants to provide resistance to pests. 253 (a) (b) (c) (d) Both statements I and II are correct Statement I is correct, but statement II is incorrect Statement I is incorrect, but statement II is correct Both statements I and II are incorrect 108 Read the following statements about disadvantages of chemical agents. I. Chemicals are toxic and harmful to human beings and animals. II. Chemicals pollute the environment and plants. III. Weedicides used to remove weeds also pollute the soil. Choose the correct option. (a) I, II and III (c) I and III (b) I and II (d) II and III 109 Read the following statements. AIIMS 2018 I. Colostrum is recommended for the newborns because it is rich in antigens. II. Chikungunya is caused by a Gram negative bacterium. III. Tissue culture has proved useful in obtaining virus-free plants. IV. Beer is manufactured by distillation of fermented grapes. Which of the statements given above are correct? How many of the statement(s) is/are correct ? (a) I, II and III (c) II, III and IV (a) Two (b) I, III and IV (d) I, II, III and IV 105 Which of the following statement(s) is correct? I. The dough, which is used for making bread, is fermented using Baker’s yeast, i.e. Saccharomyces cerevisiae. II. Production on an industrial scale, requires growing microbes in very large vessels called fermentors. III. The municipal wastewater is also called sewage. IV. It is necessary to treat sewage in Sewage Treatment Plants (STPs) to make it less polluting. Which of the statements given above are correct? (a) I and II (c) I, II and IV (b) Only III (d) I, II, III and IV 106 Which of the following is/are the approache(s) for biological farming? I. Familiarity with various life forms inhabiting the field. II. Gain knowledge about the life cycles, patterns of feeding and habitat of predators and pests. Choose the correct option. (a) Only I (c) I and II (b) Only II (d) None of these (b) One (c) Three (d) Four III. Matching Type Questions 110 Match the following columns. Column I (Organisms) Column II (Uses) A. Lactobacillus 1. Roquefort cheese B. Saccharomyces cerevisiae 2. Swiss cheese C. Propionibacterium shermanii 3. Bread D. Penicillium roqueforti 4. Milk into curd Codes A (a) 4 (c) 4 B 3 1 C 2 2 D 1 3 A (b) 3 (d) 1 B 2 4 C 1 3 D 4 2 111 Match the following columns. Column I Column II A. Azolla 1. Symbiotic N2-fixer B. Rotenone 2. Symbiotic association with N2 -fixing cyanobacteria C. Crotolaria juncea 3. Natural insecticide D. Frankia 4. Green manure Codes A (a) 2 (b) 2 (c) 2 (d) 1 B 3 4 1 3 107 Read the following statements and select the correct option. I. Biocontrol refers to the use of biological methods for controlling plant diseases and pests. II. Use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides. C 4 3 4 4 D 1 1 3 2 www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 254 112 Match the following columns. NEET 2016 Column I A. 1. Trichoderma B. Cyclosporin 2. Clostridium C. Statins 3. Aspergillus D. Butyric acid 4. Monascus Codes A (a) 3 (c) 1 B 1 4 Column I A. Symbiotic nitrogen-fixing bacteria B. Dragonflies C. Bacillus thuringiensis D. Free-living N 2-fixing bacteria Column II Citric acid C 2 2 D 4 3 A (b) 3 (d) 3 B 1 4 C 4 1 D 2 2 113 Match the following columns. Column I Column II Mycorrhiza 1. Nucleopolyhedrovirus B. Bacillus thuringiensis 2. Rhizobium C. Root nodules 3. Bt cotton D. Baculovirus 4. Phosphorus nutrition B 3 4 C 2 1 D 1 2 A (b) 3 (d) 4 B 2 1 C 1 2 D 4 3 114 Match the following list of microbes and their importance. CBSE-AIPMT 2015 A. Saccharomyces cerevisiae 1. Production of immunosuppressive agents B. Monascus purpureus 2. Ripening of Swiss cheese C. Trichoderma polysporum 3. Commercial production of ethanol D. Propionibacterium shermanii Codes A (a) 3 (b) 4 (c) 4 (d) 3 Codes A (a) 1 (c) 2 4. B 4 1 C 3 4 D 2 3 Column II 1. Mosquitoes 2. Rhizobium 3. Azotobacter 4. Butterfly, caterpillars A (b) 4 (d) 2 B 3 1 C 2 3 116 Match the following columns. A. Codes A (a) 4 (c) 3 115 Match the following columns. Production of bloodcholesterol lowering agents A. B. C. D. Column I Lactobacillus Saccharomyces cerevisiae Aspergillus niger Acetobacter aceti D 1 4 NEET 2019 1. 2. 3. 4. Column II Cheese Curd Citric acid Bread 5. Acetic acid Codes A (a) 2 (c) 2 B 4 1 C 3 3 D 5 5 A (b) 3 (d) 2 B 4 4 C 5 5 D 1 3 117 Match Column I (Antibiotic) with Column II (Source). AIIMS 2018 Column I Column II A. Fumagillin 1. Gliocladium virens B. Bacitracin 2. Streptomyces griseus C. Streptomycin 3. Bacillus polymyxa D. Viridin 4. Aspergillus fumigatus E. Polymixin 5. Bacillus licheniformis Codes B 4 3 2 1 C D 1 2 2 1 1 3 4 2 (a) (b) (c) (d) A 1 4 3 2 B 2 5 1 3 C 3 2 4 5 D 4 1 2 4 E 5 3 5 1 NCERT &NCERT Exemplar MULTIPLE CHOICE QUESTIONS NCERT 118 Which one of the following processes evidently prove that microbes release gases during metabolism? (a) Making of curd from milk (b) Rising of dough by yeast (c) Making of alcohol from malt (d) None of the above 119 Lactic acid bacteria are found in (a) milk (c) Both (a) and (b) (b) curd (d) None of these 120 Which of the following is antibiotic producing fungi? (a) Monascus (b) Peronospora (c) Penicillium (d) Rhizopus www.mediit.in CHAPTER 10 > Microbes in Human Welfare 121 Find out the incorrect pair from the following. (a) Biogas—Methanogens (b) Penicillium — Antibiotic (c) Curd — LAB (d) Citric acid — Trichoderma 122 Read the following and choose the incorrect statement. (a) Most biofertilisers are obtained from microbes (b) VAM is the example of biofertiliser giving organism (c) SCP is used as source of biofertiliser (d) None of the above NCERT Exemplar 123 The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is (a) vitamin-C (c) vitamin-B12 (b) vitamin-D (d) vitamin-E 124 Wastewater treatment generates a large quantity of sludge, which can be treated by (a) anaerobic digesters (c) chemicals (b) floc (d) oxidation pond (a) rumen of cattle (b) gobar gas plant (c) bottom of water-logged paddy fields (d) activated sludge 126 Match the following columns of bacteria and their commercially important products. Aspergillus niger 1. Lactic acid B. Acetobacter aceti 2. Butyric acid C. Clostridium butylicum 3. Acetic acid D. Lactobacillus 4. Citric acid A B C D (b) 2 4 3 1 (d) 4 1 3 2 127 Which one of the following alcoholic drinks is produced without distillation? (a) Wine 130 Big holes in Swiss cheese are made by (a) a machine (b) a bacterium that produces methane gas (c) a bacterium producing a large amount of carbon dioxide (d) a fungus that releases a lot of gases during its metabolic activities 131 The residue left after methane production from cattle dung is (a) burnt (c) used as manure (b) burried in land fills (d) used in civil construction 132 Methanogens do not produce (a) oxygen (c) hydrogen sulphide (b) methane (d) carbon dioxide 133 Activated sludge should have the ability to settle (a) be rapidly pumped back from sedimentation tank to aeration tank (b) absorb pathogenic bacteria present in wastewater, while sinking to the bottom of the settling tank (c) be discarded and anaerobically digested (d) absorb colloidal organic matter 134 Match the following list of bioactive substances and Column II (Products) A. Codes A B C D (a) 2 3 4 1 (c) 4 3 2 1 (c) Flocs would increase in size as anaerobic bacteria would grow around flocs (d) Protozoa would grow in large numbers quickly, so that it can 125 Methanogenic bacteria are not found in Column I (Bacterium) 255 (b) Whisky (c) Rum (d) Brandy 128 The free-living fungus Trichoderma can be used for (a) killing insects (b) biological control of plant diseases (c) controlling butterfly caterpillars (d) producing antibiotics 129 What would happen if oxygen availability to activated sludge flocs is reduced? (a) It will slow down the rate of degradation of organic matter (b) The centre of flocs will become anoxic, which would cause death of bacteria and eventually breakage of flocs their roles. Column I (Bioactive substances) Column II (Roles) A. Statin 1. Removal of oil stains B. Cyclosporin-A 2. Removal of clots from blood vessels C. Streptokinase 3. Lowering of blood cholesterol D. Lipase Codes A (a) 2 (c) 4 B 3 1 4. Immunosuppressive agent C 1 3 D 4 2 A (b) 4 (d) 3 B 2 4 C 1 2 D 3 1 135 The primary treatment of wastewater involves the removal of (a) dissolved impurities (c) toxic substances (b) stable particles (d) harmful bacteria 136 BOD of wastewater is estimated by measuring the amount of (a) total organic matter (b) biodegradable organic matter (c) oxygen evolution (d) oxygen consumption www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 256 137 The technology of biogas production from cow 139 Match the items in Column I and Column II and dung was developed in India largely due to the efforts of choose correct answer. (a) Gas Authority of India (b) Oil and Natural Gas Commission (c) Indian Agricultural Research Institute and Khadi and Village Industries Commission (d) Indian Oil Corporation A. B. C. D. Column I Ladybird Mycorrhiza Biological control Biogas Codes A (a) 2 (c) 4 138 Mycorrhiza does not help the host plant in (a) enhancing its phosphorus uptake capacity (b) increasing its tolerance to drought (c) enhancing its resistance to root pathogens (d) increasing its resistance to insects B 4 1 C 3 2 D 1 3 1. 2. 3. 4. A (b) 3 (d) 3 Column II Methanobacterium Trichoderma Aphids Glomus B 4 2 C 2 1 D 1 4 140 Which one of the following is not a nitrogen-fixing organism? (a) Anabaena (b) Nostoc (c) Azotobacter (d) Pseudomonas Answers Mastering NCERT with MCQs 1 (d) 16 (c) 31 (a) 46 (a) 61 (d) 76 (d) 2 (b) 17 (c) 32 (c) 47 (c) 62 (a) 77 (b) 3 (a) 18 (c) 33 (c) 48 (b) 63 (a) 78 (a) 4 (b) 19 (d) 34 (b) 49 (c) 64 (d) 5 (c) 20 (b) 35 (a) 50 (c) 65 (d) 6 (b) 21 (b) 36 (a) 51 (b) 66 (b) 7 (d) 22 (d) 37 (b) 52 (c) 67 (c) 8 (a) 23 (d) 38 (c) 53 (c) 68 (c) 9 (b) 24 (a) 39 (c) 54 (b) 69 (c) 10 (a) 25 (a) 40 (d) 55 (c) 70 (b) 11 (a) 26 (d) 41 (a) 56 (a) 71 (c) 12 (c) 27 (d) 42 (d) 57 (d) 72 (c) 13 (b) 28 (d) 43 (a) 58 (a) 73 (d) 14 (b) 29 (a) 44 (a) 59 (d) 74 (c) 15 (c) 30 (d) 45 (c) 60 (c) 75 (d) NEET Special Types Questions 79 (b) 80 (b) 81 (a) 82 (d) 83 (c) 84 (b) 85 (a) 86 (a) 87 (d) 88 (a) 89 (a) 90 (d) 91 (d) 92 (c) 93 (d) 94 (d) 95 (d) 96 (d) 97 (d) 98 (c) 99 (d) 100 (a) 101 (c) 102 (b) 103 (a) 104 (d) 105 (d) 106 (c) 107 (a) 108 (a) 109 (b) 110 (a) 111 (a) 112 (b) 113 (a) 114 (a) 115 (c) 116 (a) 117 (b) NCERT & NCERT Exemplar Questions 118 (b) 119 (c) 120 (c) 121 (d) 122 (c) 133 (a) 134 (d) 135 (b) 136 (d) 137 (c) 123 (c) 124 (a) 125 (d) 126 (c) 127 (a) 128 (b) 129 (b) 130 (c) 131 (c) 132 (a) 138 (d) 139 (b) 140 (d) Answers & Explanations 2 (b) Prions are the microscopic protein particles similar to a 7 (d) Heterotrophic bacteria are the most abundant life forms. virus, but lack nucleic acid. These are assumed to be the infectious agent, responsible for scrapie and certain other degenerative diseases of the nervous system. Many of them have a significant impact on humans, such as these are helpful in making curd from milk, e.g. Lactobacillus sp., and production of antibiotics, e.g. Streptomyces sp. 10 (a) The dough, which is used for making foods such as dosa, bread and idli are also fermented by bacteria. The puffed up appearance of dough is due to the production of CO2 gas by these bacteria. 12 (c) Swiss cheese is formed with the help of single strain of Propionibacterium shermanii. Its characteristic feature is the formation of large holes due to the production of a large amount of CO2 . 15 (c) Bioreactor is an essential equipment required for growing microbes on large scale, i.e. for the industrial production of enzymes, antibiotics, beverages, etc. These 3 (a) The nutritive medium for growing bacteria and many fungi in the laboratory is called culture media. This media contains all the essential requirements necessary for bacterial and fungal growth such as carbon, sugar, minerals, etc. The growth of microbes is visible as colonies that can be seen with the naked eyes. Such cultures are useful in studies on microorganisms. 5 (c) Lactobacillus is added to milk which converts lactose (sugar of milk) into lactic acid. Lactic acid causes coagulation and partial conversion of milk protein casein to calcium paracaseinate. These chemical changes in milk help in its conversion into curd, yoghurt and cheese. www.mediit.in 16 17 22 23 26 large vessels provide biologically active environment suitable for microbial production of such products. (c) Distilled spritis are alcoholic beverages in which the concentration of ethyl alcohol is more than the original fermented mixture which is obtained by distillation. These beverages are whisky, brandy and rum. Other beverages like wine and beer are produced without distillation. (c) An yeast, Saccharomyces cerevisiae, is used in the production of alcoholic beverages like wine, beer, whisky, brandy or rum. Beverages are generally formed by fermenting malted cereals and fruit juices with this yeast to produce ethanol or alcohol. (d) Penicillin was the first antibiotic to be discovered by Alexander Fleming (1928). The antibiotic was, however, commercially extracted by efforts of Ernst Chain and Howard Florey. Fleming, Chain and Florey were together awarded Nobel Prize in 1945, for this discovery. (d) Antibiotics have greatly improved our capacity to treat deadly diseases such as diphtheria (gal ghotu), whooping cough (kali khansi), plague, leprosy (kusht rog), which is used to kill millions of people all over the world. (d) Only option (d) is correctly matched. Other options are incorrectly matched and can be corrected as l l l Acetobacter aceti produces acetic acid. Methanobacterium produces methane. Penicillium notatum produces penicillin. 41 43 45 46 47 28 (d) Streptokinase produced by the bacterium 31 32 35 38 39 Streptococcus and modified by genetic engineering is used as a clot buster for removing clots from the blood vessels of patients who have undergone myocardial infarction leading to heart attack. (a) Statins are the commercial blood cholesterol lowering agents as these competitively inhibit the enzymes involved in cholesterol synthesis. These are obtained from the yeast, Monascus purpureus. (c) Option (c) is incorrectly matched in the table. It can be corrected as Butyric acid is produced by fermentative activity of the bacteria called Clostridium butylicum. It does not produce lipase. Lipase is obtained from Candida albicans. Rest of the options contain correct matches. (a) Primary treatment is the physical removal of large and small particles from sewage through filtration and sedimentation. (c) In sewage treatment, suspended solids are removed during primary treatment. It is also known as physical treatment. It consists of shredding, churning, screening and sedimentation. Sequential filtration removes floating and large suspended solids. (c) In the biological treatment of sewage, flocs are formed. These are masses of bacteria associated with fungal filaments to form a mesh-like structure. The 48 49 51 53 growing microbes consume organic matter and thus reduce the Biochemical Oxygen Demand (BOD) and lowers the level of pollutants. (a) In the sewage treatment, when Biochemical Oxygen Demand (BOD) of sewage has reduced, the effluent is passed into settling tank. Here, the bacterial flocs settle and the sediment thus formed is called activated sludge. (a) Option (a) is correct. Primary sludge possesses flocs of decomposer (aerobic) microbes, which consume a major part of the organic matter in the effluent to reduce the BOD. (c) Primary treatment does not involve microbes. It is the physical removal of large and small particles from sewage. However, secondary treatment of the effluent from the primary settling tank is purely a biological treatment involving microbial activity. Further, in the anaerobic sludge digesters, heterotrophic microbes anaerobically digest bacteria and fungi in the sludge producing mixture of gases such as methane, hydrogen sulphide and CO2 , which form biogas. Thus, microbes are used in secondary treatment, anaerobic sludge digesters and biogas production. (a) BOD is a measure of the organic matter present in water. Thus, greater the value of BOD in a sample of water, more will be its polluting potential. This indicates that the water body will be highly polluted. (c) In order to protect the major rivers of India from water pollution, the Ministry of Environment and Forests, has initiated development of the sewage treatment plants under the National River Conservation Authority, so that only treated sewage may be discharged in the rivers, e.g. Ganga Action Plan (GAP), Yamuna Action Plan (YAP), Satluj Action Plan and Gomti Action Plan. (b) The major component of biogas is methane (about 50-68%), and it is highly inflammable. The other gaseous components of biogas are carbon dioxide (25-35%), hydrogen (1-7%) and rarely hydrogen sulphide. (c) Methanogens, particularly Methanobacterium, are the anaerobic bacteria, which breakdown cellulosic material to produce methane, CO2 and H2 . These are found in the anaerobic sludge in sewage treatment plants and rumen (a part of stomach) of cattle. These play an important role in nutrition. (b) Methanogens are a group of obligate anaerobic ancient or primitive bacteria (prokaryote). These are involved in methanogenesis and produce methane gas (biogas) from the dung of ruminant animals. (c) The correct option for A, B and C is (c) as Anaerobic microbes, methanogenic bacteria, CO 2 and methane (biogas), respectively. In stage - I, anaerobic microorganisms, (A) bring about enzymatic breakdown of complex organic compounds into simple soluble compounds or monomers. In stage -II, monomers are converted into organic acids by fermentating microbes. Answers & Explanations 257 CHAPTER 10 > Microbes in Human Welfare www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 258 55 56 57 59 60 61 Answers & Explanations 62 63 In stage -III, organic acids are acted upon by methanogenic bacteria (B) to produce methane rich mixture of gases called biogas (C). (c) Bacillus thuringiensis is a soil bacterium used as biocontrol agent that can control infestations by insect pests such as butterfly, caterpillars, ants, moths, etc. Some strains of these bacteria can kill animal and plant parasitic nematodes, snails, protozoans, etc. (a) The Bt toxin is an inactive protoxin, which gets activated due to the alkaline pH of the insect gut. Proteins are solubilised and proteolytically processed when exposed to alkaline pH and thus are activated. The toxins then attack the gut cells of the insect, creating holes in the lining casusing lysis and death of the insect. (d) In Bt cotton, Bt means carrying an endotoxin gene from Bacillus thuringiensis. Specific Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into several crop plants such as cotton, corn, etc. The toxin is coded by a gene named cry and imparts resistance to a wide range of insect pests. (d) Trichoderma can be used as a biocontrol agent of several plant pathogens. It is a filamentous soil fungus having mycoparasitic activity. On the other hand, Anabaena helps in nitrogen-fixation, Lactobacillus helps in the production of organic acid, e.g. lactic acid and Chlorella is a single cell protein, which acts as food supplement. (c) Baculoviruses (Nucleopolyhedrovirus) do not show effect on non-target insects. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. These have been known to shown no negative impacts on plants, mammals, birds, fish or even on non-target insects. (d) For a biocontrol agent to be a part of an Integrated Pest Management (IPM) programme, it should be species-specific and inactive or have no negative impacts on non-target organisms like plants, mammals, birds, fish and even another non-target insects. It should kill only targeted insects/pests (organisms). (a) Option (a) gives an example of biological pest/disease control being carried out by microbes. Trichoderma species are effective biocontrol agents of several plant pathogens. They are free-living fungi that are very common in the root ecosystems. (a) The correct group of biocontrol agents is given by option (a), i.e. Trichoderma, baculovirus and Bacillus thuringiensis. l l l Baculoviruses are pathogens that attack insects and other arthropods. Most of baculoviruses used as biocontrol agent belong to the genus–Nucleopolyhedrovirus. Trichoderma is extensively used against pathogenic fungi which causes soil-borne diseases. Bacillus thuringiensis secretes toxin cyrstals which kill the insect larvae. 64 (d) Organic farming includes several methods to 66 67 68 69 71 73 75 76 77 79 80 enhance soil fertility. In such farming, methods of biological origin are used, e.g. biopesticide, biofertilisers, IPM (Integrated Pest Management), locally developed pest resistant varieties, green manure, etc. (b) Rhizobium is a soil bacterium that fixes nitrogen in symbiotic association with root nodules of legumes (Fabaceae). Rhizobium requires a plant host, as it cannot independently fix atmospheric nitrogen. (c) Cyanobacteria and Rhizobium can be used as biofertilisers. Biofertilisers are the organisms that enrich the nutrient quality of the soil. Whereas, Aspergillus and Rhizopus are not used as biofertilisers. (c) Azospirillum and Azotobacter are free-living nitrogen-fixing bacteria. These bacteria fix atmospheric nitrogen in the soil and make it available for the higher plants. On the other hand, Rhizobium is the symbiotic nitrogen-fixing bacterium. (c) A mycorrhiza is a symbiotic (mutually beneficial) association between a fungus and the roots of a vascular (higher) plant. These are important components of soil life and soil chemistry. (c) Genus–Glomus forms mycorrhiza with roots of higher plants. It is a fungus which helps in nutrient uptake from soil, mainly aiding the absorption of phosphorus. ( d ) Nostoc, Anabaena and Oscillatoria are all cyanobacteria which fix atmospheric nitrogen and increase the organic matter of the soil through photosynthetic activity. (d) Nostoc and Anabaena are cyanobacteria, which serve as important biofertilisers in paddy fields. These fix atmospheric nitrogen and increase the organic matter of soil through their photosynthetic activity. These also increase the soil fertility by adding organic matter to the soil. (d) Azolla is a pteridophyte and it is used as a biofertiliser because it has association with a nitrogen-fixing cyanobacteria called Anabaena azollae. (b) Bacillus thuringiensis is the most effective biocontrol agent for insect pests such as butterfly caterpillars. Spores of this bacterium produce a toxic insecticidal protein called Cry. These proteins enter the host’s body and reach gut where on activation they kill the host by lysis. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The correct explanation is LAB also improve curd’s nutritional quality during coagulation of milk by increasing the content of vitamin-B12 and other nutrients. It is present in curd and also checks the growth of disease causing microbes in stomach and other parts of digestive tract in humans. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. The correct explanation is as follows www.mediit.in 259 CHAPTER 10 > Microbes in Human Welfare 82 83 84 85 86 87 88 89 92 93 97 100 Baculoviruses are species-specific narrow spectrum insecticides. These features make them an excellent choice for conservation of beneficial insects during integrated pest management programme in an ecologically sensitive area. (a) The statement in option (a) is incorrect. It can be corrected as Yeast is used in making bread and beverages is a type of eukaryotic fungus. Rest of the statements are correct. (a) The statement in option (a) is incorrect and can be corrected as Methanogens are present in the rumen (a part of stomach) of cattle (runminant) where it acts on the cellulosic content to yield a methane rich mixtrue of gases. Rest of the statements are correct. (c) The statement in option (c) is incorrect and can be corrected as Certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with CO 2 and H 2 . These bacteria are collectively called methanogens and one such example is Methanobacterium. Rest of the statements in other options are correct. (d) The statements in options (a) and (b) are correct, while the statement in option (c) is incorrect. It can be corrected as High value of BOD means that the water body is highly polluted by organic matter. (d) The statement in option (d) is incorrect and can be corrected as Rhizobium is a symbiotic bacterium that lives in the root nodules of legumes and fixes atmospheric nitrogen. Rest of the statements are correct. (a) Statement I is correct. The correct form of the incorrect statements II and III are l l The byproducts of alcoholic fermentation are CO 2 and ethanol (not methane). Saccharomyces cerevisiae is used for fermenting malted cereals to produce alcohol. Penicillium on the other hand is used for the production of the antibiotic, penicillin. 103 (a) Statements I, II, III and IV are correct, but statement V is incorrect and it can be corrected as In the digesters, heterotrophic microbes anaerobically digest the bacteria and fungi in the sludge. During this digestion, bacteria produce mixture of gases such as methane, hydrogen sulphide and CO2 , which form biogas. 106 (c) Both the approaches given in statements I and II are correct for biological farming. An important part of the biological farming approach is to become familiar with the various life forms that inhabit the field, predators as well as pests and also their Answers & Explanations 81 Biogas is used as fuel for heating, cooking, lighting because it is flammable. It is an alternative of firewood, kerosene, etc., and acts as an ecofriendly and a pollution free source of energy. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Synthetic pesticides are chemicals which have several disadvantages such as their high cost, long term pollution, toxicity and tendency to accumulate in living organisms, etc. These disadvantages can be overcome by the use of biopesticides that are simple components of biological origin because these cause no damage or toxicity in living organisms. (d) Assertion is false, but Reason is true. Assertion can be corrected as Chemical pesticides are not preferred over biopesticides. This is because chemical fertilisers are generally more expensive and hazardous in nature. These unnecessarily pollute the natural resources like soil and water over a long time. (c) Assertion is true, but Reason is false. Reason can be corrected as Leguminous crops are grown in rotation of crops. These plants have the ability to fix atmospheric nitrogen to form nitrogen compounds through the help of certain bacteria, like Rhizobium, present in their root nodules. In rotation of crops, leguminous crops like pulses, beans, peas, groundnut and Bengal gram are sown in between the seasons of cereal crops like wheat, maize and pearl millet. These are leguminous plants when grown alternately with non-leguminous plants restore the fertility of the soil. (b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. Use of fertilisers greatly enhances crop productivity by addition of nitrogen, phosphorus and potassium to the soil. Irrigation practices are also helpful in enhancing the crop yield by fulfilling the demand of water in crops. In this way, both fertilisers and irrigation are equally important for high crop yield. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. Beer and wine are called as soft liquours because these are produced without undergoing distillation and have lower percentage of alcohol content as compared to hard liquours like rum, whisky, brandy, etc. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. An organ transplant patient is kept on a regular dose of cyclosporin-A to reduce the risk of transplant rejection. Cyclosporin-A is used as immunosuppessive agent in organ transplanted patients to inhibit the activation of T-cells and interferes with the destruction of non-self cells. It thus, increases the chances of graft being accepted recepient’s body. (d) Assertion is false, but Reason is true. Assertion can be corrected as www.mediit.in Master The NCERT > BIOLOGY (Vol-II ) 260 life cycles, patterns of feeding and the habitats that they prefer. This will help to develop appropriate means of biocontrol. 109 (b) Only one statement, i.e. statement III is correct. Rest statements are incorrect and can be corrected as l l l Colostrum is the first breastmilk of mother, which contains antibodies (especially IgA). It provides immunity to infants against various pathogens. Chikungunya is caused by chikungunya virus. Beer is manufactured without distillation, by fermentation of barley malt by yeast. 118 (b) The process given in option (b) evidently proves that microbes release gases during metabolism. Rising of dough occurs by the activity of yeast metabolism. It happens due to the bubble formation because of the release of CO2 . It is the easiest way to understand that yeast releases CO2 . 119 (c) Lactic Acid Bacteria (LAB) found in curd and especially, Lactobacillus casei are abundantly found in raw milk. These are commonly used as probiotics. 121 (d) Option (d) shows the incorrect pair and can be corrected as Citric acid–Aspergillus niger. Rest of the options contain the correct pairs. 122 (c) The statement in option (c) is incorrect and can be corrected as Single Cell Protein (SCP) is a source of protein, e.g. Spirulina products. Rest of the statements are correct. 123 (c) Microorganisms such as Lactobacillus and others commonly called Lactic Acid Bacteria (LAB) grow in milk and convert it into curd. LAB improve nutritional quality of milk and curd by increasing the content of vitamin-B12 . 124 (a) Wastewater treatment generates a large quantity of sludge, which is further treated by anaerobic digesters. These are large heated tanks in which various methanogenic anaerobic bacteria digest the bacteria and fungi present in the sludge. Answers & Explanations 125 (d) Methanogenic bacteria (that produce methane) are not found in activated sludge. The microbes present in the activated sludge are aerobic bacteria that grow rapidly and form flocs. On the other hand methanogens are the anaerobic bacteria present in anaerobic sludge digesters. 127 (a) Wine is an alcoholic drink produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth. 128 (b) Trichoderma species are free-living fungi that are very common in root ecosystems or soil. These are effective biocontrol agents of several plant pathogens. 129 (b) Activated sludge microorganisms need oxygen as they oxidise wastes to obtain energy for growth. Thus, if oxygen availability to activated sludge flocs is reduced, insufficient oxygen (anoxic) conditions will slow down or kill off aerobic microorganisms, make facultative organisms work less efficiently and ultimately lead to the breakage of flocs. 130 (c) The large holes in ‘Swiss cheese’ are due to the production of a large amount of CO2 by a bacterium named, Propionibacterium shermanii. 132 (a) In the digesters (during secondary treatment of waste water), heterotrophic microbes like methanogens anaerobically digest biodegradable waste in sludge producing mixture of gases such as methane, hydrogen sulphide and CO2 which form the biogas. Thus, O2 is not produced by methanogens. 133 (a) Activated sludge should have the ability to settle quickly, so that it can be ready pumped back from sedimentation tank to aeration tank because a small part of the activated sludge is used as inoculum in the aeration tank. 135 (b) The primary treatment of wastewater involves physical removal of both larger and small particles (stable particles) from the sewage through filtration and sedimentation. These are removed in stages, initially, floating debris is removed by sequential filtration. Then, the grit (soil and small pebbles) are removed by sedimentation. 138 (d) Mycorrhiza does not help the host plant in increasing its resistance to insects. Infact, plants having such associations show resistance only to root-borne plant pathogens, tolerance to salinity and drought and an overall increase in plant growth and development. 140 (d) Pseudomonas is a denitrifying bacterium, which converts ammonia and nitrates into free nitrogen, i.e. to liberate free nitrogen in the environment through nitrogen cycle. Therefore, it is not a nitrogen-fixing organism. Other options (a), (b) and (c) show nitrogen-fixing organisms. www.mediit.in CHAPTER > 11 Biotechnology : Principles and Processes NEET Å Å Å KEY NOTES Biotechnology is the technique of using living organisms or enzymes from organisms to produce products and processes useful to humans. Biotechnology deals with the large scale production and marketing of products such as enzymes, insulin or antibiotics, etc., that are of importance to mankind. The European Federation of Biotechnology (EFB) has given a definition of biotechnology as, the integration of natural science and organisms cells, parts thereof and molecular analogues for products and services’. Å Å Principles of Biotechnology Following two core techniques gave birth to modern biotechnology Å Genetic engineering It is the alteration of the chemistry of genetic material (DNA/RNA), introduce these into host organisms and consequently change the phenotype of the host organism. Å Bioprocess engineering It is the maintenance of sterile conditions in order to enable the growth of only desired microbes or eukaryotic cells in large quantities for the production of antibiotics, enzymes, hormones, vaccines, etc. Å Å Genetic Engineering Å Å It is the deliberate modification of an organism’s DNA, using various techniques. This altered DNA (recombinant DNA) is then introduced into host organisms to change their phenotype. This is followed by growing this genetically modified cell in large quantities, by maintaining sterile environment, for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc. Å Techniques of genetic engineering include construction of recombinant DNA, gene cloning and gene transfer. These techniques allow the isolation and introduction of a set of desirable genes without introducing undesirable genes into the target organism. Origin of replication (ori) is a specific DNA sequence in the chromosome which can initiate DNA replication. The foreign DNA introduced into the host genome has to be linked the origin of replication in the host chromosome for the gene to be able to multiply. This is also known as cloning which involves making multiple identical copies of any template DNA. If the foreign gene is not linked to the ori sequence it may not be able to multiply. In 1972, the first recombinant DNA was constructed by Stanley Cohen and Herbert Boyer. They isolated the antibiotic resistance gene by cutting out a piece of DNA from a plasmid (autonomously replicating circular extrachromosomal DNA) of Salmonella typhimurium. The cutting of DNA at specific locations become possible with the help of restriction enzymes (molecular scissors). The cut pieces of DNA were then linked with the plasmid DNA using DNA ligase enzyme. These plasmids act as vectors to transfer the piece of DNA attached to it into the host organism. This makes a new circular autonomously replicating DNA created in vitro and is known as the recombinant DNA. The recombinant DNA is transferred into Escherichia coli, a bacterium closely related to Salmonella, where it replicates using the new host’s DNA polymerase enzyme and makes multiple copies of itself. It also produces multiple copies of the antibiotic resistance gene in the new host (E. coli). This process is called as cloning of antibiotic resistance gene in E. coli. www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 262 Å There are three basic steps involved in genetically modifying an organism n Identification of DNA with desirable genes. n Introduction of the identified DNA into the host. Types of Restriction Enzyme Å The restriction enzymes can be of three types, on the basis of their chemical and physiological properties. Type II Enzyme Type III Enzyme Bifunctional enzyme with 3 subunits Separate endonuclease and methylase Bifunctional enzyme with 2 subunits Recognition site Genetic engineering or recombinant DNA technology can be accomplished only if we have the key tools, i.e. restriction enzymes, polymerase enzymes, ligases, vectors and the host organism. Bipartite and asymmetrical (e.g. TGAC and TGCT) Short sequence Asymmetrical (4-6 bp), often sequence of 5-7 palindromic bp Cleavage site Non-specific >1000 bp Same as or 24-26 bp from recognition site close to downstream of recognition site recognition site 1. Restriction Enzymes Restriction and Mutually exclusive methylation Separate reactions Simultaneous ATP needed for restriction Yes No Yes Mg 2+needed for restriction Yes Yes Yes Commonly used in Random cutting and fragments making Gene cloning Gene cloning n Maintenance of introduced DNA in the host and transfer of the DNA to its progeny. Tools of Recombinant DNA Technology Å Å Å Å In the year 1963, the two enzymes responsible for restricting the growth to bacteriophage in E. coli were isolated. One of these added methyl group to DNA, while the other cut DNA. The latter was called restriction endonuclease. The first restriction endonuclease, i.e. Hind II was isolated by Smith Wilcox and Kelley in 1968. Hind II always cut the DNA at specific base sequences, i.e. of six base pairs. Apart from Hind II, more than 900 restriction enzymes have been isolated from over 230 strains of bacteria. Protein structure Examples of Restriction Enzymes Names Sources Sites Types of End Hpa I Haemophilus parainfluenzae 5 ′ GTT - AAC 3 ′ 3 ′ CAA - TTG 5 ′ Blunt Ssp I Sphaerotilus species 5 ′ AAT - ATT 3 ′ 3 ′ TTA - TAA 5 ′ Blunt Pst I Providencia stuartii 5 ′ CTGCA - G 3 ′ 3 ′ G - ACGTC 5 ′ Sticky Hind II 5 ′ GTC - GAC 3 ′ 3 ′ CAG - CTG 5 ′ Blunt Restriction enzymes belong to a larger class of enzymes called nucleases, which are of the following two types Haemophilus influenzae Eco RI Escherichia coli 5 ′ G - AATTC 3 ′ 3 ′ CTTAA - G 5 ′ Sticky Hae III Haemophilus aegyptius 5 ′ GG - CC 3 ′ Blunt Bam HI Bacillus amyloliquefaciens 5 ′ GGAT - CC3 ′ 3 ′ CCTA - GG 5 ′ n Å Type I Enzyme Naming of restriction enzyme proceeds in a way that the first letter of the name comes from the genus and the second two letters come from the species of prokaryotic cell. Roman number following the names indicate the order in which the enzyme were isolated from that strain of bacteria, e.g. Eco RI comes from E. coli RY13. n Å Features Exonucleases, which remove nucleotides from the ends of the DNA (either 5′ or 3′) in one strand of duplex. Endonucleases make cuts at specific positions within the DNA by inspecting the length of a DNA sequence. Once finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar phosphate to backbones. These restriction enzymes recognise a palindromic nucleotide sequence in the DNA and cut both the strands of DNA at that point. Palindrome in the DNA is a sequence of base pairs that reads same on the two strands when orientation of reading is kept the same. For example, the following sequence reads the same on the two strands whether read in 5′→ 3′ direction or 3′→ 5′ direction. 5′−GAATTC−3′ 3′−CTTAAG−5′ NEET 3 ′ CC - GG 5 ′ Sticky Å Restriction enzymes cut the strand of DNA, a little away from the center of the palindrome sites, but between the same two bases on the opposite strands. These staggered cuts leave single-stranded portions at both the ends. These are referred to as sticky ends. Å There are other restriction enzymes which cut both the DNA strands at the same place so that single-stranded pieces are not left in the ends. Such ends are called blunt ends. Å Stickiness is the chemical ability of a DNA molecule to base pair with any other DNA molecule that has also been cut by the same restriction enzyme. It means it will have KEY NOTES www.mediit.in 263 CHAPTER 11 > Biotechnology : Principles and Processes Å Å Å The DNA fragments separated and cut out from the gel and extracted from gel piece. This step is known as elution. same sequence hanging unpaired. This stickiness of the ends facilitates the action of the enzyme DNA ligase. Å DNA ligase (molecular binder) enzymes help in sealing the gaps in DNA fragments by forming a phosphodiester bond between the adjacent 3′ — OH and 5′ phosphate terminals, thereby joining nicks in double-stranded DNA. 2. Cloning Vectors Lysing enzymes/Lyases enzymes are used for the isolation of DNA from cells, e.g. lysozyme is used to digest the bacterial cell wall for the extraction of cellular DNA. Protease, lipase and other degrading enzymes come in this category. Alkaline phosphatase catalyse the removal of 5′ phosphate group from the DNA and thus, modify the terminus of DNA. Action of restriction enzyme Å Å Å Å Eco RI cuts the DNA between bases G and A only when the sequence GAATTC is present in the DNA Foreign DNA The enzyme cuts both DNA strands at the same site Vector DNA Å Å Eco RI Sticky end Sticky end DNA fragments join at sticky ends Å Plasmids and bacteriophages are used as cloning vectors. This is because plasmids and bacteriophages have the ability to replicate within the bacterial cell independent of chromosomal DNA. Bacteriophages have very high copy numbers of their genome within the bacterial cells. But in case of plasmids, some may have only one or two copies per cell whereas others may have 15-100 copies per cell. Cloning vectors use the machinery of bacterial cell to replicate and thereby, increase the copy number (make clones) of the DNA inserted into them. These help easy linking of foreign DNA and allow the selection of recombinants (bacterial cells that have picked up recombinant plasmid) from non-recombinants (those who have not). All vectros have four special features that are required to facilitate cloning into a vector. Origin of replication (ori) is the sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence also controls the copy number of the linked DNA. Selectable marker helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants. Transformation is the procedure through which a piece of DNA is introduced into a host bacterium. Normally, antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers. Cloning sites are used to link the alien DNA. The vector needs to have cloning or recognition sites for the commonly used restriction enzymes. The presence of more than one recognition sites within the vector will generate several fragments and complicate the gene cloning. n Recombinant DNA n Steps in the formation of recombinant DNA by action of restriction endonuclease enzyme Eco RI Separation and Isolation of DNA Fragments Å Separation of restriction fragments from each other can be done by gel electrophoresis. Å An electric field is applied and these fragments are forced to move through a viscous gel of agarose (a natural polymer extracted from sea weeds). Å Since, DNA fragments are negatively charged (because of their phosphate groups) they will move towards the positively charged pole, i.e. anode. Å Smaller fragments move faster and bigger ones move slowes, but they all separate out (according to their size) into bands that can be identified later by staining. Å The staining of DNA bands can be done with a compound known as ethidium bromide followed by exposure to UV radiation. Bright orange coloured bands of DNA are visible. Å Eco RI Pvu I Pst I Cla I Hind III Bam HI ampR tetR pBR322 ori Sal I rop Pvu II E. coli cloning vector pBR322 showing restriction sites (Hind III, EcoRI, BamHI, Sal I, Pvu II, Pst I, Cla I), ori and antibiotic resistance genes (amp R and tet R ). rop codes for the proteins involved in the replication of the plasmid NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 264 n n n n n Å Å Å The ligation of foreign DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. It can be done at the Bam HI site of tetracycline resistance gene in the vector pBR 322. In this case, the recombinant plasmids will lose tetracycline resistance due to the insertion of foreign DNA but can still be selected out from non-recombinant ones by plating the transformants on a medium containing ampicillin. The recombinants will grow in ampicillin containing medium but not on that containing tetracycline. But, non-recombinants will grow on the medium containing both the antibiotics. Other selectable markers can differentiate recombinants from non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate. In this, recombinant DNA is inserted within the coding sequence of an enzyme, β-galactosidase. This results into inactivation of the gene synthesis of this enzyme and referred to as insertional inactivation. The presence of a chromogenic substrate gives blue coloured colonies if the plasmid in the bacteria does not have an insert and if the colonies have inserted plasmid, such colonies are recombinants and show no colouration. Vectors for cloning genes in plants and animals A pathogen of several dicot plant is able to deliver a piece of DNA, i.e. ‘T-DNA’ to transform normal plant cells into a tumour cells and disect these tumour cells to produce the chemicals required by the pathogen. Similarly, retrovirus in animals have the ability to transform normal cells into cancerous cells. Å Recombinant DNA is directly injected into the nucleus of an animal cell, using a microsyringe. This is known as microinjection. Å Plant cells are bombarded with high velocity microparticles of gold or tungsten coated with DNA in a method known as biolistics or gene gun. Å Some pathogens that naturally infect a cell can be ‘disarmed’ (by eliminating their harmful gene) and then allowed to infect the cell, carrying the desired recombinant DNA into the host. Processes of Recombinant DNA Technology Å Recombinant DNA technology involves various steps in a specific sequence such as isolation of the desired genetic material (DNA), cutting of DNA at specific locations, isolation of desired DNA fragment, amplification of gene of interest by PCR, ligation of DNA fragments into a vector, insertion of recombinant DNA into host cell, culturing the host cells in a medium at large scale and interaction of the desired product. Isolation of the Genetic Material (DNA) Å The genetic material, DNA needs to be in pure form, free from other macromolecules, for restriction enzymes to be able to act on it. Following are the steps n The tumour inducing (Ti) plasmid of Agrobacterium tumefaciens has now been modified into a cloning vector which is able to use the mechanisms to deliver genes of our interest into a variety of plants. n Similarly, retroviruses can be disarmed and used to deliver desirable genes into animal cells. n 3. Competent Host Å Å Since, DNA is a hydrophilic molecule, it cannot pass through cell membrane that has hydrophobic ends both on the inside and outside. Hence, various artificial means have to be used to make the cells competent to take up foreign DNA. Bacteria are treated with a specific concentration of a divalent cation, such as calcium, which makes the cell membrane more permeable. Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 42°C (heat shock) and then putting them back on ice. This makes the bacterial cell competent to take up the recombinant DNA. NEET Cell wall needs to be broken to release DNA. For this, the bacterial cells/plant or animal tissue are treated with enzymes such as lysozyme (bacteria), cellulase (plant cells), chitinase (fungus). Histones and other proteins have to be removed by treatment with proteases and the RNA can be removed by treatment with ribonuclease. With the addition of chilled ethanol, purified DNA precipitates out. This can be seen as collection of fine threads in the suspension and removed out by spooling. Amplification of Gene of Interest Using PCR Å PCR stands for Polymerase Chain Reaction, a method of amplifying the fragments of DNA. This method can make multiple copies of even a single DNA fragment or the gene of interest in a test tube. The reaction mixture requires n n Double-stranded DNA fragment (gene of interest). Primers, i.e. small chemially synthesised oligonucleotides that are complementary to the regions of this DNA. KEY NOTES www.mediit.in 265 CHAPTER 11 > Biotechnology : Principles and Processes n Å The special thermostable DNA polymerase (isolated from the bacterium, Thermus aquaticus) that does not denature and remains active even at high temperatures. With each round of reaction, the DNA quantity gets amplified. If the process of replication of DNA is repeated many times the segment of DNA can be amplified to approximately billion times, i.e. 1 billion copies are made. Region to be amplified 5′ 3′ 3′ dsDNA 5′ Denaturation Heat 5′ 3′ 5′ 3′ 5′ The foreign gene gets expressed under appropriate conditions. After having the cloned gene of interest and having optimised conditions to induce the expression of the target protein, large scale production can be carried out. Å If any protein encoding gene is expressed in a heterologous host, the product protein is called a recombinant protein. Å The cells harbouring cloned genes of interest may be grown on a small scale in the laboratory. The cultures may be used for extracting the desired protein. The cells can also be multiplied in a continuous culture system, wherein the used medium is drained out from one side, while fresh medium is added from the other to maintain the cells in their physiologically most active growth phase, i.e. log/exponential phase. This type of culturing method produces a larger biomass leading to higher yields of desired protein. For large scale production, bioreactors are used and culture can be processed. Å Bioreactors are large vessels (100-1000 L capacity) in which raw materials are biologically converted into specific products, individual enzymes, etc., using microbial, plant, animal or human cells. These are specially designed to provide optimal conditions of temperature, pH, substrate, salts, vitamins, oxygen, etc., for achieving the desired production levels. Å Bioreactors can be of two types–continuous culture system and non-continuous culture system (Batch culture). The two variants of bioreactors are sparged tank bioreactor and simple stirred-tank bioreactor. A stirred tank reactor is usually cylindrical or with a curved base to facilitate the even mixing and oxygen availability throughout the bioreactor. It is the most commonly used type of bioreactor. Primers annealing 5′ 5′ DNA polymerase (Taq polymerase + deoxynucleotides) 3′ 5′ 3′ 5′ 3′ Å 3′ 3′ 3′ 5′ Obtaining the Foreign Gene Product Extension 30 cycles Amplified (~ 1 billion times) Polymerase Chain Reaction (PCR) : Each cycle has three steps, i.e. Insertion of Recombinant DNA into the Host Cell/Organism Å There are several methods of introducing the ligated DNA into recipient cells. Recipient cells after making them competent to receive take up DNA present in their surrounding. Å So, if a recombinant DNA bearing gene for resistance to an antibiotic (e.g. ampicillin) is transferred into E. coli cells, the host cells are transformed into ampicillin-resistant cells. Å If we spread the transformed cells on agar plates containing ampicillin, only transformants will grow and untransformed recipient cells will die. Å Since, due to ampicillin resistance gene, one is able to select a transformed cell in the presence of ampicillin. The ampicillin resistance gene in this case is called a selectable marker. Downstream Processing The steps of downstream processing are separation and purification of the gene product, i.e. the functional protein, formulating it with suitable formulation. Such formulations undergo clinical trials to determine product quality. The downstream processing and quality control testing vary from product to product. NEET KEY NOTES www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 266 Mastering NCERT MULTIPLE CHOICE QUESTIONS TOPIC 1 ~ Principles of Biotechnology and Restriction Enzymes 1 The controlled use of biological agents, such as live organisms or enzymes from organisms to produce products and processes useful to humans is called as (a) biochemistry (c) biotechnology (b) molecular biology (d) microbiology 2 The techniques/processes that are included under biotechnology are (a) in vitro fertilisation (c) synthesising a gene (b) correcting a defective gene (d) All of these 3 EFB stands for (a) (b) (c) (d) traditional biotechnology modern molecular biotechnology DNA fingerprinting Both (a) and (b) 5 The two main techniques that gave birth to modern biotechnology are I. bioprocess engineering. II. genetic engineering. III. human genome engineering. IV. molecular biology. Choose the correct option. (b) I and III (c) II and IV (d) II and III altering genetic material sequencing genetic material studying genetic material None of the above 7 The specific sequence of DNA that initiate replication of alien DNA in rDNA technology is called as (a) initiation sequence (c) origin of DNA (b) origin of replication (d) initiation of DNA 8 Autonomously replicating circular extra-chromosomal DNA is (a) vector (c) plasmid (b) Salmonella typhimurium (d) Yeast 10 The first recombinant DNA was constructed by (a) Stanley Cohen (b) Herbert Boyer (c) Temin and Baltimore (d) Both (a) and (b) 11 The linking of antibiotic resistance gene with the plasmid vector became possible with (b) RNA ligase (d) RNA polymerase organism are given below randomly. I. Identification of DNA with desirable genes. II. Transfer of the DNA to its progeny. III. Maintenance of introduced DNA in the host. IV. Introduction of identified DNA into the host. Which of the following represents the correct sequence of steps? (a) I, II, III and IV (c) III, IV, II and I (b) I, IV, III and II (d) I, III, IV and II 13 The key tools required for the recombinant DNA 6 Genetic engineering techniques include (a) (b) (c) (d) (a) E. coli (c) Bacillus thuringiensis 12 The different basic steps of genetically modifying an encompasses (a) I and II done by using the native plasmid of (a) DNA ligase (c) DNA polymerase European Federation of Biotechnology Eurasian Federation of Biotechnology East Asia Federation of Biotechnology Ethiopian Federation of Biotechnology 4 The definition of biotechnology given by EFB (a) (b) (c) (d) 9 The construction of the first recombinant DNA was (b) capsid (d) bacteriophage technology are I. restriction enzymes II. polymerase enzymes III. ligases IV. vector V. host organism Select the correct option. (a) I, II and III (c) I, II, III and V (b) I, III, IV and V (d) I, II, III, IV and V 14 The enzymes, commonly used in genetic engineering are (a) (b) (c) (d) restriction endonuclease and polymerase endonuclease and ligase restriction endonuclease and ligase ligase and polymerase 15 The first restriction endonuclease to be discovered is (a) Hind III (b) Hind II (c) Eco RI (d) Eco RII 16 Which of the following is a restriction endonuclease? CBSE-AIPMT 2015 (a) Protease (b) DNase I (c) RNase (d) Hind II www.mediit.in 267 CHAPTER 11 > Biotechnology : Principles and Processes 17 The restriction enzyme responsible for the cleavage of following sequence is 5′ – G T C G A C 3′ 3′ – C A G C T G 5′ (a) Alu I (b) Bam HI (c) Hind II (a) single-stranded RNA (b) double-stranded DNA (c) single-stranded DNA (d) double-stranded RNA 28 Restriction endonuclease binds to DNA and cuts two (d) Eco RI 18 How many restriction enzymes are isolated till now? (a) 920 (b) 940 (c) 900 (d) 230 19 Number of bacterial strains from which restriction enzymes have been isolated. (a) 230 (b) 250 (c) 200 (d) 220 20 In the naming of restriction enzymes, the first letter of the name is derived from ..... A .... and next two letters from the ..... B ..... and fourth letters from the name of ..... C .... of .... D .... from which the enzymes are extracted. A to D in the statement can be (a) (b) (c) (d) A genus species genus species B species genus species genus C strain strain variety variety D bacteria bacteria eukaryote eukaryote 21 There is a restriction endonuclease called Eco RI. What does ‘co’ part in it stands for? (a) Coelom (c) coli (b) Strain of bacterium (d) Colon 22 The Roman number following the name of restriction enzyme indicate (a) order in which enzyme is isolated from strain of bacteria (b) number of enzyme (c) order of enzyme (d) None of the above 23 Restriction enzyme belongs to which class of enzymes? (a) Ligases (c) Nucleases enzymes can be used for (b) viral DNA only (d) eukaryotic DNA only 25 An enzyme catalysing the removal of nucleotides from ends of DNA is (a) DNA ligase (c) exonuclease strands of double helix at specific points in their (a) sugar-phosphate backbone (b) hydrogen bond (c) glycosidic bonds (d) None of the above 29 Special sequence in the DNA recognised by restriction endonuclease is called (a) (b) (c) (d) restriction nucleotide sequence palindromic nucleotide sequence recognition nucleotide sequence All of the above 30 Palindrome sequences (a) read opposite on two strands (b) read specific sequence in opposite direction (c) read same on two strands when orientation of reading is same (d) read opposite on two strands when orientation of reading is same 31 Restriction enzyme cuts the DNA strand a little away from the centre of palindrome site between (a) same two bases on same strand (b) same two bases on opposite strand (c) opposite bases on same strand (d) opposite bases on opposite strand 32 The foreign DNA and the vector is cut with the (a) two different enzymes (b) same restriction enzymes (c) DNA ligase (d) Both (a) and (b) 33 How many fragments will be generated, if a linear (b) Exonucleases (d) Proteases 24 In a genetic engineering experiment, restriction (a) bacterial DNA only (c) any DNA fragment 27 Restriction endonuclease enzymes are used to cut NEET (Odisha) 2019 (b) endonuclease (d) protease 26 Restriction endonucleases are enzymes which (a) make cuts at any position within the DNA molecule (b) recognise a specific nucleotide sequence for binding and then cleaves both the strands of DNA (c) restrict the action of the enzyme DNA polymerase (d) remove nucleotides from the ends of the DNA molecule DNA molecule is digested with a restriction enzyme having 4 recognition sites on the DNA? (a) 3 (c) 4 (b) 5 (d) 6 34 How many fragments will be generated, if a closed circular DNA molecule is digested using a restriction enzyme having six recognition sites on the DNA? (a) 4 (b) 6 (c) 7 (d) 5 35 A foreign DNA and plasmid cut by the same restriction endouclease can be joined to form a NEET 2016 recombinant plasmid using (a) Eco RI (c) polymerase III (b) Taq polymerase (d) ligase 36 Which is also called molecular glue? (a) DNA gyrase (c) DNA ligase JIPMER 2019 (b) DNA helicase (d) DNA polymerase www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 268 37 Study the given diagram and identify the enzymes A and B involved in steps I and II. Vector DNA Foreign DNA Enzyme A Step I Sticky end (a) A–Restriction endonuclease, B–Restriction exonuclease, C–RNA ligase, D–Transformation (b) A–Restriction endonuclease, B–Restriction endonuclease, C–DNA ligase, D–Transformation (c) A–Restriction exonuclease, B–Restriction endonuclease, C–DNA polymerase, D–Transduction (d) A–Restriction endonuclease, B–Restriction endonuclease, C–DNA polymerase, D–Transformation 40 The cutting of DNA by ……… results in the Sticky end Enzyme B DNA fragments join at sticky ends Step II Step II DNA ligase DNA ligase DNA polymerase DNA polymerase 38 Which of the following option (s) is not correct regarding Eco RI enzyme? (a) centrifugation (b) polymerase chain reaction (c) electrophoresis (d) restriction mapping 42 Which of the following techniques is most (a) Chromatography (c) RFLP (b) PCR (d) Gel electrophoresis 43 Agarose is extracted from 39 The flowchart given below represents the process of recombinant technology. Identify A to D in the given process. Vector DNA (plasmid) B (enzyme) A (enzyme) endonucleases in a chemical reaction can be separated by NEET 2013 commonly used to separate DNA molecules by size? (a) Restriction endonuclease enzyme (b) Isolated from Escherichia coli RY13 (c) Cuts at specific position within the DNA (d) None of the above Foreign DNA (a) restriction endonucleases (b) exonuclease (c) endonuclease (d) anhydro L-galactose 41 DNA fragments generated by the restriction Recombinant DNA Step I (a) Eco RI (b) Alu I (c) Hind II (d) Restriction endonuclease fragments of DNA. Choose the appropriate option. (a) sea weeds (c) Ephedra (b) blue-green algae (d) Sargassam 44 What is the criterion for DNA fragments movements on agarose gel during gel electrophoresis ? NEET 2017 (a) The larger the fragment size, the farther it moves (b) The smaller the fragments size, the farther it moves (c) Positively charged fragments move to farther end (d) Negatively charged fragments do not move 45 In gel electrophoresis, restriction enzyme digested DNA is loaded in wells near C (joining enzyme) (a) anode (c) centre of gel (b) cathode (d) any where in the gel 46 Having become an expert on gel electrophoresis, Recombinant DNA molecule D (process) E. coli (Cloning host) Cells divide you are asked to examine a gel for a colleague. Where would you find the smallest fragments of DNA? (a) Near the positive electrode, farthest away from the wells (b) Near the negative electrode, close to the wells (c) Near the top, near the negative pole (d) Near the middle they tend to slow-down after the first few minutes www.mediit.in 269 CHAPTER 11 > Biotechnology : Principles and Processes 47 The DNA fragments separated on an agarose gel can be visualised after staining with NEET 2017 light, they are seen as (a) yellow coloured bands (b) orange coloured bands (c) blue coloured bands (d) Both (a) and (b) (a) bromophenol blue (b) acetocarmins (c) aniline blue (d) ethidium bromide 48 In gel electrophoresis, the separated DNA fragments are visualised after staining the DNA with EtBr followed by exposure to …. . Choose the appropriate option. (a) Infrared radiation (c) γ-rays 49 When the DNA fragments are observed under UV (b) UV-radiation (d) Radiowave 50 In gel electrophoresis, the separated bands of DNA are cut out and extracted from the gel piece. This step is called (a) elution (b) origin of replication (c) competency (d) transformation TOPIC 2 ~ Cloning Vectors and Competent Host 51 In recombinant DNA technique, the term vector refers 58 Identify A, B, C and D in the given diagram of E. coli cloning vector pBR322. to a (a) donor DNA, it is identified and picked up through electrophoresis (b) plasmid transfers DNA into host cell (c) collection of entire genome in the form of plasmid (d) enzyme, cuts the DNA at specific sites A Cla I B Pst I D tetR pBR322 52 Which of the following is used in recombinant DNA technique? (a) (b) (c) (d) Sal I C Cell wall of virus Gene which produces capsid of virus Bacteriophage Capsid of virus 53 During ‘gene cloning’ which is called a gene taxi? (a) Vaccine (c) Bacteria Hind III Pvu I (b) Plasmid (d) Protozoa 54 Which of the following is not a feature of the plasmids? CBSE-AIPMT 2015 (a) Circular structure (b) Transferable (c) Single-stranded (d) Independent replication rop Pvu II (a) A–Eco RI, B–Bam HI, C–ori, D–ampR (b) A–ampR, B–ori, C–Bam HI, D–Eco RI (c) A–ori, B–Bam HI, C–Eco RI, D–ampR (d) A–Bam HI, B–Eco RI, C–ampR, D–ori 59 The given figure is the diagrammatic representation of the vector pBR322. Which one of the given options correctly identifies its certain component(s)? Eco RI Cla I Hind III Pvu I 55 Which vector can clone only a small fragment of DNA? CBSE-AIPMT 2014 (a) Bacterial artificial chromosome (b) Yeast artificial chromosome (c) Plasmid (d) Cosmid Bam HI Pst I ampR tetR pBR322 Sal I ori rop 56 The DNA used as a carrier for transferring a fragment of foreign DNA into a suitable host is called (a) cloning vector (c) gene carrier (b) vehicle DNA (d) All of these 57 Which of the following is a plasmid vector? (a) pBR322 (c) SaI I (b) Bam II (d) Eco RI Pvu II (a) ori–original restriction enzymes (b) rop–reduced osmotic pressure (c) Hind III, Eco RI–selectable markers (d) ampR, tetR–antibiotic resistance genes www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 270 60 The two antibiotic resistance genes on vector pBR322 are for NEET (Odisha) 2019 (a) ampicillin and tetracycline (b) ampicillin and chloramphenicol (c) chloramphenicol and tetracycline (d) tetracycline and kanamycin 71 Agrobacterium tumefaciens delivers a piece of DNA help in replication of linked DNA control copy number of the linked DNA help in selecting recombinants Both (a) and (b) into dicot plant. The piece of DNA is called as (a) rDNA transformed cells is known as NEET 2017 NEET (Odisha) 2019 (a) help in eliminating the non-transformants, so that the transformants can be regenerated (b) identify the gene for a desired trait in an alien organism (c) select a suitable vector for tansformation in a specific crop (d) mark a gene on a chromosome for isolation using restriction enzyme 64 If recombinant DNA carrying antibiotic resistance gene (e.g. ampicillin) is transferred into E. coli cell, the host cell is transformed into ampicillin resistant cells. The ampicillin resistant gene in this case is called a (a) vectors (c) selectable marker (b) plasmid (d) cloning sites 65 The presence of more than one recognition site within vector will lead to the (a) (b) (c) (d) generation of several fragments generation of one fragment generation of half fragment None of the above 66 The recognition site for Bam HI in pBR322 is present in (a) ampicillin resistant site (b) tetracycline resistant site (c) ori site (d) rop site 67 When an alien DNA is ligated in tetracycline resistant gene, the recombinant (a) (b) (c) (d) (d) cDNA change normal cells into (b) vector (d) structural gene 63 A selectable marker is used to (b) T-DNA (c) mDNA 72 Retroviruses in animals including humans are able to 62 A gene, whose expression helps to identify (a) selectable marker (c) plasmid differentiated on the basis of (a) production of blue colour (b) production of no colour (c) production of red colour (d) production of green colour 61 The function of ori in a vector is (a) (b) (c) (d) 70 Recombinant colonies in insertional inactivation are become tetracycline resistant will loose tetracycline resistant will remain same None of the above 68 The method(s) that is/are used to differentiate (a) germ cell (c) cosmid 73 The plasmid of Agrobacterium tumefaciens that is now modified as a cloning vector is (a) Pi-plasmid (c) Ti-plasmid 69 In insertional inactivation, the recombinant DNA is (a) Auxin gene (c) Cytokinin gene (b) Virulent gene AIIMS 2019 (d) Auxin and cytokinin gene 75 Why foreign DNA cannot pass through cell membrane? (a) (b) (c) (d) DNA is hydrophobic DNA is hydrophilic DNA is rich in proteins DNA is heavy 76 The treatment of host cell with divalent cation leads to the (a) change in permeability of DNA (b) increased efficiency with which DNA enters the bacterium (c) decreased efficiency with which DNA enters the bacterium (d) change in permeability of host 77 The method which is used to introduce recombinant DNA into animal cell? (a) Gene gun method (c) Biolistic method (b) Changing permeability of host (d) Microinjection 78 Which of the following methods(s) is used to introduce foreign DNA into plant host cells? (a) Gene gun method (c) Elution (b) Gel electrophoresis (d) Extension 79 For transformation, microparticles coated with DNA to be bombarded with gene gun are made up of CBSE-AIPMT 2012 (a) silver or platinum (c) silicon or platinum (b) platinum or zinc (d) gold or tungsten 80 DNA transfer with high velocity micro particles is inserted within the coding sequence of present in (a) β-galactosidase (c) restriction enzyme (a) biolistics (c) tissue culture (b) tetracycline resistant gene (d) ampicillin resistant gene AIIMS 2019 (b) cosmid (d) None of these 74 In Ti-plasmid, which of the following is removed? recombinants and non-recombinants is/are (a) antibiotic affected gene (b) insertional inactivation (d) Both (a) and (b) (c) gene cloning (b) cancerous cells (d) vector JIPMER 2018 (b) hybridisation (d) vegetative propagation www.mediit.in 271 CHAPTER 11 > Biotechnology : Principles and Processes TOPIC 3 ~ Processes of Recombinant DNA Technology 81 The different steps involved in the process of recombinant DNA technology are given below randomly? Arrange these in correct order. I. Extraction of the desired gene product. II. Amplification of the gene of interest. III. Isolation of a desired DNA fragment. IV. Ligation of the DNA fragment into a vector. V. Insertion of recombinant DNA into the host. Correct order is (a) I, II, III, IV and V (c) II, IV, V, III and I (b) III, II, IV, V and I (d) I, IV, V, III and II 82 In bacterial cells, the membrane is digested with the help of enzyme (a) cellulase (c) chitinase (b) lysozyme (d) lipase (b) protease (d) cellulase (b) extension (d) All of these Reaction (PCR) is (b) chitinase (d) protease can be achieved by treatment with CBSE-AIPMT 2015 (a) Thiobacillus ferroxidans (b) Bacillus subtilis (c) Pseudomonas subtilis (d) Thermus aquaticus 92 The correct order of steps in Polymerase Chain 85 DNA precipitation out of a mixture of biomolecules (a) (b) (c) (d) 90 The Taq polymerase enzyme is obtained from (a) denaturation (c) annealing 84 Proteins are removed by treatment with (a) ribonuclease (c) cellulase (a) small chemically synthesised oligonucleotides of about 10-18 nucleotides that are complementary to the region of template DNA (b) chemically synthesised oligonucleotides of about 10-18 nucleotides that are not complementary to the region of template DNA (c) the double-stranded DNA that need to be amplified (d) specific sequences present on recombinant DNA 91 A single PCR amplification cycle involves 83 RNA is removed by the treatment with (a) ribonuclease (c) chitinase 89 Primers are NEET 2019 chilled ethanol methanol at room temperature chilled chloroform isopropanol (a) (b) (c) (d) NEET 2018 Denaturation, Extension, Annealing Annealing, Extension, Denaturation Extension, Denaturation, Annealing Denaturation, Annealing, Extension 93 The below diagram refer to PCR. Identify the steps A, B, C and D. Select the correct option. Region to be amplified 86 Purified DNA ultimately precipitates out and this can be seen as collection of fine threads in the suspension as seen in the figure. It refers to 5′ 3′ 3′ dsDNA 5′ Heat 5′ 3′ 5′ A 3′ 5′ Primers B 5′ 3′ 3′ 3′ 5′ (a) DNA Spooling (c) DNA recognition (b) DNA digestion (d) DNA bands 87 Chimeric DNA is (a) gene clone (c) transposon AIIMS 2019 (b) recombinant DNA (d) vector shuttle 88 Polymerase Chain Reaction (PCR) needs (a) DNA template (c) Taq polymerase 3′ (b) Primers (d) All of these 3′ 5′ 5′ 3′ C 5′ 30 cycles D (a) A–Denaturation at 94-96°C, B–Annealing at 40-60°C, C–Extension through Taq polymerase at 72°C, D–Amplified www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 272 (b) A–Annealing at 94-96°C, B–Denaturation at 40-60°C, C–Extension through Taq polymerase at 72°C, D–Amplification (c) A–Extension through Taq polymerase at 40-60°C, B–Amplification, C–Denaturation at 40-60°C, D–Annealing at 94-96°C (d) A–Amplification, B–Extension through Taq polymerase at 40-60°C, C–Denaturation at 40-60°C, D–Annealing at 94-96°C 94 If a recombinant DNA bearing gene for ampicllin resitance is transferred into E. coli and the host cells are spread on agar plates containing ampicillin, then AIIMS 2018 (a) both transformed and untransformed recipient cells will die (b) both transformed and untransformed recipient cells will grow (c) transformed recipient cells will grow and untransformed recipient cells will die (d) transformed recipient cells will die and untransformed recipient cells will grow 95 Protein encoding gene which is expressed in heterologous host is (a) foreign protein (c) recombinant protein (b) heterologous protein (d) alien protein TOPIC 4~ Bioreactors and Downstream Processing 96 In continuous culture system, (a) (b) (c) (d) used medium is drained out biomass produced is high no new medium is added Both (a) and (b) 97 A bioreactor (a) (b) (c) (d) is hybridoma cultures products containing radioactive isotopes cultures for the synthesis of new chemicals cultures large volume of living cells 98 Stirred-tank bioreactors have been designed for the (a) purification of the product (b) addition of preservatives to the product (c) availability of oxygen throughout the biorector (d) ensuring anaerobic conditions in the culture vessel A B C D E (a) Motor Foam breaker Sterile air (b) Foam breaker Sterile air Steam for Acid/Base Motor sterilisation for pH control (c) Acid/base Motor for pH control Foam breaker (d) Sterile air Steam for Foam sterilisation breaker Steam for Acid/base sterilisation for pH control Sterile air Steam for sterilisation Motor Acid/base for pH control 101 Identify the correct match for the given apparatus. 99 Stirred-tank bioreactors are advantageous over shake flasks because they (a) provide high temperature and pH (b) provide better aeration and mixing properties (c) do not allow the entry of CO2 (d) are easy to operate 100 Simple stirred-tank bioreactor is given below. Identify A, B, C, D and E. E A B D Flat bladed impeller Culture broth C Apparatus Functions (a) Gene gun Vectorless direct gene transfer (b) Column chromatograph Separation of chlorophyll pigments (c) Sparged tank bioreactor Carry out fermentation process (d) Respirometer Finding out rate of respiration www.mediit.in 273 CHAPTER 11 > Biotechnology : Principles and Processes 102 The components of a bioreactor are I. an agitator system. II. an oxygen delivery system. III. foam control system. IV. temperature control system. V. pH control system. VI. sampling ports to withdraw cultures periodically. 103 The process of separation and purification of expressed protein before marketing is called (a) (b) (c) (d) 104 Which of the following is not a component of Choose the correct option. downstream processing? (a) I, II, III, IV and V (c) I, II, III, IV and VI (a) Separation (c) Preservation (b) II, IV, V and VI (d) All of these NEET 2017 upstream processing downstream processing bioprocessing post-production processing NEET 2016 (b) Purification (d) Expression NEET SPECIAL TYPES QUESTIONS I. Assertion and Reason ■ Direction (Q. No. 105-113) In each of the following questions, a statement of Assertion (A) is given followed by corresponding statement of Reason (R). Of the statements, mark the correct answer as (a) If both A and R are true and R is the correct explanation of A (b) If both A and R are true, but R is not the correct explanation of A (c) If A is true, but R is false (d) If A is false, but R is true 105 Assertion (A) Biotechnology deals with techniques 106 107 108 109 that use living organism to produce products useful for humans. Reason (R) It uses only a unicellular organism. Assertion (A) Maintenance of sterile environment is essential for manufacture of biotechnological products. Reason (R) This is to enable growth of desired prokaryotic or eukaryotic cells. Assertion (A) Origin of replication is an essential part of a vector. Reason (R) Ori is responsible for initiating replication. Assertion (A) Foreign DNA and vector DNA cut with the help of ligase. Reason (R) Ligase acts by forming phosphodiester bonds. Assertion (A) In gel electrophoresis, DNA fragments are separated. Reason (R) DNA is negatively charged, so it moves towards anode under electric field. 110 Assertion (A) Restriction endonucleases are also called ‘molecular scissors’. Reason (R) When fragments generated by restriction endonucleases are mixed, they join together due to their sticky ends. 111 Assertion (A) All endonucleases cut DNA at specific sites. Reason (R) Endonucleases were discovered from viruses. 112 Assertion (A) The tumour inducing plasmid (Ti plasmid) of Agrobacterium tumefaciens acts as a cloning vector in recombinant DNA technology. Reason (R) The Ti plasmid which is used in the mechanisms of delivering genes to a cell remains pathogenic. 113 Assertion (A) Use of chitinase enzyme is necessary for isolation of DNA from fungal cells. Reason (R) Fungal cell wall is made up of chitin and chitinase is able to digest it. II. Statement Based Questions 114 Which one is a true statement regarding DNA polymerase used in PCR? CBSE-AIPMT 2012 (a) It is used to ligate introduced DNA in recipient cells (b) It serves as a selectable marker (c) It is isolated from a virus (d) It remains active at high temperature 115 Following statements describe the characteristics of the enzyme restriction endonulease. Identify the incorrect statement. NEET 2019 (a) The enzyme binds DNA at specific sites and cuts only one of the two strands www.mediit.in Master The NCERT > BIOLOGY (Vol-II) 274 (b) The enzyme cuts the sugar-phosphate backbone at specific sites on each strand (c) The enzyme recognises a specific palindromic nucleotide sequence in the DNA (d) The enzyme cuts DNA molecules at identified position within the DNA 116 Which of the following statement is incorrect? (a) Nucleic acid is fragmented by nucleases (b) Construction of recombinant DNA involves cleaning DNA segments with endonuclease and rejoining with ligase (c) Genetic engineering is making artificial limbs and diagnostic instruments (d) Ti plasmid transforms cells of plants 117 Which of the following statement is incorrect? (a) DNA being a hydrophilic molecule cannot pass through cell membranes (b) Agrobacterium tumefaciens delivers a piece of DNA known as ‘Z-DNA’ which transforms normal plant cells into tumour cells and directs these tumour cells to produce chemicals against pathogens (c) Retrovirus, adenovirus, papillomavirus are also now used as cloning vectors in animal because of their ability to transform normal cells into cancerous cell (d) In genetic engineering, DNA from different sources are cut with the same restriction enzymes so that both DNA fragments have same kind of sticky ends 118 Consider the following statements and select the correct option. (a) A soil inhabiting plant bacterium, Agrobacterium tumefaciens, a pathogen of several dicot plants is able to transfer a piece of DNA known as T-DNA (b) The T-DNA causes tumours (c) Tumour formation is induced by Ti plasmid (d) All of the above 119 Which of the following statement is incorrect? (a) Each restriction endonuclease recognises a specific palindromic nucleotide sequence (b) Specific base sequence is known as recognition sequence (c) Restriction enzymes cannot cut DNA (d) Restriction enzymes belong to enzymes called nucleases 120 Which of the following statement is incorrect? (a) EcoRI cuts the DNA between bases G and A (b) Making multiple identical copies of any template DNA is called cloning (c) pBR322 is a natural plasmid (d) Agrobacterium tumefaciens is a natural genetic engineer 121 Choose the incorrect statement . (c) Copy number refers to the number of copies of plasmid present in a cell (d) Copy number of plasmid varies from 50-100 per cell 122 Which of the statements given is incorrect? (a) In microinjection method, foreign DNA is directly injected into the nucleus of animal cell by using microneedles (b) Microinjection method is used in oocytes,
