STUDY MATERIAL FOR CLASS XII
SESSION 2010-2011
BIOLOGY
K.V. OCF, SEC-29-B, CHANDIGARH.
How to use this study material
This study material is a supplement material to the NCERT textbook. It is neither a guide nor a
refresher.
The teachers can prepare the master card by taking the important topics/points/concepts /terms etc
from this study material for the quick revision for the exam.
The material can also be used during the study camp by taking the important questions from
the study material as mentioned in the level 1, 2& 3 assignments depending on the level of the
student.
The material can also be used during the crash course by doing the revision of those topics by
the teachers depending upon the topics given in starting or at the end of the chapter.
Systematic revision of the different topics according to their level of difficulty & importance.
Details of the concept to be mastered by every child of class XII with concepts and
exercises of NCERT Book.
Symbols used
* Important Questions
* * Very Important Questions
* * * Very-very
Important Questions
S.NO
CHAPTER
Concepts
1
Reproduction In
Organisms
Types of reproduction
A) Asexual reproduction
B) Sexual reproduction, phases
and events in sexual
reproduction
Degree of
imp.
*
**
Ref. NCERT text book.: page nos
Common errors
NCERT text book xii fig . 1.2(a)
(b) fig. 1.3, 1.4 page 5-8
fail to differentiate
asexual reproductive
structureszoospores,
conidium, gemules
etc.
NCERT book p – 15 - 19 ex q
2,6,9,13,15,18
differentiation in
monoecious &
diocious
2
Sexual
Reproduction In
Flowering Plants
1. Pre fertilization: structures and
events
(i) stamens microsporangium &
pollengrain microsporogenesis
(ii) pistil megasporangium
( ovule) embryosacmegasporogenesis
2) pollination
(i) autogamy , xenogamy,
geitnogamy
(ii) agents of pollination
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NCERT book fig 2.2. 2.3 , 2.5 p –
21 – 23
NCERT book fig 2.7(d) 2.8 p –
24 – 27
NCERT book
p – 27 – 28
NCERT book
p – 31 – 33
NCERT book p – 34 fig 2.12.
no. of cells in mature
pollengrains
no. of cells & nuclei
in embryo sac , role
of synergids
self incompatibility
triple fusion
(iii) out breeding devices
(iv) pollen pistil interaction
3. Double fertilization
4. Post fertilization : structures &
events – endosperm , embryo, seed
5. Apomixis - polyembryony
3
Human
Reproduction
1 male reproductive system
(i) diagram & description
(ii) parts of male reproductive
system (structure)
(iii) functions of parts of system
(iv) accessory ducts
(v) accessory glands
2. Female reproductive system
(i) diagram & description
(ii) parts of female reproductive
system (structure)
(iii) functions of parts of system
(iv) accessory ducts
(v) uterus & its layers
(vi) mammary glands
3 gametogenesis
(i) spermatogenesis & diagram
(ii) stages of spermatogenesis with
names of cells & no of
chromosomes
(iii) structure of sperm (diagram)
(iv) functons of each part of sperm
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*
**
(c,d,e)
fig – 2.13, 2.14, 2.15
p – 35 NCERT
free nuclear &
cellular endosperm,
embryo of monocot
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p – 38 NCERT
fail to differentiate
apomixes ,
parthenocarpy
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*
NCERT P – 43 , FIG 3.1 (B)
NCERT P – 43-44
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NCERT P – 43-44
Exact Location &
Function Of Leydig
Cells & Sertoli Cells
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NCERT P – 44- 46 , FIG 3.3 (B)
-DO-
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NCERT P – 44-46
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NCERT P – 44
NCERT P – 46
NCERT P – 47
NCERT P – 47 FIG – 3.2 & 3.5 ,
3.8 (a) P – 49
Page no 47
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Fig 3.6, page no 48
page no 48
Exact Stage Where
Meiosis I & Ii Occurs
During
Gametogenesis As
Well As The Ploidy
Of Cells At Each
Stage Of
& organelles
(v) composition of semen
4 oogenesis
i)structure and description
ii) development of follicles
iii) stages with names of cells and
no. of chromosomes with events
iv) significance of polar bodies
5 menstrual cycle
(i) menarche and menopause
(ii) phases of menstrual cycle with
diagram
(iii) role of hormones in cycle
6 fertilization and implantation
(i) structure of ovum
(ii) cleavage- formation of morula
and blastula
(iii )implantation- meaning, stage
and site
(iv) sex determination in humans
(v) three germ layers
7 pregnancy and embryonic
development
(i) placenta as endocrine gland
(ii) embryo and extra-embryonic
layers
8 parturition
(i) meaning
(ii) foetal ejection reflex
(iii) Role of hormones
9 lactation
Gametogenesis
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page no 48
Fig 3.7 ,Fig 3.8(b)
Page no 48-49
Page no48-49
Difficulty in relating
different stages of
oogenesis with
different life stages.
Page no48-49
Page no – 49, 51
Fig 3.9
Co-relation of levels
of pituitary hormones
and events during
menstrual cycle
Fig – 3.1, Page no – 51
Fig – 3.11 Page no – 52
Labelling of mature
graafian follicle
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Page 53
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Page 52
Page 54
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Page 53
Fig – 3.12 Page 53
Page no – 54
Hormones involved
at the time of
parturition
4
Reproductive
Health
Meaning, colostrum and its
importance
1. Reproductive health
(i) Problems & Strategies
2. Methods of birth control
3. Infertility – Corrective treatments
4. Sexually transmitted diseases
2 methods of birth control
(i) natural methods
(ii) barrier methods
(iii) IUDs
(iv)oral contraceptives
(v) injections and implants
(vi)surgical methods
4. Menstrual
(i) Menarche and menopause
(ii) Phases of Menstrual cycle with
diagram
(iii) Role of hormones in cycle
5. Fertilisation & implantation
(i) structure of ouvum
(ii) cleavage – formation of morula,
blastula
(iii) implantation – meaning, stage,
site
(iv) sex determination in humans
(v) three germs layers
6. Pregnancy & embryonic
development
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Page no – 54
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Page 57-58
Page 59-61
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Page 64
Page 63
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49,51
fig 3.9, page 49-51
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Fig 3.1, page 51
Fig 3.11, page 52
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Page 53
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Page 52
*
Page 54
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Page 53
Amniocentesis
Specific site for
transplantation of
embryo in GIFT and
ZIFT
(i) placenta
(ii) embryo & embryonic layers
7. Parturition
(i) Meaning, role of hormones
5
Principles of
inheritance and
variations
8. Lactation
(i) Meaning, colostrum and its
importance
1. Mendel’s laws of inheritance
(i) Reasons for choosing garden pea
(ii) Seven contrasting traits of pea
plant
(iii) Symbols and terms used in
mendel’s experiment
(iv) Steps involved in mendel’s
experiments
(v) Monohybrid cross
(vi) Test cross
(vii) Incomplete dominance
(viii) Codominance and multiple
alleles
(ix) Dihybrid cross
2. Chromosomal theory of
inheritance
3. Linkage and recombination
4. Sex determination in animals
5. Mutations
6. Genetics disorder
(i) Pedigree analysis
(ii) Mendelian disorders
(iii) Chromosomal disorder
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Fig 3.12
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Page 54
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Page 54
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Hormones secreted
by placenta
Page 11/7 of Pradeep’s Textbook
Fig 5.1 page 70—71
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Page 71-73
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Page 70-71
Page 71-75
Fig 5.5 74-75
Fig 5.6 page
Table 5.3 page 77-78
Gamete formation in
dihybrid cross
Fig 5.7 page 79
Table 5.3 fig 5.8-5.9
Page 83-84
Fig 5.12 page 85-86
Page 87
Page 87-88 fig 5.13, 5.14
Page 89-90
Page 90-91
Heterogametey in sex
determination
Use of symbols for
autosomal and sex
linked disorders
6
Molecular basis of
inheritance
1. Dna
(i) structure and salient features
(ii) packaging of dna helix
**
Page no. 96-98
Polarity of two stands
Fig 6.4 page 99
Histone and non
histone chromosomal
protein
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2. Search for genetic material
(i) transforming principle
(ii) hershey and chase experiment
(iii) properties of genetic material
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Page 100-101
Fig 6.5 Page 102
3. Replication – experimental proof
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Page 103
4. Transcription
(i) transcription unit
(ii) type of rna and process of
transcription
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***
Fig 6.7, 6.8 page 105-107
5. Genetic code
(ii)Mutations and Genetic Code
(iii) TRNA-The adapter Molecule
6. Translation
7. Regulation of Gene Expression
(i) Levels of Regulation
(ii) The lac operon
8. Human Genome Project
9. DNA Finger printing
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Fig 6.9, page 107-108
109-111
page 112
Page 113
Fig. 6.12 Page-114
Fig. 6.13 Page 115
Page 115
Fig. 6.14,Page 116,117
Page118-120
Fi. 6.16 Page 121-122
Differentiation
between
transformation and
transaction
Leading and lagging
strand direction
Polycistronic,
monoistronic,
capping, taling
Frame Shift and Point
mutation
Charging of tRNA
Expresses Sequence
Tags Sequence
Annotation
BAC/YAC
Satellite DNA,VNTR
7.
8.
Evolution
Human Health &
Diseases
1. Origin of Life
2. Evidences of Evolution
3. Adaptive Radiation
4. Biological Evolution
5. Mechanism of Evolution
6. Hardy-Weinburg Principle
7. A Brief Account of Evolution
8. Origin and Evolution of Man
1.Common Diseases in human
2. Immunity
(i) Innate immunity
(ii) Aquired immunity
(iii) Active and Passive immunity
(iv) Vaccination and immunity
(v) Allergy
(vi) Autoimmunity
(vii) Immune System of Body
3. AIDS
4.CANCER
5. Drug and alcohol abuse
(i) Adolescence and drugs
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Fig 7.1
Fig. 7.3 Page 130-132
Fig. 7.5,7.6,7.7 Page 133
Page 134
Page 135
Fig. 7.8 Page 136-137
Fig. 7.9,7.10
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Fig. 7.11 Page 140
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Fig. 8.1 Page 146-149
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Page 150-154
NCERT
Fig. 8.4
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Branching Desent
and Natural Selection
Darwinism versus devries- -Saltation
Hardy-Weinburg
Equlibrium,Founder
Effect
Specific Role of
histamines and
cerotonins
Mucosal associated
lymphoid Tissue
CMALT
Fig 8.6 Text 156
Text Page 156-158
Text Page 158-163
Contact Inhibition
9.
10.
Strategies for
Enhancement in
food Production
Microbes in
Human Welfare
1. Animal husbandry
(i) Management of farm and farm
Animal
(ii) Animal Breeding
(iii) Bee Keeping
(iv) Fisheries
2. Plant breeding
(i) Method
(ii) For disease Resistance
(iii) For Pest Resistance
(iv) For Improved food quality
3. Single cell Protein
4. Tissue Culture
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1. Role of Microbes in:(i) House Hold
(ii) Industrial Product
(iii) Sewage Treatment
(iv) Production of Bio Gas
(v) As Biocontrol Agent
(vi) As Biofertlizers
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Page 165-170
Text
Page 170-176
Text Portion
Page176 Text Portion
Page 177 Text Portion
Text Page 181
Page 182,183 Ex. Question 12
Page 184-185 Ex. Question 7,8,11
Page 185
Page 186-187
Page 188
11.
Biotechnology
1. Principles of biotechnology
NCERT text book xii fig . 1.2(a)
Fail to differentiate
principles and
(i) techniques used in modern
(b) fig. 1.3, 1.4 page 5-8
asexual reproductive
processes
biotechnology
*
structures-
(ii) advantages of sexual
zoospores,
reproducton over a sexual
NCERT book p – 15 - 19 ex q
conidium, gemules
reproduction
2,6,9,13,15,18
etc.
(iii) genetic engineering includes
**
reconibinant dna, genecloning a
Differentiation in
gene transfer
monoecious &
(iv) meaning and use of plasmid
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restriction enzymen
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(v) basic steps for gmo
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2. Tools of Recombinant DNA
Technology
3. Cloning Vectors
4. Processes of Recombinant DNA
Technology – Steps
diocious
Fig. 11.1-11.2-11.3
Page-195- 198
Fig. 11.4 Page-198-200
Fig. 11.6,11.7 Page 201-205
12.
Biotechnology and
1. Applications of Biotechnology in
its applications
agriculture
(i) Advantages of GMO
(ii)Bt Cotton
*
Differentiation of
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(iii) RNA interference
2. Applications of Biotechnology in
Medicines
(iii) Molecular Diagnosis of
Page 208
Cry and cry
Page 208-209
nRNA silencing ,
Page 209-210
nematode –
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(i) Genetically engineered insulin.
(ii) Gene Therapy-ADA
Page 207-208
Meloidegyne
Page-210-211
incognitia
Page 211
Steps in production
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of insulin
Page-212
diseases.
3. Transgenic animals
4. Ethical issues , Biopiracy
Role of
Biotechnology in
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Page-213
Page-214
molecular diagnosis.
13.
Organisms and
1. Organisms and its Environment
Populations
(i) Major Abiotic Factors
Eurythermal &
stenothermal
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(ii) Responses to Abiotic Factors
Page -221-223 NCERT
Conformers,
Fig. 13.3 Page 223-225
Regulators
Page 225-226
Distinction between
Fig. 13.4 Page 226-228
Expanding, stable,
Fig. 13.5 Page 228-231
declining population.
Page 231-232
Distinction between
Table 13.1 Page 232-238
Exponential and
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(iii) Adaptations
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2. Populations:***
(i)
Population Attributes
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(ii)
Population Growth
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(iii)
Life History variation
(iv)
Population interactions
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Logistic growth
curve.
Distinction between
commensalisms and
Amaensalism.
14.
Ecosystem
1. Structure and function
Page 242
2. Productivity
Ex Q. 9
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3. Decomposition
Fig. 14.1 Page 243-244 Ex. Q10
GPP,NPP
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4. Energy Flow
Page 245,247 Ex. Q. 11
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5. Ecological Pyramids
Fig. 14.4 Page 248
6. Ecological succession
Fig. 14.5 Page 250-251
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7. Nutrient cycling
Fig. 14.6 Page 253-255 Ex. Q.
12,13
15.
Biodiversity and
Conservation
1. Patterns of Biodiversity
2. Importance of species
diversity to ecosystem.
3. Loss of Biodiversity
4. Conservation of
Biodiversity
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Fig. 15.1 Text page 259 Ex. Q 3
Page 263
Page 264-265 Ex. Q. 5
Page 265-267 Ex. Q. 7
Graphical
representation ,
species area
relationships
Crypreservation
16.
Environmental
issues
1. Air Pollution and its control
(i)
Case study of Delhi
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Fig. 16.1 Page 270-273
Advantages of CNG
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Page 272-273
over Petrol or diesel.
2. Water pollution and its control
(i)
Domestic Sewage &
Norms of Air
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Page-274 Fig.16.2,16.3
Industrial effluents
Pollution.
Types of impurities
(ii)
Algal Bloom
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Page 275
& their nature in
(iii)
BOD
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Page- 275
domestic sewage.
(iv)
Eutrophication
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Page-276
Effect of Sewage
(v)
Biomagnification
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Fig. 16.5 Page-276
discharge on
3. Solid waste
(i)
characteristies of
Case study of remedy
river
for plastic waste.
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Page-279
Electronic waste
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Page-279
Concentraion of toxic
4. Ago chemicals & their effects
*
Page-279
substances at various
(i) Case study of organic farming
**
Page-280
trophic levels
(ii)
5. Radioactive wastes
Page-280
6.Greenhouse effect and Global
Page-280-282 Fig. 16.6,16.7
Warming
Types of e-wastes &
(i) Green house gases & their
the metals extracted.
relative contribution to total global
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warming
7. Ozone depletion in Stratosphere
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Page-282-283
Role of UV-B
8. Deforestation:- Case study of
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Page-284-285
radiations
conservation.
Contents
S No Chapter
Pages
1
Reproduction in animal
0-11
2
Sexual reproduction in flowering plants
12-17
3
Human reproduction
18-36
4
Reproductive health
37-46
5
Principles of inheritance and variation
47-63
6
Molecular basis of inheritance
64-96
7
Evolution
97-105
8
Human health and diseases
106-124
9
Strategies for enhancement in food production
125-130
10
Microbes in human welfare
131-142
11
Biotechnology :principles and processes
143-167
12
Biotechnology and its application
168-172
13
Organisms and populations
173-183
14
Ecosystem
184-192
15
Biodiversity and conservation
193-195
16
Environmental issues
196-208
17
Wordlist Concept Mapping
208-209
18
Word List
210-214
19
Hots Assignments
215-246
20
Assignments of different difficulty levels
21
Assignments for self evaluation
CONTENTS
Sl No
Chapter
Pages
1
Reproduction in animal
0-11
2
Sexual reproduction in flowering plants
12-17
3
Human reproduction
18-36
4
Reproductive health
37-46
5
Principles of inheritance and variation
47-63
6
Molecular basis of inheritance
64-96
7
Evolution
97-105
8
Human health and diseases
106-124
9
Strategies for enhancement in food production
125-130
10
Microbes in human welfare
131-142
11
Biotechnology:principles and processes
143-167
12
Biotechnology and its application
168-172
13
Organisms and populations
173-183
14
Ecosystem
184-192
15
Biodiversity and conservation
193-195
16
Environmental issues
196-208
17
Wordlist Concept Mapping
208-209
18
Word List
210-214
19
Hots Assignments
215-246
Chapter – 1: - REPRODUCTION IN ORGANISMS
 REPRODUCTION IN ORGANISMS
 Life Span
 Period from birth till natural death.
Every organism live only for a certain period of time.
Example: Elephant: 60-90 years
Fruit fly: 4-5 weeks
Reproduction –Producing young-ones of their kind, generation after generation.
Types of reproduction:
Asexual reproduction :single parent capable of producing offsring.
 Sexual reproduction : two parents are invovled in producing offspring.
Modes of asexual reproduction
 Binary fission: parent body divides into two halves, genetically identical to parent.
Amoeba: It is simple or irregular.
Paramoecium: Transverse binary fission.
 Multiple fission: parent body divides into many daughter organisms : Plasmodium.
 Budding: daughter organisms grow from small buds arising in parent body.
Exogenous budding: out side the body eg. Hydra, Yeast.
2
4
Budding in Yeast
Endogenous budding : inside the body eg. Gemmule in sponge.
 Conidia: non-motile, exogenous spores in chains eg. Fungi.
 Zoospores: microscopic motile structures eg. Algae.
In plants : term vegetative reproduction frequently used instead of asexual reproduction, units
of vegetative propagation called vegetative propagules.
Adventitious buds in
Bryophyllum
Sexual reproduction

All organisms show remarkable similarity Vast difference in their reproductive structure. Similar
pattern or phases in their life cycles.
 Juvenile phase: The phase of growth before reproductive maturity.
 Reproductive phase: Reproductive maturity.
 Senescent phase: Phase between reproductive maturity and death.
The main events of sexual cycle are:



i. Prefertilisation events:
a.Gametogenesis :
The process of formation of male and female gametes by meiosis(cell-division).
2
5
Homogamete(Isogamete): - gametes similar eg. Algae
Heterogamete(an-isogamete): - morphologically dissimilar gamete ,male gamete (antherzoid or sperm)
,female gamete (egg or ovum) eg. Human.
Sexuality in organisms : In plants
Bisexual term is used for Homothallic and Monoecious plants

Both male and female reproductive structures in same plant eg. Higher plants, cucurbits
and coconut.
Unisexual term is used for Heterothallic and Dioecious plants
Male and female reproductive-structure on different plants.,
Flowering plants – male flower–staminate flower and female flower–pistillate flower
eg. papaya and date-palm.
Animals – Bisexual term is used for Hermaphrodite animals-eg. Earth-worm, Tapeworm, Leech, Sponge.
Unisexual animals have male & female sexes in separate individuals-e.g. insects,
frogs, humanbeings
Cell division during gamete formation:
Hapliod-parent (n) produces haploid gametes (n) by mitotic division, eg. Monera,fungi,
algae and bryophytes.
Dipliod parent (2n) produces haploid gametes(n) by meiosis division (possess only one
set of chromosomes)and such specialized parent cell is called meiocyte or gamete
mother cell. ExampleName of organism
in Meiocyte(2n)
gamete (n)
Human
46
23
Housefly
12
6
1260
630
Ophioglossum (fern)
2
6
Potato
48
24

b) Gamete transfer:- to facilitate fusion.

Male gametes mostly motile and female non-motile,exception few fungi and in algae both
gametes are motile in some cases

Water medium for gamete transfer- in lower plants. Large number of male gametes produced to
compensate loss

Higher plants, pollen-grains are transferred by pollination.

Fertilization: Fusion of male and female gametes diploid zygote.

Parthenogenesis.-development into new organism without fertilisation eg. Rotifers, honey-bees,
some lizard, bird(turkey).
Fertilization
Two types- external and internal .

External fertilisation- outside the body of organism in external- medium (water) eg.
majority of algae, fishes, amphibians.
Advantageshow great synchrony between the sexes –
1.release of large number of gametes into surrounding medium
2.large number of offsprings produced.
Disadvantage- offsprings are extremely vulnerable to predators, natural disasters.

Internal fertilisation- fusion occurs inside female body eg. majority of plants and animals.
Egg non-motile and formed inside female body. Male gamete motile, produced in large
numbers to reach egg and fuse with it. In seed plants, non- motile male gamete carried to
female gamete by pollen-tube.
Post -fertilisation events- formation of zygote.
a. zygote. One celled , diploid, vital link between two generations.

External fertilization –zygote formed in external medium water eg. Frog,

Internal fertilization –zygote formed inside the body eg. Humanbeings.
Development of zygote depends on type of life cycle and environment. Some develo thick wall (
prevent damage and desiccation) & undergo period of rest eg. algae, fungi. In haplontic life cyclezygote (2n) divides by meiosis to form haploid (n)spores.

Diplontic life-cycle- zygote (2n) divides mitotically, develops into embryo(2n).

Oviparous animals lay eggs out-side the female body.Eggs can be fertilized/ unfertilized.
Fertilized eggs covered which hard calcareous shell, laid in safe place in the enviroment.
Unfertilised eggs laid in water. Example- fishes, frogs, reptiles, birds
2
7

Viviparous animals bear and rear the embryo inside female body, give birth to youngones.Advantage- proper embryonic care, protection, survival chances of young-ones greater.
Example- cows, whales, humanbeings

Embryogenesis: development of embryo from zygote by cell division (mitosis) and cell
differentiation. Cell- division increases the number of cells in the developing embryo
Cell differentiation - groups of cells undergo certain modifications for the
different kinds of tissues and organs.

In flowering plants- zygote formed inside ovule Changes occur in flowering plants:
sepals, petals, stamen- wither and fall-off. Zygote develops into embryo. Ovule forms the seed
(germinates to produce new plants).
Ovary transformed into fruit which develops protective thick wall-pericarp.

Parthenogenesis: Female gamete develops into new organism.

Seedless fruits can be formed by parthenogenesis

Clone: A group of individuals of the same species that are morphologically and genetically
similar to each other & their parents
Very short answer type(1 mark)

What is meiocyte?
Specialized cells in diploid organism, i.e., gamete mother cell which undergo meiosis.

Name the kind of reproduction in bees by which drones are produced?
Parthenogenesis.

formation of
What is special in flowering bamboo?
Bamboo species flower only once in their life-times generally after 50-100 years.
2
8

What is meant by homothallic?
The term homothallic refers to bisexual or hermaphrodite condition.

Why are the date palms referred to as dioecious ?
In date-palms, the male and female flowers are present in different plants.

If the diploid number of chromosomes in an angiosperm plant is 28, what number would you
expect in the endosperm and embryo of that plant?
Endosperm: 48
Embryo: 28

Give the scientific terms for the following
a. Morphologically and genetically similar individual derived through asexual reproduction.
b. Cyclical changes shown by seasonal breeders.
a. Clone
b. Oetrous cycle
Short answer type (2 marks)

Name the structure which gets transformed into seeds at maturity.
ovule

Name any one animal in which self-fertilization occurs.
Taenia (tapeworm)

What is the site of origin of new plantlets in the followings ?
a. Potato tuber,
b. rhizome of ginger,
c. leaves of bryophyllum,
d. stem cutting of sugar cane
a.Buds called eyes
b.Adventitious buds at Nodes
c.Advevtitious buds from the notches at margins of leaves
d.A portion of stem with buds at nodes
7

What do the fallowing parts in a flower form after fertilization?
a. Zygote,
b. ovule,
c. ovary-wall,
d. Petal
a.Embryo
b.Seed
c.Pericarp
d.Wither and fall off
Draw a diagram of the cross section of a simple fruit and label two important parts-
Show diagrammatically only reproduction in yeast.
8
Short type answer (3 marks)
Q
Write the mode of asexual reproduction in the following organisms:
Penicillium, Spongilla, Paramoecium, Yeast, Chlamydomonas, Amoeba.
Ans:-
Penicillium: Conida.
Spongilla: Internal budding (gemmules).
Paramoecium: Binary fission (transverse).
Yeast: Budding (external).
Amoeba: Binary fission (simple).
Chlamydomonas: Zoospore.
Q
Differentiate between: External Fertilization / Internal fertilization, Zoospore / zygote,
Gametogenesis / Embryogenesis.
External fertilization
1.
2.
Internal fertilization
Occurs outside the body of females.
Inside the body female
Large number of gametes are released
into the surrounding medium.
Number of gametes produced is less.
Ex- fishes, frogs
Gametogenesis
Haploid gametes formed
Two types: spermatogenesis (formation of male
gamete) and oogenesis (formation of female
gamete
Meiosis occurs.
Ex- lizard, humans
Embryogenesis
Multicelluar embryo from cd unicellur from
zygote
Involves cell division, cell growth, celldifferentiation
Mitosis occur
Zoospores
Zygote
9
Formed inside zoosporangium
Fusion of two gametes
Flagellated and motile
Usually nonflagetted and non motile or motile
Result of asexual reproduction
Result of sexual reproduction
Haploid or dipliod
Dipliod
Q. What are the three major phases in the life cycle of organism? Define each phase
Ans. The three major phases are:

i. Juvenile phase.

ii. Reproductive phase.

iii. Senescent phase.

Juvenile phase: The Phase of growth before reproductive maturity.

Reproductive phase: Attainment of reproductive maturity. Some major hormonal changes mark
this phase.

Senescent phase: The phase between reproductive maturity and death.
Q. What is external fertilization?

Name two animals having external fertilization.

Why are more gametes produced by such animals?

Fertilization occurs outside the body of organism

Frog and bony-fish

Large no of gametes to enhance produced the chances of fertilization
Long answer type question(5 marks)

Discuss the similarities in pattern of sexual reproduction.
A) Pre-fertilization: Prior to the fusion of gametes after attainment of maturity. This includes two
main events:
i. Gametogenesis: Formation of two types of gametes – male and female which involves
spermatogenesis in males and oogenesis in females.
ii. Gamete transfer: It is to facilitate fusion. Medium by water, pollination, copulation.
B) Fertilization: Fusion or syngamy.
10
C) Post-fertilization: Single celled zygote.
Embryogenesis: Process of Development of embryo from zygote. Zygote undergoescell-division and cell-differentiation. By cell-division- it increases the number of cell
cell-differentiation- group of cells undergo certain modifications to form specialized tissues and organs to
form an organism.
HOTS:
FIVE MARKS QUESTIONS:
1. Study the following diagram and answer the questions given below:
i. What does S and P denote?
ii. Where do they develop from?
iii. What is the term given to the point of attachment of the ovules in the fruit?
iv. What is the ploidy of embryo and the tissues in the ovary?
v. What is the function of fruit apart from storage of materials?
2. Fertilization leads to the formation of embryo.
i. Give the technical term for the development of embryo.
ii. What are the events that occur during embryo development?
iii. The development of zygote depends on two factors. What are they?
iv. How will you categorise animals based on the development of zygote inside or
outside the female body?
v. How does zygote in fungi and algae overcome dessication?
Chapter – 2 SEXUAL REPRODUCTION IN FLOWERING PLANTS
FLOWERS
Site of sexual reproduction.
Male & fema le reproductive organs are borne on flower s.
11
a PARTS OF A FOWER: 4 WHORLS - CALYX (sepals), COROLLA(petals), ANDROECIUM(
Male reproductive organ), GYNOECIUM( Female reproductive organ).
Male reproductive organ
Androecium consists of stamens
Stamen consists of anther , filament & connective( when anther is bilobed)
Anther is bilobed & has 4 microsporangia
L.S. OF A FLOWER WITH DIFFERENT PARTS
MICROSPOROGENESIS:
Microspore mother cell (2n)
Meiosis
Microspore (n)
12
Mitosis
Pollen grains (n)
Pollen grains have two outer walls; i) Exine ii) Intine
Exine is made of sporopollenin (HARDEST NATURAL SUBSTANCE)
Mature pollen grains have two cells – big vegetative cell & small generative cell.
Generative cell forms two male gametes by mitotic division.
Pollen grains shed in 2-celled/3celled stage
GYNOECIUM / CARPEL (THE FEMALE REPRODUUCTIVE ORGAN)
-Each Carpel consists of ovary, style & stigma.
- Ovules are attached to ovary by placenta.
-
. Structure of an
Anatrpous ovule
Parts of gynoecium
13
The funicle – stalk of ovule
Hilum, a region where funicle is
attached
Integuments –cover embryo sac.
Micropyle – a pore for entry of pollen
tube & to imbibe water
Structure of anatropous ovule
MEGASPOROGENESIS
Megaspore mother cell (2n)
Meiosis
4 Megaspores (n)
(3 megaspores degenerate,
1 remains functional)
Funtional Megaspore (n)
(Divides 3 times by mitosis)
8 Nucleated Embryo Sac formed
DEVELOPMENT OF 8 NUCLEATED EMBRYO SAC
14
3 cells group at micropylar end -the egg cell(n) & 2 synergids(n)
-
3 cells at chalazal end called antipodals(n)
2 polar nuclei at center(n each )
POLLINATION – transfer of pollen from anther to stigma.
Agents of pollination – air, water, insects.bat,bird,man.
Double fertilization
-
syngamy – 1st male gamete fertilizes egg.
nd
2 male gamete fertilizers fusion product of polar nuclei.
Pollen grains germinate on stigma & pollen tube grows through style.
Pollen tube reaches micropyle & releases two male gametes into embryo-sac.
-
Fertilisation is the process of fusion of male& female gametes (n+n) to form a diploid(2n)
zygote
-
SYNGAMY: Fusion of one male gamete(n) with egg (n)
fusion
Fusion of two polar nuclei(n+n=2n) Second fusion
-
The other male gamete(n) fuses with the fusion product of two polar nuclei(2n)
fusion
-
DOUBLE FERTILISATION: i ) Fusion of male gamete with egg – First fertilization, ii
)Fusion of fusion product of polar nuclei with male gamete – Second fertilisation
POST FERTILISATION CHANGES:
15
Zygote(2n) produced
First
Third
Stages of development of the embryo after fertilation :
STAGES OF EMBRYO DEVELOPMENT AFTER FERTILISATION
1. Zygote divides by mitosis into suspensor & embryo cells
2. Suspensor cell forms a globular basal cell which remains embedded in the endosperm &
a multicellular suspensor bearing the embryo
3. Globular embryo becomes heart-shaped & then mature embryo with radicle, plumule &
cotyledons
Primary endosperm nucleus – divides repeatedly to form endosperm, food for the embryo.
Mature ovary becomes fruit.
Mature ovule beomes seed.
True Fruit develops only from the ovary, e.g. mango, tomato
False Fruit develops from parts of the flower other than the ovary,e.g. apple, pe
Seeds are of two types:
16
Dicot seed
Monocot seed
OUTBREEDING DEVICES:
Continued self-pollination result in breeding depression. Flowering plants have developed many
devices to discourage self-pollination & encourage cross-pollination such as
Bearing unisexual flowers
Anthers & stigmas mature at different times
Anthers & stigmas are placed at different positions
Self-incompatibility where pollen grains of a flower donot germinate on the stigma of the
same flower
ARTIFICIAL HYBRIDISATION:
Type of cross-pollination performed by man for crop improvement.
Achieved by- i ) Emasculation i.e.removal of anthers from the flower bud of a bisexual flower before
the anther dehisces using a pair of forceps and
ii )Bagging i.e.covering the emasculated flowers with a bag of suitable size to protect them from
contamination with unwanted pollen
If flower unisexual, emasculation is not needed. Flower bud bagged & when the stigma becomes
receptive, pollination is done using desired pollen & the flower is rebagged
Emasculation
17
Chapter 3: Human Reproduction
The Male reproductive system
1. Penis
a. urination
b. sexual intercourse
1. Corpus cavernosum- spongy tissue that fills with blood to make penis erect
2. Glans- the head, end of penis
3. Foreskin
i. Covers glans,
ii. May be removed surgically in an operation (circumcision)
a. Located behind penis
b. Contains two testes
c. Temperature sensitive (Sperm must be made in cooler conditions i.e, 2-3 C lower
than body temperature)
2. Scrotum
3. Testes
a. Sperm is produced by the seminiferous tubules due to FSH
b. Testosterone is produced by Leydig cells due to LH
1. Causes the development of the male sex organs at ~8 weeks after conception.
2. Responsible for facial, armpit, and pubic hair, bone growth and muscular
development.
c. Testes are formed in the abdomen before birth. Descend through the "inguinal canal"
during fetal or post-natal life. Sometimes may take months/years to reach right place.
Possible site for hernia.
4. Epididymis:
Stores sperm til mature
5. Vas deferens:
Tube from the epididymis to urethra
sperm cells stored here.
6. Prostate gland:
Provides an alkaline fluid that can protect sperm from harsh vaginal acids.
7. Seminal Vesicles:
Produce food purpose for sperm.
8. Cowper's gland:
Produces clear lubricating fluid
Hormonal control of male reproductive system
1. Pituitary gland at the base of the brain produces:
a.
FSH (follicle stimulating hormone)
1.
b.
FSH regulates spermatogenesis.
LH (luteinizing hormone)
1.
LH prompts Leydig cells to produce testosterone, (male hormone.)
18
Hormonal control of female reproductive system
1. Pituitary gland (at the base of the brain produces):
a.
b.
c.
FSH (follicle stimulating hormone)
i.
Responsible for maturation of follicles and respective ova.
ii.
Stimulates estrogen production.
LH (luteinizing hormone)
i.
Ovulation- release of ovum from ovary usually on 14th day of menstrual
cycle. Ovulation generally occurs every 28 days.
ii.
Causes the corpus luteum to produces progesterone and estrogen.
Progesterone hormone of pregnancy.
Estrogen: the main female hormone produced in Graffian follicles of ovary -
1. increases size ( growth and development) of oviducts, uterus, and
vagina.
2. responsible for secondary sexual characteristics:
3. Fat in breasts and development of duct system.
4. Broadening of the pelvis.
5. Soft and smooth skin.
6. Fat in buttocks and thighs.
7. Pubic hair..
d. Oxytocin – causes uterine contraction during Parturition.
e. Progesterone produced by corpus luteum. (ruptured graffian follicle after ovulation) The
placenta continues to produce progesterone during the pregnancy.
1.
2.
3.
pregnancy hormone
calms muscular contractions of the uterus.
It (along with estrogen) thickens the lining of the uterus.
f. Hormones from Placenta:
hCG: human chorionic gonadotrophin
hPL : human placental lactogen
Female Reproductive System.
2. Ovaries produce:
a.
Ova:
I)
ii)
each ovary contains immature ova (eggs) in follicles.
Females are born with lifetime supply of eggs. (250,000-400,000 in each
ovary) –
19
iii)
Ovaries release ovum -. Almost all ova degenerate between birth and
puberty.
iv)
Approx. 400 eggs will be ovulated over woman's life.
v)
An egg is the largest human cell.
vi)
Ovaries are located lower abdomen. One on either side.
vii)
Egg is viable for only 24-48 hours after ovulation.
2. Fallopian tubes
a.
b.
c.
d.
e.
Two thin tubes attached to the upper sides of uterus
Tubes terminate near the ovaries but not attached
"Fimbriae" finger-like structures on the end of each tube
Tubes conduct egg to uterus by use of small hairs called "cilia"
Fertilization of ovum takes place in the ampullary-isthmic junction of the fallopian
tubes.
a.
b.
Pear-shaped located in lower abdomen
Muscles (myometrium) stretch to allow baby to develop. Oxytocin starts labor
contractions.
Lining of uterus (endometrium) thickens with blood-rich tissue due to progesterone
Endometrium supports embryo/fetus during growth
Placenta (the after birth) attaches to endometrium. Interface between baby and
mother.
If not pregnant, lining breaks down and is discharged from body through vagina. This is
menstruation (period)
Cervix connects uterus to vagina. Like a door that opens during ovulation. Cervical
mucous closes the door at all other times.
3. Uterus
c.
d.
e.
f.
g.
4. Vagina
a. Birth canal
b. Menstrual blood leaves the body
c. Organ of intercourse
d. Very muscular stretches to allow a baby to grow ?
e. Vaginal opening remains partly closed by thin membrane of tissue called hymenf. Hymen may be stretched or torn during any physical activity
6. Cervix
a.
b.
c.
d.
e.
Located at inner end of vagina
Opening of uterus into vagina
Mucous prevents bacteria and viruses from entering uterus
Lets sperm into uterus after ovulation
Baby passes through during vaginal birth
7. Labia
a. 2 layers of skin, which fold over the opening to vagina and urethra
i. Inner labia (labia minora)
ii. Outer labia (labia majora) – site of pubic hair growth
20
8. Clitoris
a. Small organ, 5 to 10 millimeters long
b. Located at junction of inner labia near front of body
c. Contains erectile tissue
d. Sexually sensitive
9. Mons pubis
Cushion like fatty tissue covered by skin and pubic hair
Difference between
1) Spermatogenesis and oogenesis
Spermatogenesis
Oogenesis
Produces male gametes (sperm)
Produces female gametes (oocytes)
–occurs in the seminiferous tubules (in testes)
–occurs in the ovaries
–involves meiosis
– involves meiosis
–occurs throughout life after puberty
occurs after puberty until menopause
may produce 400,000,000 per day
–humans normally produce one oocyte during
each ovarian cycle
Primary spermatocyte divide equally to form
two similar secondary spermatocytes
Primary otocyte divide unequally to form one
large secondary oocyte and a small polar body
One spermatogonium produces 4 functional
spermatozoa
An oogonium produces one functional ovum
and 3 non functional polar bodies
Role of amniotic fluid
1 Prevents desiccation
2 Shock absorber
21
Menstrual Cycle
Menstruation
Repair of the
endometrium
Follicular Phase
Ovulation
Thickening of the
endometrium
Due to LH
FSH/Estrogen
Breaking
down
Luteal Phase
LH/Progesterone
2)Follicular phase (Proliferative phase ) and Luteal phase (secretory Phase)
Proliferative phase
Secretory Phase
Also called Follicular phase
Also called Luteal phase
Stage of repair and proliferation
Prepares endometrium for implantation
It extends from the end of menstruation to
ovulation
extends after ovulation to menstruation
LH and FSH increases
LH is high (LH surge)
Estrogrn level inceases
Progesterone level increases
Estrogen is secreted by Graffian follicle
Progesterone secreted by corpus luteum
22
The menstrual can be represented as
23
Notes on FSH and LH
FUNCTION
/ PRODUCTION
FSH and LH from the pituitary:
Hormone
In Females
In Males
FSH Controls 
Eggs + Estrogen
Spermatogenesis
LH Controls 
Ovulation +
Corpus Luteum
Testosterone
.The follicle stages
24
From primordial follicle to tertiary follicle
Primordial follicle
the surviving primary oocytes , at birth, are surrounded by thin, single layers cells of so-called follicular
epithelial cells.
Primary follicle
Primordial follicles with iso or prismatic follicuilar follicles the follicular epithelium surrounding the
oocyte becomes iso- to highly prismatic
A
B
1
2
Primordial follicle
Primary follicle
Oocyte
Follicular epithelium
1
2
3
4
Oocyte
Pellucid zone
Stratum granulosum
Theca folliculi cells
Secondary follicle
Follicles with multiple rows of follicular epithelium stratum granulosum.
Pellucid zone:- Zone between the oocyte and follicular epithelium.
Tertiary follicle
Follcile with well-developed net of capillaries in the theca interna.
Antrum – a fluid filled cavity.
Theca layers of cells organized into external Theca externa and interna linterna.
Tertiary follicle
25
1
2
3
4
5
6
7
8
Oocyte Pellucid zone
Stratum granulosum
Theca interna
Theca externa
Antral follicle
Cumulus oophorus (Granulosa cells, together with the oocyte)
Basal lamina between theca and stratum granulosum
Schematic stage
From fertilization to embryo
Sperm
+
secondary oocyte
Fertilized ovum (zygote)
2-cell stage
4-cell stage
8-cell stage
Morula
Blastula
Early Gastrula
Late Gastrula
Cleavage-
cells division of embryo similar to mitotic division
26
Morphogenesis-
stage distinct shapes start to appear
Differentiation-
formation of distinct cells and tissues
Growth-
cells get bigger and so does embryo
Conception to Birth
The following shows some of the many stages of human development:
Zygote
=
Morula
=
The single cell that results from
fertilization of an ovum by a sperm.
*The morula (little mulberry)I
Blastocyst
solid ball (16 64 cells.
Morula results of mitotic
(cleavage)divisions.
=
The blastocyst is a liquid-filled ball of
cells. This stage of development occurs
around 5 – 8 days after conception.
Implantation in the endometrium
occurs at this stage.
27
Embryo
=
The human is considered an embryo
from implantation until about 8 weeks
after conception.
Fetus =
8 weeks after conception until birth.
The fate of three germ layer
28
Ectoderm
Mesoderm
Endoderm
Nervous system
Skeleton
Digestive tract
Epidermis of skin
Muscles
Respiratory system
Circulatory system
Liver, pancreas
Gonads
Bladder
Mnemonics
Tubules in male reproductive system
29
―SEVEN UP‖
Seminiferous tubules
Epididymis Vas
deferens
Ejaculatory duct
(Nothing)
Urethra
Penis
Menstrual Cycle
―FOL(d) M(a)PS‖
Ovarian cycle:
Follicular phase
Ovulatory phase,
Luteal phase
D Menstrual cycle:
Menstrual flow,
A Proliferative phase,
Secretory phase
(The ovarian cycle controls the menstrual cycle. The cycles begin (day 0) when menstrual flow
starts. At day 14, ovulation take place. The luteal and secretory phases begin and last until day
28,after which the cycles begin again.)
TERMS TO REMEMBER
Acrosome- the part of a sperm cell that contains enzymes – (This enables a sperm cell to
penetrate an egg.)
Afterbirth-placenta and fetal membrane expelled from the uterus after the birth of a baby
Amniotic sac-fluid-filled membrane or sac that surrounds the developing embryo while in the
uterus; ". (Protects the baby from hard shocks and keeps it at a constant temperature. )
Birth-the process of being born; the baby moves from the uterus into the outside world.
Parturition
Blastocyst = blastula = early stage of an embryo surrounded by a liquid-filled sphere whose wall
is composed of a single layer of cells A+ this stage (about eight days after fertilization)
implantation in the wall of the uterus occurs.
Cervix- the lower part, or neck, of the uterus. (Opening to the uterus.)
30
Clitoris-small, sensitive organ in front of the vagina
Coitus-synonym for sexual intercourse
Conception-fertilization of an egg cell by a sperm cell
Corpus Luteum - Crater-like structure formed after ovulation produces progesterone and
estrogen. Old RUPTURED GRAFFIAN follicle. It means ―yellow body‖ .
Cowper's glands - 2 glands that secrete an oily liquid, which cleans and lubricates the urethra
of the male
Egg cell-a female sex cell (female gamete or ovum or secondary oocyte )
Ejaculation-the discharge of semen from the penis
Embryo-the unborn child developing in the uterus between the second and eighth weeks of life
Endometrium - the innermost lining for the uterus, Site for blastocyst to implants and develop.
Epididymis- tightly coiled tube at the back of each testis holds newly produced sperm – (each
epididymis is like a nursery where sperm mature and learn to swim.)
Erection-the condition of the penis when it fills with blood and becomes firm, enlarged, and
erect.
Fallopian tube -tube one from each ovary leading to the uterus. Carry the egg from the ovary to
the uterus. Fertilization occurs here. (Also known as the oviducts.)
Fimbria - (plural fimbriae) means "fringe." a fringe of tissue near the ovary leading to the
fallopian tube
Fertile- able to conceive a child
Fertilization-Union of a sperm and an egg. Conception.
Fertilized egg- Egg after a sperm has united with it. Zygote
Fetus- Unborn child developing in the uterus after the first eight weeks of life
Follicle - Found in ovaries. Each holds and nourishes the egg until ovulation. It is like a nest.
Will become corpus luteum after ovulation.
Foreskin – A sheath of skin that surrounds the penis.
Follicle Stimulating Hormone - hormone secreted from pituitary gland in both men and
women. In women, FSH promotes the development of eggs and estrogen. In men, FSH promotes
the development of sperm cells.
Fraternal twins-babies that develop from two eggs, each fertilized by a sperm cell; may or may
not be of the same sex
Gamete – Sex cells. Sperm cells and egg cells are gametes.
Genitals-Reproductive or sex organ. especially the external organs
Germ Cell- An egg or sperm cell. A gamete. In humans, a germ cell contains 23 chromosomes
Hormones-chemical substances produced by the endocrine glands Act in other parts of the body
and affect maturation, growth, and behavior; LH, FSH, GH, Testosterone, Estrogen,
Progesterone are all hormones.
Hymen-a thin tissue or membrane that may partially cover the opening of the vagina
Identical twins-babies that develop from a single fertilized egg that separates into two halves.
Identical twins always of the same sex
Labia-two folds of skin surrounding the entrance of the vagina
Labor-the muscular contractions that expel a baby from the uterus during childbirth
Leydig Cells – when prompted by LH, Leydig cells create testosterone.
LH - Luteinizing Hormone - Secreted from the pituitary gland and causes ovulation and the
formation of the corpus Luteum in women. In men, LH causes the Leydig cells to produce
testosterone.
31
Menstrual cycle -The periodic building up and sloughing off of the lining of the uterus
approximately every twenty-eight days
Menstruation- The periodic discharge of blood and waste material (unfertilized secondary
oocyte / ova and the degenerating endometrium lining) from the uterus
Miscarriage-expulsion from the uterus of a fetus before it is developed sufficiently to live
Spontaneous abortion
Myometrium – muscles of the uterus that stretch to accommodate the growth of the baby.
These muscles contract during labor and push baby out…
Orgasm-the peak of sexual excitement when the male ejaculates semen. Ovaryfemale sex glands. Produces egg cells, estrogen and progesterone. OvulationDischarge or release, of an egg cell / secondary oocyte from the ovary Ovumscientific name for an egg cell / secondary oocyte
Oxytocin - Hormone, released from the pituitary gland , stimulates contraction of the
myometrium of the uterus during labor and facilitates ejection of milk from the breast during
nursing.
Penis-the male sex organ through which sperm cells leave the body. Also discharges urine
Placenta- network of blood vessels and other tissues by which the unborn child is attached to
the wall of the uterus. Grows out of the endometrium The umbilical cord is attached to it. It is
the interface between mother and developing fetus.
Pregnancy-the process in a woman from conception to birth
Pregnant-the condition of a woman with an embryo or fetus in her uterus
Progesterone – pregnancy hormone. First produced by the corpus luteum and then by the
placenta.
*Progesterone increases lining of endometrium.
*maintains pregnancy
* helps in development of mammary glands.
Prostate gland- Organ that surrounds the upper end of the male urethra and produces part of the
fluid that mixes with the sperm to form semen. Prostate fluid is alkaline and helps to protect
sperm from vaginal acids.
Scrotum-Pouch of loose skin containing the testes. This houses and air-conditions the testicles
by moving and sweating.
Semen-Mixture of sperm and fluids that appears at ejaculation. Semen is comprised of sperm,
fructose, prostate fluid and oil from the Cowper‘s gland.
Seminal vesicles-small saclike organs opening into each vas deferens near the upper end of the
urethra. Produce part of the fluid that mixes with the sperm to form semen. Provide food
(fructose) for the sperm.
Seminiferous tubules - Tubes found in the testes that produce sperm
Sexual intercourse- The entry of the penis into the vagina and the subsequent release of semen
coitus
Sperm- The male sex cell (male gamete or spermatozoon), which contains 23 chromosomes in
humans.
Spermatozoon- Scientific name for sperm
Spontaneous abortion-- Synonym for miscarriage
Testes- Male sex glands. Produce sperm cells and testosterone.
Testicles-synonym for testes
Testosterone – Male hormone that regulates the development of the penis, muscles, body hair,
etc…
32
Umbilical cord-the ropelike structure connecting the embryo or fetus to the placenta within the
uterus.
Urethra-the tube through which urine is expelled from the bladder in both males and females
and through which semen leaves the male body
Uterus = womb - the hollow pear-shaped organ in which a baby develops before it is born;
Vagina-the passage from the uterus to the outside of the body.
- accepts the penis during intercourse.
-Birth canal.
-Menstrual fluids leave through it
Vas deferens-The tube extending from each epididymis to the urethra in males
Womb- Synonym for uterus
Yolk sac- Structure that develops for the nutrition of the embryo during early embryonic life
and then ceases to function
Zygote - Cell formed by the union of two gametes, [ fertilized ovum before cleavage.]
*********************************
Practice material
Chapter 3
HUMAN REPRODUCTION
1 mark questions
1.
2.
3.
4.
5.
6.
7.
Where does fertilization takes place in human female?
Where and at what stage implantation takes place?
What harm is caused if the testis fail to descend into the scrotal sac?
Name the layer of cells forming the outer layer of blastula?
What is semen?
Why progesterone is called pregnancy hormone
Name the hormones secreted by
a.
leydigs cell
b.
graffian follicles
c.
Corpus luteum
d.
Placenta
2 marks questions
8. Differentiate between
a.
Spermiogenesis and spermatogenesis
b.
Follicular phase (proliferative phase) and Luteal phase (secretory phase)
c.
menarch and menopause
d.
Spermatogenesis and oogenesis
e.
morulla and blastulla
9.
10.
11.
12.
How is ovulation different from menstruation?
How does the ovum ensure that only one sperm fertilizes it?
Name the accessory reproductive glands in human male along with its secretion and functions
What is colostrum? What is its significance?
33
―Placenta acts as an endocrine gland‖ why it is said so ? What are its other function?
Where does oogenesis occurs in human?. Describe the stages of the process
Where does Spermatogenesis occurs in human?. Describe the stages of the process
What is menstruation? Mention the specific action of FSH,LH,estrogen and progesterone in
menstrual cycle?
HOTS
13.
14.
15.
16.
17. Suppose the acrosome of mammalian spermatozoa does not function normally, how would it
affect fertilization? Give reasons.
18. An ovum allows the entry of only one sperm at a time. Why?
19. Failure of fertilisation leads to menstruation. Explain
20. Explain why there is no menstrual cycle before puberty , after menopause and during
pregnancy.
21. Fill in the boxes
22. Study the diagram and answer questions that follows:
34
a.What is the role of corpus luteum in menstrual cycle?
b. Why is luteal phase otherwise called as secretory phase?
c. How is estrogen related to menstrual cycle?
d. How does FSH and LH regulate the menstrual cycle?
23 What is the fate of inner cell mass in the blastocyst? Mention their
significance.
24 Label a,b,c in the following diagram.
3
35
Give the term / reason 5
a) Mechanism responsible for parturition.
b) Role of oxytocin during expulsion of the baby out of uterus
c) Why does zona pellucida layer block the entry of additional sperms?
d) Sperm cannot reach ovum without seminal plasma.
e) All copulations do not lead to fertilization and pregnancy
Furnish the technical term for the following: 5
a) Cushion of fatty tissue covered by skin and pubic hair in female
external genitalia.
b) The finger like projections which collect ovum after ovulation
c) The middle thick layer/wall of uterus
d) Semen without sperm
e) The finger-like projections appearing on the trophoblast after
implantation.
36
Chapter-4:REPRODUCTIVE HEALTH
Reproductive Health:
Human reproductive health and sexuality involve great many components and interrelationships.
A total view of human reproductive health is basic to personal well-being as well as to
interpersonal relationships.
Every individual is a unique sexual being.
Adolescents are vivrant, fragile and prone to experimentation and risk taking , as a result they are
the most vulnerable population as far as delinquent behavior and attitude are concerned.
Every decision has its own consequence. Any wrong decision can lead to disastrous consequence,
which in turn can ruin one‘s life.
Sexual adjustment is part of total personality adjustment. Self-esteem is the key to sexual maturity.
Broad based community and institutional support for reproductive health is essential.
Adolescence Reproductive and Sexual Health (ARSH)
Importance of ARSH
reducing specific risky behaviours
theories which explain what influences people's sexual choices and behaviour .
clear, and continuously reinforced message about sexual behaviour and risk reduction .
Provide accurate information about, the risks associated with sexual activity, about contraception
and birth control, and about methods of avoiding or deferring intercourse
Dealing with peer and other social pressures on young people; providing opportunities to practise
communication, negotiation and assertion skills .
Uses a variety of approaches to teaching and learning that involve and engage young people and
help them to personalise the information.
Uses approaches to teaching and learning which are appropriate to young people's age, experience
and cultural background .
Creating a protective and supportive environment.
Avoiding manipulative relationships.
Promoting and protecting the sexual and reproductive rights of adolescents and youth .
37
Methods of birth control
Behavioural methods: Behavioural methods depend on a good knowledge of the menstrual cycle
as well as adequate self control by the couple.
o Coitus Interruptus: 'Interrupted sex". Penis is withdrawn from the vagina just before
ejaculation.
Advantage
No drug,. No interference with normal body functions. Planned pregnancy.
Disadvantage
Dependent almost wholly on the man's self-control. Failure rate high 15 - 18%.
o
Rhythm method or Safe Period: Requires knowledge of the female partner's menstrual
cycle to identify the days on which sexual intercourse is possible without the risk of
pregnancy. Read more ...
o Avoiding vaginal Intercourse: Anal sex, oral sex or sex without penetrating the vagina.
Sexual act occurs between the tightly held thighs of the woman has no risk of pregnancy.
Barrier methods: Barrier placed between the penis and the vagina during intercourse so that the
sperm cannot meet the ovum for fertilization.
o Male Condoms: Male condoms consist of a sheath, usually made of latex that covers the
erect penis during penetration of the vagina. Read more...
o Female Condoms: Not used often. Made of polyurethrane. Consists of a loose sheath
with two rings on either side. The smaller ring is pushed deep into the vagina , larger ring
remains outside on the edge of the vagina. The female condom can be inserted about 8
hours prior to sexual intercourse and can be kept in for about another 12 hours after
intercourse. Can be used more than once during this period.
o Condoms protect against pregnancy as well as sexually transmitted diseases (STDs),
including HIV/AIDS.
o Diaphragm: Vaginal diaphragm small saucer shaped rubber sheath with a metal coil in
its rim which is fitted across the mouth of the uterus (cervix).
o Cervical Cap: Small dome-shaped rubber device fitted on the cervix. Uncomfortable to
apply and is rarely used nowadays.
o Vaginal Sponge: Small polyurethrane round device which needs to be placed inside the
vagina before sexual intercourse. It releases spermicide wich makes sperm inactive .Be
left in place for 8 hours after use and can be used more than once during this time.
The sponge also acts as a barrier contraceptive to some extent since it swells up to fit
across the cervix once it is inside the vagina.
Hormonal Methods: In this method, drugs are used to either prevent ovulation or to prevent
implantation of the embryo after fertilization.
Combined oral contraceptives contain two hormones similar to the natural hormones in a woman‘s
body---an estrogen and a progestin.
38
Working of Birth Control Pill :
Preventing ovulation. In normal menstrual cycle, the pituitary gland secretes the hormones FSH and LH to
stimulate the ovary to release an egg ('ovulation"). When pills are taken, the level of estrogen in the blood
increased. This sends a negative feedback message to the pituitary gland to stop secreting FSH and LH.
The lowered levels of FSH and LH fails to stimulate the ovaries and ovulation is prevented.
The progesterone in the pills make the cervical mucus hostile to the sperm.
.It also work by causing changes that make the endometrium unreceptive to a fertilized ovum if
ovulation and fertilization do take place
o
o
o
o
o
Oral Contraceptive pills: Combined oral contraceptive pills or birth control pills contain
two hormones - estrogen and progesterone. One to prevent ovulation. Second to disrupt
the normal growth of the internal uterine lining (endometrium) so that the embryo cannot
implant in it. Read more...
Centchroman: Non-hormonal non steroidal contraceptive. Function: slow down growth
rate of internal uterine lining and speed up the movement of the embryo so that
implantation cannot occur. Read more...
The Patch: (Ortho Evra). Thin band-aid like patch containing estrogen and progesterone
which should be applied over the skin. It releases the hormones slowly into the skin
through which they are absorbed.
Depo-provera: Injecting a high dose of the hormone progesterone every three months.
prevents ovulation. Disadvantage : irregular bleeding throughout the three months.
Nuvaring: Thin silastic ring inserted into the vagina once every month. Releases the
hormones estrogen and progesterone and prevents ovulation during the menstrual cycle.
Subdermal Implants
Norplant (a registered trademark of The Population Council for levonorgestrel subdermal
implants) set of six small plastic capsules. The capsules are placed under the skin of a
woman‘s upper arm.
Norplant capsules contain aprogestin, similar to natural hormone of a woman‘s body makes.
Hormone released very slowly from all six capsules. Capsules supply a steady, very low
dose. Contain no estrogen.
Capsules thicken cervical mucus making it difficult for sperm. Stops ovulation (release of
eggs from ovaries) in about half of the menstrual cycles after first year of use.
Emergency Oral Contraception
After unprotected sex, emergency oral contraception can prevent pregnancy. Sometimes
called postcoital or ‗morning after‘ contraception.
Mainly stops ovulation (release of egg from ovary). Perhaps also works in other ways. The
sooner emergency control contraceptives used, the better they prevent pregnancy.
Up to 72 hours after unprotected sex, the woman should take 4 low-dose or 2 "standarddose" combined oral contraceptives, and then take another equal dose 12 hours later.
Regular use of emergency contraceptives has serious health hazards.
Vaginal Pessaries, Tablets, Creams or Foams : Contain spermicides which are toxic to the
39
sperm and should be inserted into the vagina just before coitus. Advantage : easy to apply,
do not interfere with coitus , act as lubricants. Disadvantage : not very effective always.
Intra-Uterine Contraceptive Devices (IUCD): IUCDs or IUDs contraceptive devices which are
placed inside the uterus. Usually small, flexible plastic frame. Often has copper wire or copper
sleeves on it. It is inserted into a woman‘s vagina through her uterus. Almost all brands of IUDs
have two strings, or threads, tied to them. The strings hang through the opening of the cervix into the
vagina. A provider can remove the IUD by pulling gently on the strings with forceps.
IUDs work chiefly by preventing sperm and egg from meeting. IUD makes it hard for sperm to
move through the woman‘s reproductive tract. Reduces ability of sperm to fertilize the egg. Could
also prevent the egg from implanting itself in the wall of the uterus.
IUCDs prevent pregnancy by making the endometrium unreceptive to the fertilized ovum.
Stimulates the endometrium to release leukocytes (WBCs) and prostaglandins making it hostile to
the sperm. Causes bizarre and irregular growth of the endometrium. Prevents implantation of a
fertilized ovum.
IUDs like Copper-Ts also come wrapped in copper. The copper is toxic to sperms and is a method
of enhancing the contraceptive effect of the IUDs.
The IUCDs can come in various shapes and sizes.
Lippes Loop: The Lippes loop consists of a thin plastic (or polyethylene)wire bent in a series of
S-shapes. Needs to be straightened when inserted into the uterus but resumes its shape once inside.
l
Lippes loop
Copper-Ts
Copper T: Cu-T common IUCD. T-shaped structure stays inside the uterus with the long arm of
the T along the uterine cavity (endometrium), shorter arms transversely across the upper part of the
endometrium. Copper-Ts contain a copper wire or copper bars of different strengths wrapped
around the arms or the stem. A Copper T 250 has 250 sq mm of copper wire wrapped around it
and is effective for 3 years. The most commonly used IUCD is the Copper T 380.
40
Mirena: Hormone based IUD releases a progesterone called levonorgestrel. Works by affecting
ovulation, affecting the normal growth of the endometrium and by affecting the cervical mucus so
that the movement of sperm obstructed. In United Kingdom, hormone based IUDs are known as
Intra-uterine Systems (IUS).
Surgical Methods: These are more or less permanent methods of contraception.
o Tubal Ligation: Both female tubes tied off and usually cut during tubal ligation to
prevent the sperm from reaching the ovum during intercourse.
o Vasectomy: The two tubes in the males i.e. vas deferens which carry sperm from the
testes to the penis are tied off and cutt.
o Essure: Method in which small micro-inserts are placed at the mouth of the fallopian
tubes Cause scarring and block them. Prevents sperm from reaching the ovum for
fertilization.
PREGNANCY
P occurs when a sperm
produced by a male, fuses
with an ovum produced by a
female.
Every month a mature ovum
released from either one of a
woman‘s two ovaries. Ovum
round and about 100 microns
in diameter, slightly smaller
than the period at the end of
this sentence. Largest cell in
the human body and Only one
visible to the naked eye.
Ovum picked up by the
fallopian tube on the same
side. (There are two fallopian
tubes on either side of the
uterus near the ovaries. See image ). Tubes have long fingerlike projections called fimbria which are used
like hands to pick up the ovum.
The ovum then moves through the tube, propelled by long hairs growing from cells in the tubes. Like grass
bending before the wind, hairs bend towards the uterus in waves, pushing the ovum slowly towards the
uterus.
Egg remains viable, that is, alive for about 72 hours, but is capable of being fertilized for only about 12 24 hours. If it remains unfertilized during this period, it disintegrates in the tube without leaving any trace.
Its end products (mainly proteins) are absorbed into the bloodstream and excreted through the urine or
stool.
41
Fertilization, Implantation and Pregnancy
Sperm however is viable for a longer period, been found in the uterus 5 – 7 days after coitus. Capable of
fertilizing an ovum for only 48 - 72 hours after being ejaculated. Time taken by the sperm to reach the
tubes is between 6 – 12 hours, Sometimes as early as 1 hour.
Intercourse has to take place within this narrow time frame (1-2 days before ovulation or immediately after
ovulation), for a pregnancy to occur. At every intercourse a normal man deposits 2 – 5 mililitre of semen
in the upper part of the vagina (see diagram). Each mililitre of semen contains about 50 – 200 million of
sperms.
Whisking their tails madly, the sperms swim rapidly upwards into the uterus and from there into the two
tubes on either side at the rate of 3mm per hour. It takes an average of 10 hours for the sperm to reach the
tubes.
All the sperm deposited in the vagina cannot swim into the uterus. Some die off in the vagina, some get
entangled in the cervical mucous and some manage to swim just into the cervix before dying. But it is
believed that even these sperms help in causing pregnancy by changing the acidity (‗ph‘) of the vagina or
by acting on the cervical mucous so that other sperms can penetrate it and reach the ovum. Only about 1 %
of the total number of sperms deposited in the vagina make the journey.
Thousands of sperms flood the uterus and both the tubes. Some tumble out of the opening of the tubes into
the abdomen.
Hundreds of sperm (estimated to be around 300) surround the ovum in the tube. They press against the
membrane of the ovum attempting to penetrate it and fertilize the ovum. Finally one sperm succeeds. At
once a chemical reaction is triggered off in the wall of the ovum, making it impenetrable to any other
sperm. No other sperm can enter the ovum now.
42








The unsuccessful sperms slowly degenerate.
The sperm the ovum fuses with it to form zygote. The zygote starts to divide as it is propelled
towards the uterus – dividing Zygote called embryo.
In-vitro fertilization (IVF ovum and the sperm is allowed to fertilize in a laboratory dish (petri
dish). Embryo usually transferred into the mother‘s uterus on 3rd day at the 4 – 8 celled stage.
The zygote reaches the uterus usually on 6th to 9th day after ovulation, Morula a 16-celled.
Separation between 2-celled to 16-celled stages (identical twins). Separation at later stages can
lead to the potentially fatal condition of conjoint twins or Siamese twins.
Morula sticks to the inner lining of the uterus ('endometrium'). Progesterone from ovaries prepares
the endometrium to receive morula.
Morula burrowed deep into endometrium by 9th - 12th day Can cause ‗implantation bleeding‘.
Development of embryo continues until 9th months of pregnancy (40 weeks or 280 days), to form
fully formed baby.
INFERTILITY AND ITS TREATMENT
Infertility:- Woman fails to conceive after one year of sexual life without contraception. According to
(WHO) World Health Organisation, infertility about 10 % worldwide.
Infertility treatment, azoospermia (complete absence of sperm).
Intra-Uterine Insemination (IUI): Used when men has moderately low sperm count. Semen collected
by masturbation, washed and centrifuged to increase the sperm density. Sample injected into the uterus.
Procedure within 2 hours of collection of semen.
o
o
o
Insemination with Husband's Semen (AIH) Impenetrable cervical mucous or diseased
deformed Impotence or premature ejaculation.
Insemination with Donor Semen (AID)
Semen from somebody other than husband.
InVitro Fertilisation (IVF)) is a process by which egg cells are fertilised by sperm (usually 100,000
sperm / ml) outside the womb, in vitro. Process hormonal controll ovulatory process, removing ova (eggs)
letting sperm fertilise in a fluid medium. Fertilised egg (zygote) transferred to the patient's uterus. The first
successful birth of a "test tube baby", Louise Brown, occurred in 1978.
43
In vitro, within the glass, In vivo procedure, tissue remains inside the living organism within which it is
normally found. IVF, also calledtest tube babies,
Zygote intrafallopian transfer (ZIFT) fallopian tubes prevents binding of sperm to egg. Egg cells
removed from ovaries, and in fertilised blocked vitro . Resulting zygote is placed into the fallopian tube by
laparoscopy. Gamete intrafallopian transfer (GIFT). ZIFT success rate 64.8% one cycle – five weeks.
Steps:
Woman to take fertiolity medication – stimulate egg production.
Ovaries follicles mature – woman infected with HCC (human chorionic gonadotropin.
Eggs harvested 36 hours later, by transvaginal ovum retrieval. Fertilization in laboratory resultant early
embryos or zygotes placed woman's fallopian tubes by laparoscope.
Gamete intrafallopian transfer (GIFT) Eggs removed from woman's ovaries, Placed in one Fallopian
tubes, along with the man's sperm. Technique, pioneered by endocrinologist Ricardo Asch, Fertilization
inside the woman's body. [1] Four to six weeks to complete a cycle of GIFT. Harvested egg, mixed with the
man's sperm, placed into the woman's Fallopian tubes using a laparoscope.
Intracytoplasmic Sperm Injection (ICSI): Single sperm injected into centre of the egg, to achieve
fertilization.
Advantage used for men with very low sperm count In azoospermic, men sperm suctioned out of the vas
deferens ( male tubes). Careful testicular biopsy and MESA - Microepididymal sperm aspiration.
Prevention of Male Infertility : Undescended testes treated infancy. Infections by mumps and other
viruses should be managed by medically.
General Facts About STDs
Sexually transmitted diseases STD, or STIs (sexually transmitted infections) are transferred from one
person to another through sexual contact. 25 diseases can be transmitted through sexual activity. E.G.
HIV, chlamydia, gonorrhea, syphilis, genital herpes, human papillomavirus, hepatitis B, trichomoniasis,
and bacterial vaginosis. Risk prone: Adolescents.
Pelvic inflammatory disease, cause infertility. STDs can be prevented by refraining from sexual
activity, some contraceptive devices, such as condoms.
Specific STDs: An Overview
Human Papilloma Virus: Main cause of cervical cancer. Treatment other types of cancers of the female
reproductive system. Reduces signs and symptoms, no cure. HPV vaccine developed.
Herpes Virus: Symptoms Periodical blisters or sores on the genitals.
Hepatitis: Hepatitis B (HBV) vaccine available. Other hepatitis infections through sexual contact include
Hepatitis A and Hepatitis C.
HIV/AIDS: One STD that many people are worried about getting is HIV. While new ways of treating this
44
infection can significantly prolong an infected person's life, for far too many people this infection
eventually progresses to AIDS and, ulitmately, death. More than 40 million people worldwide are
infected with the HIV virus; women account for 50% of those infected. Auto Immuno Deficiency
synotrome, Caused by HIV.
Syphilis: Syphilis can easily be treated and cured. Symptoms can progress and affect the nervous system
and brain leading to dementia and death.
Trichomoniasis:Common, curable STDs.
Common Infections: Chlamydia and gonorrhea often infect a person at the same time. Can be cured
Damage reproductive system if left untreated.
Pubic Lice: Crabs are very similar to head lice. Symptom – itching. Can be treated.
Rare Infections: Granuloma inguinale and chancroid, Well known in North America, Lesser-talked
about STDs nongonococcal urethritis, molluscum contagiosum
KNOW THE SYMPTOMS OF STDs






Swelling or tenderness in genital area.
Blisters ,sores or bumps around the mouth or genitals.
Fever,chills and aches.
Unusual itching.
Burning sensation when you pass urine or move your bowels.
White,watery or yellow disharge from the penis.
Women face special risks






Usually have fewer symptoms than men, often none at all.
Bleeding that is not part of their period.
Pelvic or vaginal pain.
Discharge from the vagina.
Painful urination.
Unusual rash, sore or growth in the genital area.
DON’T LET STDs TO TAKE YOU BY SURPRISE
Pelvic Inflammatory Disease Overview
Pelvic inflammatory disease (PID) is infection of a woman's reproductive organs. Infection spreads upward
from the cervix to uterus, Fallopian tubes, ovaries, and surrounding structures
Symptoms
Lower Abdominal pain or tenderness
Back pain
Abnormal uterine bleeding
Unusual or heavy vaginal discharge
Painful urination
45
Painful sexual intercourse
Symptoms not related to the female reproductive organs include fever, nausea, and vomiting.
PID symptoms may be worse at the end of a menstrual period and during the first several days
following a period.
Ectopic Pregnancy Overview
Pregnancy that develops outside a woman's uterus (womb). Fertilized egg develops somewhere else in the
abdomen especially fallopian tubes, outside of Utres, on ovaries or attached to bowels. Fetuses destroyed.
Usually found in first 5 – 10 weeks of pregnancy.
Complications Intra-abdominal hemorrhage (severe bleeding) rupture of fallopian tube.
Chapter – 5 Genetics
Relationship between genes and chromosome of diploid organism and the terms used to describe them
46
Know the terms
Terms
Meaning
Example
Address/ location of a gene in a chromosome
T,A.b,d etc
Allele
Allelomorphs= alternative form of a gene
T and t OR A and a etc
Homozygous
Both alleles of a gene at a locus are similar
AA or aa
Heterozygous
Both alleles of a gene at a locus are dissimilar
Aa or Tt etc
Homozygous
Dominant
Both alleles of a gene at a locus are similar &
dominant
AA
Homozygous
recessive
Both alleles of a gene at a locus are similar &
recessive
aa
Mendel's first law ( Law of dominance )characters are controlled by discrete units called genes (allele)
which occur in pair .in heterozygous condition only one gene can express it self which is dominant. (Can
be explained by monohybrid cross)
Mendel's second law ( Law of segregation): The two alleles received one from each parent segregate
independently in gamete formation, so that each gamete receives one or the other with equal probability.
(Can be explained by monohybrid cross)
47
Mendel's third law ( Law of recombination): Two characters determined by two unlinked genes are
recombined at random in gametic formation, so that they segregate independently of each other, each
according to the first law (note that recombination here is not used to mean crossing-over in meiosis). (Can
be explained by dihybrid cross)
This is what Mendel said (summary) :
1) Dominant alleles overpower recessive alleles. Dominant traits overpower recessive traits.
2) Rule of segregation (Separation): Gametes (sex cells) only receive one allele from the original gene.
3) Rule of Independent assortment: One trait will not determine the random selection of another.
In complete dominance: When one allele of a gene is not completely dominant over the other and the
F1 hybrids are intermediate between two parents. The phenotypic and genotypic ratio is same.1:2:1
in F2 generation. E.g. Snapdragon or Antirrhinum majus
Co dominance: Two alleles of a gene are equally expressive and dominant in a generation eg Human
blood group
( Note : Human blood group is also an example for multiple allelisim i,e when a gene exists in more than
two allelic form)
Basic outline of Mendels cross
1. Pure breeding parents for a pair of contrasting character (allelic Pair) is taken
e.g, Tall pure-bred pea plants (TT) & short pure-bred pea plants (tt)
2. Gamete formation (Meiosis)
3. Hybridization (crossing is done)
4. F1 generation - the product of the above cross (are called hybrids)
5. Selfing (allowed to self fertilize / self breeding )
6. Gamete formation (Meiosis)
7. F2 generation - the product of the above selfing
48
8. Analysis of result (Phenotype and Genotype)
Tendency of genes of same chromosome to remain together
Such genes are called – linked genes.
Linked genes present only parental types
Figure 1 Schematic diagram of Genetic Linkage and Recombination
(A) Two homologous chromosomes: blue (paternal) and orange (maternal). Three genes with separate
alleles and linkage " noted (A,a; B,b; C,c;).
(B) Crossing over during meiosis. (
(C) Two alleles and their linked genes have switched locations via recombination. Four additional
alleles and their associated (A,a; B,b;) have not switched and are considered linked.
(D) Recombined haploid chromosomes segregate separately during meiosis as gametes before
fertilization.
(E) Sample recombination frequencies between genes demonstrating higher rates of recombination for
genes further apart.
49
Cross
Result of F2 generation
Monohybrid Tt X Tt
3:1
1:2:1
Dihybrid cross
9:3:3:1
1:2:1:2:4:2:1:2:1
1:2:1
1:2:1
YyRr X YyRr
Incomplete dominance
Rr X Rr
Co Dominance and multiple allelisim
Blood group
Possible genotype
A
IAIA OR IAi
B
IBIB OR IBi
AB
IAIB
O
ii
Crosses of blood group ( CO DOMINANCE)
Blood group
Possible genotype
Possible phenotype
AXA
IAIA X IAIA
A
IAIA X IAi
A
IAi X IAi
A;O
IBIB X IBIB
B
IBIB X IBi
B
IBi X IBi
B; O
AB X AB
IAIB X IAIB
AB: A; B
OXO
ii
O
BXB
X ii
50
POSSIBLE BLOOD GROUP OF PROGENY WITH RESPECT TO THE BLOOD GROUP OF
PARENTS
A
B
AB
O
AXA
+
-
-
+
AXO
+
-
-
+
AXB
+
+
+
+
BXB
-
+
-
+
BXO
-
+
-
+
AB X A
+
+
+
-
AB X B
+
+
+
-
AB X O
+
+
AB X AB
+
+
+
-
OXO
-
-
-
+
KEY
-
+ = POSSIBLE
- = NOT POSSIBLE
Sex determination and sex chromosome
Organism
Male
Female
Human beings
XY
XX
Birds
ZZ
ZW
Insects
XO
XX
51
Pedigree Analysis
Pedigree is a chart of graphic representation of record of inheritance of a trait through several generations
in a family
Symbols used
Four patterns of inheritance
52
AUTOSOMAL DOMINANT
1. Traits are controlled by dominant
genes
2. Both males and females are equally
affected
3. traits do not skip generations
4. e.g. polydactyly, tongue rolling ability
etc
AUTOSOMAL RECESSIVE
1. Traits are controlled by recessive
genes and appears only when
homozygous
2. Both males and females are equally
affected
3. Traits may skip generations
4. 3:1ratio between normal and affected.
5. Appearance of affected children from
normal parents (heterozygous)
6. All children of affected parents are also
affected.
7. e.g.- Albinism, sickle cell anaemia etc
X-LINKED DOMINANT
X-LINKED RECESSIVE
1. All daughters of an affected male will
be affected
2. there is no male to male transmission.
3. e.g very rare-Ritts disease
1. Traits is more common in males (since
hemizygous) but rarely in females
(since homozygous)
2. all daughters of a male who has the
trait are heterozygous carriers
4. there is no male to male transmission.
5. affected males receive the trait from
carrier mother who has affected father
6. e.g- haemophilia, colour blindness
53
A 'typical' autosomal recessive pedigree
54
A 'typical' autosomal dominant pedigree
x-chromosome linked pedigree
Now try to answer
1. Is it possible that this pedigree is for an autosomal dominant trait?
2. can two individuals that have an autosomal dominant trait have unaffected children?
3. Is it possible that this pedigree is for an autosomal dominant trait?
4. Is it possible that this pedigree is for an autosomal dominant trait?
55
5. Is it possible that the pedigree above is for an autosomal recessive trait?
6. Assuming that the trait is recessive, write the genotype of each individual next to the symbol
A = normal
a = the trait (a genetic disease or abnormality)
7. Is it possible that the pedigree above is for an autosomal recessive trait?
8. Write the genotype of each individual next to the symbol
9. Is it possible that the pedigree above is for an autosomal recessive trait?
56
10. Is it possible that the pedigree above is for an X-linked recessive trait?
11. Write the genotype next to the symbol for each person in the pedigree
12. Is it possible that the pedigree above is for an X-linked recessive trait?
13. Is it possible that the pedigree above is for an X-linked recessive trait?
14. Is it possible that the pedigree above is for an X-linked recessive trait?
15. Is it possible that the pedigree above is for an X-linked recessive trait?
57
16. Is it possible that the pedigree above is for an X-linked recessive trait?
Clues
Autosomal Dominant
Affected
Unaffected
AA
aa
Aa
Autosomal Recessive
aa
AA
Aa
X- chromosome linked
ecessive
X X
XX
X Y
XX
XY
TERMINOLOGIES
Allele = A factor or letter that makes up a gene. 2 alleles make up one gene. Alternative forms of a genetic
locus; a single allele for each locus is inherited separately from each parent (e.g., at a locus for eye color
the allele might result in blue or brown eyes).
Alleles = "B" and "b" are different alleles.
Autosomal genes = genes that are not found on the sex chromosomes. Autosomal chromosomes are ones
that are not XX and XY. A chromosome not involved in sex determination. The diploid human genome
consists of 46 chromosomes, 22 pairs of autosomes, and 1 pair of sex chromosomes (the X and Y
chromosomes).
Carrier = A person who has a defective gene and a dominant normal gene and therefore, is normal. (Nn)
Centimorgan (cM): A unit of measure of recombination frequency. One centimorgan is equal to a 1%
chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossing
over in a single generation. In human beings, 1 centimorgan is equivalent, on average, to 1 million base
pairs
Chromosomes = 46 are found in human cells. Genes are carried on chromosomes.
58
Clones: Group of cells derived from a single ancestor.
Cystic Fibrosis = Autosomal recessive. Mucous in lungs... Death in the 20s.
DNA = The main instructions that explain how to build the body. (Deoxyribose Nucleic Acid) DNA
makes up alleles, genes and chromosomes.
Dominance = This is one of Johann Gregor Mendel‘s principles. In his studies with pea plants Mendel
notices that pure tall plants bred to pure short plants resulted in tall hybrid plants. Tallness was dominant
over shortness.
Dominant = A allele that overpowers another is dominant.
Down's Syndrome = Due to an extra chromosome. (21st pair).
Gamete = Sperm or egg. Germ Cell. In humans, germ cell contains 23 chromosomes.
Genetics: The study of the patterns of inheritance of specific traits
Gene = Every trait is controlled by a gene. A human has 20,000 genes. Genes are controlled by 2 factors
called ―alleles‖ . Each allele comes from a parent.
Genotype = Hereditary or Genetic constitution of an Organism. (Genes an organism possesses)
Genome: All the genetic material in the chromosomes of a particular organism; its size is generally given
as its total number of base pairs.
Germ Cell- An egg or sperm cell. A gamete. In humans, a germ cell contains 23 chromosomes.
Haploid= A single set of chromosomes (half the full set of genetic material), present in the egg and sperm
cells of animals and in the egg and pollen cells of plants. Human beings have 23 chromosomes in their
reproductive cells.
Hemophilia = Sex-linked recessive. Males get it most often.
Heterozygous = This means alleles of a gene are "different".
Heterozygosity=The presence of different alleles at one or more loci on homologous chromosomes.
Homozygous = When alleles of a gene are "the same"
Homologous chromosomes: A pair of chromosomes containing the same linear gene sequences, each
derived from one parent
Huntington's Chorea = Autosomal Dominant. People die at 40 +... Jerky muscular motions
Hybrid = Means alleles of a gene are "different" (Hh) See heterozygous.
59
Independent Assortment: This is Johann Gregor Mendel‘s 2nd principle. It states that alleles of one gene
separate independently from alleles of another gene. In other words, eye color does not affect a person‘s
ability to roll his or her tongue.
In vivo: Inside living Organism.
In vitro: Outside a living organism in artificial or laboratory conditions.
Karyotype: A photomicrograph of an individuals chromosomes arranged in a standard format showing the
number, size, and shape of each chromosome type;
Linkage: The proximity of two or more genes on a chromosome; the closer together the genes are, the
lower the probability that they will be separated during
meiosis and hence the greater the probability that they will be inherited together.
Linkage map: A map of the relative positions of genetic loci on a chromosome, determined on the basis of
how often the loci are inherited together. Distance is measured in centimorgans (cM).
Locus (pl. loci): The position on a chromosome of a gene or other chromosome marker; also, the DNA at
that position. The use of locus is sometimes restricted to mean regions of DNA that are expressed.( See
gene expression).
Meiosis = The kind of cell division that produces sperm and egg. Meiosis reduces the number of
chromosomes to half. In humans, for instance, the nuclei of body cells contain 46 chromosomes. Due to
meiosis, sex cells(gametes) carry only 23 chromosomes – one chromosome from each homologous pair.
Mendel, Johann Gregor = The father of genetics
Mutation = A change in the DNA instructions. A change in the DNA sequence. The change can be
beneficial, detrimental or neutral. It ultimately results in a change in protein. For instance, random genetic
mutation gave rise to the dark phenotype of the peppered moth.
Non-Disjunction: When homologous chromosomes fail to segregate properly during meiosis. Down
syndrome, Turner syndrome and Klinefelter syndrome result from non-disjunction.
Nucleotide = One of the four DNA chemical submits: (A + sugar and phosphate), (T + sugar and
phosphate), (G + sugar and phosphate), (C + sugar and phosphate). 3 billion nucleotides make
human genome
Phenotype = the way an organism looks.( EXTERNAL CHARACTERISTICS)
Recessive = A small, weaker allele is recessive. (CANNOT EXPRESS ITSELF IN HETEROZYGOUS
CONDITION)
Segregation = This is one of Mendel‘s principles. Mendel said that all genes are comprised of 2 factors,
one from each parent. Chromosomes segregate during meiosis. These factors (alleles) of a gene separate
during the formation of gametes (sperm and egg). This ensures that each parent contributes 50% of their
genetic information.
Sex chromosomes = Chromosomes that determine sex (XY and XX)
Somatic Cell = Body cell that contains 46 chromosomes in humans.
Tay Sachs Disease = Autosomal recessive. Children die young. Head enlarges....
60
Trait = is a feature of an organism.
Uracil = in RNA, this nitrogen base matches with Adenine instead of Thymine.
5. Mutation
Mutations – sudden change in DNA sequences resulting in changes in the phenotype and genotype
Mutagens – that causes mutation (X-ray, UV ray, harmful chemicals etc)
Types of Mutations
Chromosomal mutation
Gene mutation
Structural
I
Numeral
II
III
Point
Frame shift
IV
I - Deletion
II- Duplication (addition)
Euploidy
61
Aneuploidy
III Inversion
IV Translocation
i. triploid (3n)
i. Nullisomy
(2n-2)
ii. Tetraploid (4n)
ii.Monosomy (2n-1)
iii. Pentaploid (5n)
iii Trisomy
(2n+1)
iv. Hexaploid (6n)
iv Tetrasomy (2n+2)
(POLYPLOIDY)
Aneupolidy is due to non disjunction (non separation) of chromosome during meiosis
GENETIC DISORDERS
62
Mendelian Disorder
Chromosomal disorder
Single gene disorder
Involve a chromosome ,its part or complete set of
chromosomes
Follow Mendellian principle of inheritance
Do not follow Mendellian principle of inheritance
Gene disorders (gene mutation & point mutation)
Chromosomal aberrations (breakage deletion
polyploidy and aneuploidy)
GENETIC DISORDERS
AUTOSOMAL
Recessive
X- CHROMOSOME LINKED
Dominant
Recessive
Sickle cell anemia
Polydactyly
Haemophilia
Phenylketonuria
Huntington‘s disease
Colour blindness
Dominant
Very rare e.g.
disease
Rett‘s
Albinism
CHROMOSOMAL DISORDERS
AUTOSOMAL
Down‘s syndrome (trisomy of chromosome
number 21 ) total chromosome 47
X- CHROMOSOME LINKED
Turner‘s syndrome (absence of one X
chromosome) 45,X0
Klinefelter‘s syndrome (presence of an extra X
chromosome) 47,e.g. XXY
Note: I n case of X chromosome linked chromosomal disorders (aneuploidy)
Presence of Y chromosome – phenotype is male
Absence of Y chromosome – phenotype is female
63
Chapter 6. MOLECULAR BASIS OF INHERITANCE
DNA is a polynucleotide. When many nucleotides are linked with each other in a linear fashion, the
resulting chain, is referred to as a polynucleotide (polymer). For example, each strand of DNA molecule
has many deoxyribonucleotides linked in a chain-like arrangement. Therefore, it is described as
polynucleotide strand and DNA molecule as polynucleotide molecule.
In the DNA polynucleotide strands, the nucleotides are joined with each other by ‗phosphodiester
linkages‘ (Figure. 1.).
In a phosphodiester linkage, the phosphate group present at the C-5 of the sugar of one nucleotide gets
attached to the C-3 of the sugar of the next nucleotide in the chain.
(b) The Watson-Crick model of the DNA double helix : The most widely accepted model for the
structure of DNA molecule (Figure 8.4) was proposed by Watson and Crick in 1953 (who won the Nobel
Prize for Medicine in 1962). According to their model, the DNA has the following structural
characteristics.
i. Molecule : The DNA molecule is a double helix (Fig. 1A). The molecule is formed by two antiparallel
polynucleotide strands which are spirally coiled around each other in a right-handed helix. The two strands
are held together by hydrogen bonds. The double stranded helical molecule has alternate major (or deep)
and minor grooves.
Fig 8.4
Figure
1.
Structure
of
DNA
(Watson
and
Crick
model)
(A) DNA double helix. (B) Detailed structure of the two strands. (C) C-5 and C-3 ends and
antiparallel nature of strands (diagrammatic)
ii. Structure of each strand (8.4 B) : Each strand is a long polynucleotide of deoxyribonucleotides. The
backbone of the strand is formed by alternately arranged deoxyribose sugar and phosphate molecules
64
which are joined by the phosphodiester linkages. Each sugar in the strand has one base horizontally
attached to it at carbon-1. It can be any one of the four: A,T,G,or C. These four N-bases can occur in any
possible sequence along the length of a strand.
iii. Complementary nature of the strands : The two strands are complementary to each other with
regards to the arrangement of the bases in the two strands. For example, where adenine (a purine) occurs in
one strand, thymine (a pyrimidine) is present in the corresponding position in the opposite strand and vice
versa. Similarly, wherever guanine (a purine) is present in one strand, the other strand has cytosine (a
pyrimidine) opposite to it and vice versa. Thus, in the double helix, purines and pyrimidines exist in base
pairs, i.e., (A and T) and (G and C). As a result, if the base sequence of one strand of DNA is known, the
base sequence of its complementary strand can be easily deduced.
vi. Complementary base pairing : In each pair, the two bases of the opposite strands are joined by
hydrogen bonds. A and T are joined by two hydrogen bonds, while G and C are joined by three hydrogen
bonds. This is called complementary base pairing. The two strands are thus held together all along their
lengths by these hydrogen bonds.
v. Purine : Pyrimidine ratio : Because of the fixed or complementary base pairing in the DNA molecule,
the total number of A is equal to the total number of T and the total number of G is equal to the total
number of C. In other words, (A+G)= (T+C). Hence, purines: pyrimidines ratio is 1:1.
vi. C-3 and C-5 ends of the strand : In each strand one end of the strand has one free phosphate group on
carbon-5 of the sugar molecule. This is the end of the strand is called C-5 (or 5') end. The other end of the
strand has a free -OH on carbon-3 of the sugar molecule. This is called C-3 (or 3') end of the strand (Figure
1c).
vii. Antiparallel nature of strands: The two strands are oppositely oriented and hence are called
antiparallel. This means, the 3' end of one strand is adjacent to the 5' end of the other strand (Fig. 8.4c) .
This is because, the phosphate-sugar linkages run in opposite directions in the two strands.
viii. Dimensions: The diameter of the DNA double helix is 20 Ao. The length of each complete spiral (turn
or pitch) of the molecule measures 34 Ao. 10 pairs of nucleotides are present in each complete spiral.
Therefore, each nucleotide in the strand occupies a distance of 3.4A0.
(c) Circular DNA molecules : Chromosomes of most prokaryotes (e.g. bacteria, cyanobacteria,) are
circular molecules of DNA.
In bacteria, there is no organized nucleus. The bacterial nucleoid consists of a single circular DNA
molecule (bacterial chromosome). The molecule has two complementary strands forming a covalently
closed circle. Generally, the circular molecule is present in a highly folded and suspercoiled state (Figure
8.5A). This is expected because the diameter of a bacterial cell (e.g. Escherichia coli) is about 1-2 microns
while the total length of the circular DNA is about 1100 microns. The circular molecule has 40-50 folds or
looped domains. These folds are held in position by RNA molecules (RNA connectors) and some nonhistone proteins associated with the bacterial chromosome. (Histones are absent in bacteria
The DNA segment in each loop is supercoiled independently. Because of this characteristic formation of
loops as well as the supercoils within the loops, the large circular DNA molecule can be packed into a
65
small bacterial cell. Otherwise, the relaxed and fully expanded circular molecule (Figure 8.5) would be
too large (about 350 microns diameter) to be contained in the bacterial cell. The coils of the supercoiled
circle can be relaxed by treatment with enzymes such as RNAse or DNAse. The uncoiling occurs due to a
break (nick) in one or both the strands of DNA.
In some viruses, e.g. certain bacteriophages, the circular DNA is single stranded. It becomes double
stranded only during replication (replicatable form).
8.1 Packaging of Hereditary Material
Structure of nucleus (A) in a prokaryotic cell and (B) in an eukaryotic cell
REPLICATION:The various steps involved in this process are summarized as follows:
i.
ii.
iii.
iv.
v.
vi.
The mechanism of replication starts at a specific point of the DNA molecule. This is called the
origin of replication (orisite)
At the origin, the DNA strand breaks because of an incision (nick). This is made by an enzyme
called incision enzyme (endonuclease).
The hydrogen bonds joining the two strands are broken by the enzyme.
The two strands start unwinding. This takes place with the help of a DNA unwinding protein.
The two polynucleotide strands are thus separated.
The point where the two strands separate appears like a fork or a y-shape. This is described as a
replicating fork.
A new strand is constructed on each old strand. This takes place with the help of a small RNA
primer molecule which is complimentary to the DNA at that point. Each old DNA strand acts as a
template (site) for the construction of new strand. The RNA primer attaches itself to the old strand
and attracts the enzymes which add new nucleotides. The deoxyribose nucleotides are present in
the surrounding nucleoplasm. Appropriate nucleotides are selected from the nucleoplasm, and are
attached by H-bonds to their respective complementary bases on the old strand. A new DNA
strand is thus constructed opposite to each old strand
66
As stated earlier, chromosomes are the carriers of the hereditary material. In cells, chromosomes are
located in the nucleus. In prokaryotic cells (e.g., bacteria, cyanobacteria, etc.), organized nuclei are not
present. As a result, the hereditary material occurs in the cell cytoplasm as a nucleoid (Figure 8.1-A)
without the nuclear envelope.
(a) Eukaryotic nucleus (Figure 8.1-B): In eukaryotic cells (e.g., all higher plants and animals), a well
organized nucleus is present. It is bounded by a double membrane nuclear envelope with trilaminar
structure. There are pores in the envelope. Internally, the nucleus is filled with nucleoplasm (nuclear sap)
that is acidophilic and clear. The interphasic nucleus (i.e. the nucleus which is not in the stage of division)
usually shows the presence of one dark, spherical body called nucleolus. The nucleoplasm also contains
nuclear reticulum or chromatin network. It consists of very fine, long chromatin fibers. These represent the
chromosomes at the interphasic stage. They become short, thick and distinct during cell division.
(b) Structure of chromatin (Figure 8.2): The chromosomes are composed of nucleoprotein called
chromatin. The chromatin fiber appears to have a structure like a ‗string of beads.‘ According to the
nucleosome-solenoid model proposed by Kornberg and Thomas (1974), the beaded string is made of
repeating units called nucleosomes (Figure 8.2A). Each nucleosome is a bead-like particle about 60 Ao
high and 110 Ao wide.
Figure 8.2. Nucleosome - solenoid model for the structure of chromatin
In the nuclesome, the DNA double helix is wound around the core of eight histone molecules (octamer).
The segments of DNA joining the ‗beads‘ are called linker DNA. Each linker DNA has an average of one
molecule of a histone protein (H1) attached to it.
The thin, long and "beads-on-string" chromatin fiber is condensed and packed into a short and thick
chromosome (metaphase chromosome) because of further coiling and "super coiling", wherein (1) the
string of beads condenses and coils to produce a 100 Ao thick nucleosome fiber (2) the nucleosome fibre
then supercoils to produce a 300-350 Ao thick solenoid fiber. A solenoid represents the structure of
chromatin fiber in the metaphase chromosome.
8.2 The Structure of DNA
67
Deoxyribonucleic nucleic Acid (DNA) is a highly complex megabiomolecule. The long chain molecule is
formed of repeating units called nucleotides. Hence, it is described as the polynucleotide molecule. It
consists of two polynucleotide antiparallel strands which are spirally coiled round each other along their
lengths (Watson and Crick, 1953).
(a) Chemical Components of DNA : The highly complex DNA molecule is composed of only three types
of chemical
components. These are (i) deoxyribose sugar, (ii) a phosphate, and (iii) nitrogen containing organic bases.
i.
ii.
iii.
Deoxyribose sugar : The sugar present in the DNA molecule is called deoxyribose sugar and
hence the nucleic acid is called deoxyribonucleic acid (DNA). It is a pentose sugar (with 5 carbon
atoms) having a pentagonal ring structure (Figure 8.3)
Phosphate (Figure 8.3) : The phosphate in the DNA is present as phosphoric acid (H3PO4). It
has three reactive (-OH) groups of which two are involved in the formation of the sugar-phosphate
backbone of each DNA strand.
The nitrogen-containing organic bases
These are heterocyclic compounds containing nitrogen in their rings and therefore called nitrogenous
bases. DNA contains four different bases called adenine (A), guanine (G) cytosine (C), and thymine (T).
These are grouped into two classes on the basis of their chemical structure: (i) Purines (with a double ring
structure) and (ii) Pyrimidines (with a single ring structure) (Figure 8.3)
Nucleosides : In the molecules of nucleic acids (DNA and RNA), each pentose sugar molecule has one
nitrogen base attached at carbon number 1. It may be either a purine or a pyrimidine base. Thus, a pentose
sugar with the attached N-base forms a nucleoside.
[Sugar + N-base] = Nucleoside.
In DNA, the deoxyribose sugar has one of the four bases (A,G,T or C) attached. Therefore, the nucleosides
in DNA are called deoxyribosides.
[deoxyribose sugar + N-base] = Deoxyriboside
Nucleotides : A nucleoside with a phosphate group attached to it is called a nucleotide
68
Fig.8.3 Chemical components of DNA and the phosphodiester linkage
.
[Nucleoside + Phosphate] = Nucleotide
A nucleotide is the basic unit or monomer in the structure of a nucleic acid molecule.
Thus, a nucleotide is a nucleoside phosphate. In a nucleotide, the phosphate group is linked with the
pentose sugar at carbon-5.
In the DNA, each nucleotide is called deoxyribonucleotide.
[Deoxyribose sugar + N-base + Phosphate] = Deoxyribonucleotide
As there are four different bases (A,T,G and C) in DNA, there can be only four types of nucleotides in
DNA.
The nucleotides act as the building block molecules for the synthesis of the polynucleotide molecules.
When two nucleotides are linked together, a dinucleotide (or dimer) results.
69
8. 3 Replication Of DNA In Eukaryotes
Definition: "The process by which DNA produces daughter DNA molecules which are exact copies of the
original DNA is called replication of DNA."
In eukaryotes, DNA is double stranded. The two strands are complementary to each other because of their
base sequences.
Semi-conservative method of DNA replication
Important points:
(i) This is the most common method of DNA replication.
(ii) It takes place in the nucleus where the DNA is present in the chromosomes.
(iii) Replication takes place in the S-phase (synthesis phase) of the interphase
nucleus.
(iv) The deoxyribose nucleotides needed for the formation of the new DNA strands are present in the
nucleoplasm.
At the time of replication, the two strands of DNA first separate. Each strand then acts as a template for
the formation of a new strand. A new strand is constructed on each old strand, and two exactly identical
double stranded DNA molecules are formed. In each new DNA molecule, one strand is old (original)
while the other is newly formed. Hence, Watson and Crick described this method as semi-conservative
replication.
(A) An overall process of DNA replication showing replication fork and formation of new strands template
and lagging template
70
Figure Stages in the semi-conservative method of DNA replication in eukaryotes
The various steps involved in this process are summarized as follows:
i.
The mechanism of replication starts at a specific point of the DNA molecule. This is called the
origin of of replication (ori site)
ii.
At the origin, the DNA strand breaks because of an incision (nick). This is made by an enzyme
called incision enzyme (endonuclease).
iii.
The hydrogen bonds joining the two strands are broken by the enzyme.
iv. The two strands start unwinding. This takes place with the help of a DNA unwinding
v.
enzyme(unwindase)
Helicases. The two polynucleotide strands are thus separated.
v.
The point where the two strands separate appears like a fork or a Y-shape. This is described as a
replicating fork.
vi.
A new strand is constructed on each old strand. This takes place with the help of a small RNA
primer molecule which is complimentary to the DNA at that point. Each old DNA strand acts as a
template (site) for the construction of new strand. The RNA primer attaches itself to the old strand
and attracts the enzymes(DNApolymeraseIII) which add new nucleotides through base
complementation. The deoxyribose nucleotides are present in the surrounding nucleoplasm.. A
new DNA strand is thus constructed opposite to each old strand
vii.
viii.
ix.
x.
The formation of new complementary strand always begins at the 3' end of the template strand
(original strand) and progresses towards the 5' end (i.e in 3' - 5' direction). Since the new strand is
antiparallel to the template strand, it is obvious that the new strand itself is always developed in
the, 5'-3' direction. For this reason when the two original strands separate (then with respect to the
origin of separation), one acts as 3'-5' template while the other acts as 5'- 3' template. Of the two,
the replication of 3'-5' template begins first. Hence the new strand formed on it is called the
leading strand. The other template (5'-3') must begin replication at the fork and progress back
toward the previously transcribed fragment. The new strand formed on it is called the lagging
strand.
Replication of the lagging strand takes place in small fragments called Okazaki fragments. These
are then connected together by the enzyme ligase.
Replication may take place in only one direction on the DNA helix (unidirectional) or in two
directions (bidirectional).
At the end of the process, two double stranded DNA molecules are formed from the original DNA
molecule.
71
xi
In each newly formed DNA, one strand is old(parental) while the other is new. Hence, it is
described as semi-conservative replication.
It is very important to know that DNA replication is not a passive and spontaneous process. Many
enzymes are required to unwind the double helix and to synthesize a new strand of DNA. We will
approach the study of the molecular mechanism of DNA replication from the point of view of the
machinery that is required to accomplish it. The unwound helix, with each strand being synthesized into a
new double helix, is called the replication fork.
The Enzymes of DNA Replication
Topoisomerase is responsible for uncoiling of double halix. The tension holding the helix in its
coiled and supercoiled structure can be broken by nicking a single strand of DNA. Try this with
string. Twist two strings together, holding both the top and the bottom. If you cut only one of
the two strings, the tension of the twisting is released and the strings untwist.
Helicase accomplishes unwinding of the original double strand, once supercoiling has been
eliminated by the topoisomerase. The two strands very much want to bind together because of
their hydrogen bonding affinity for each other, so the helicase activity requires energy (in the
form of ATP ) to break the strands apart.
DNA polymerase proceeds along a single-stranded molecule of DNA, recruiting free dNTP's
(deoxy-nucleotide-triphosphates) to hydrogen bond with their appropriate complementary dNTP
on the single strand (A with T and G with C), and to form a covalent phosphodiester bond with
the previous nucleotide of the same strand. The energy stored in the triphosphate is used to
covalently bind each new nucleotide to the growing second strand. There are different forms of
DNA polymerase , but it is DNA polymerase III that is responsible for the processive synthesis of
new DNA strands. DNA polymerase cannot start synthesizing de novo on a bare single strand. It
needs a primer with a 3'OH group onto which it can attach a dNTP. DNA polymerase is actually an
aggregate of several different protein subunits, so it is often called a holoenzyme. The
holoenzyme also has proofreading activities, so that it can make sure that it has inserted the
right base, and nuclease (excision of nucleotides) activities so that it can cut away any
mistakes it might have made.
Primase is actually part of an aggregate of proteins called the primeosome. This enzyme attaches
a small RNA primer to the single-stranded DNA to act as a substitute 3'OH for DNA polymerase to
begin synthesizing from. This RNA primer is eventually removed by RNase H and the gap is filled
in by DNA polymerase I.
Ligase can catalyze the formation of a phosphodiester bond given an unattached but adjacent
3'OH and 5'phosphate. This can fill in the unattached gap left when the RNA primer is removed
and filled in. The DNA polymerase can organize the bond on the 5' end of the primer, but ligase is
needed to make the bond on the 3' end.
Single-stranded binding proteins are important to maintain the stability of the replication fork.
Single-stranded DNA is very labile, or unstable, so these proteins bind to it while it remains single
stranded and keep it from being degraded.
72
The
Steps
of
DNA
Replication
A portion of the double helix is unwound
by a helicase.
A molecule of DNA polymerase binds to
one strand of the DNA and begins
moving along it in the 3' to 5' direction,
using it as a template for assembling a
leading strand of nucleotides and
reforming a double helix.
Because DNA synthesis can only occur 5'
to 3', a second DNA polymerase molecule
is used to bind to the other template
strand as the double helix opens. This
molecule must synthesize discontinuous
segments of polynucleotides (called
Okazaki fragments). Another enzyme,
DNA ligase then stitches these together
into the lagging strand
Speed
of
Replication
Prokaryotes - The single molecule of DNA that is the E. coli genome contains 4.7 x 106 nucleotide
pairs. DNA replication begins at a single, fixed location in this molecule, the replication origin,
proceeds at about 1000 nucleotides per second, and thus is done in no more than 40 minutes.
And thanks to the precision of the process (which includes a "proof-reading" function), the job is
done with only about one incorrect nucleotide for every 109 nucleotides inserted. In other
words, more often than not, the E. coli genome (4.7 x 106) is copied without error!
Eukaryotes - The average human chromosome contains 150 x 106 nucleotide pairs which are
copied at about 50 base pairs per second. The process would take a month (rather than the hour
it actually does) but for the fact that there are many replication origins on the eukaryotic
chromosome. Replication begins at some origins earlier in S phase than at others, but the process
is completed for all by the end of S phase. As replication nears completion, "bubbles" of newly
replicated DNA meet and fuse, finally forming two new molecules
. The semi-conservative nature of DNA replication was confirmed by Meselson and Stahl (1958) with
the help of an experiment. They marked the DNA in Esherichia coli with heavy isotope of nitrogen (15N)
and then traced it in the following generations of the E-coli progeny. It was demonstrated that each
daughter DNA has one strand of the parent (old strand) and the other strand in newly formed.
73
Nitrogen is a major constituent of DNA. 14N is by far the most abundant isotope of nitrogen, but
DNA with the heavier (but non-radioactive) 15N isotope is also functional.
E. coli were grown for several generations in a medium with 15N. When DNA is extracted from
these cells and centrifuged on a salt(CesiumChloride) density gradient, the DNA separates out
at the point at which its density equals that of the salt solution. The DNA of the cells grown in
15
N medium had a higher density than cells grown in normal 14N medium. After that, E. coli cells
with only 15N in their DNA were transferred to a 14N medium and were allowed to replicate; the
progress of cell division was monitored by measuring the optical density of the cell suspension.
DNA was extracted periodically and was compared to pure 14N DNA and 15N DNA. After one
replication(20minutes), the DNA was found to have close to the intermediate density.
Semiconservative replication would result in double-stranded DNA with one strand of 15N
DNA, and one of 14N DNA.
74
The authors continued to sample cells as replication continued. DNA from cells after two replications(after
40minutes) had been completed was found to consist of equal amounts of DNA with two different
densities, one corresponding to the intermediate density of DNA of cells grown for only one division in 14N
medium, the other corresponding to DNA from cells grown exclusively in 14N medium. The result was
consistent with the semiconservative replication hypothesis.
8.6 RNA : Structure and Types
Ribonucleic Acid (RNA) is another polynucleotide which occurs in the cells as non-genetic material, with
the exception of some viruses. RNA is present in the nucleus as well as in the cytoplasm.
General structure
RNA molecule is single stranded and consists of nucleotides arranged in a long series. The single strand of
RNA may be simple and straight, or it may be variously folded upon itself in certain regions.
Structural components : RNA molecule has three primary components.
1. Ribose sugar (a pentose sugar), with a pentagonal ring structure
2. Phosphate, as phosphoric acid
3. Nitrogenous bases
There are four kinds of nitrogenous bases found in RNA. Of those, two are purines and two are
pyrimidines, as follows :
Thus in RNA, uracil is present in place of thymine found in DNA.
Structure of an RNA strand : The strand is made up of alternating molecules of ribose sugar and the
phosphate. The nitrogen bases are attached to the sugar molecules in the strand and ‘stick out‘ laterally as
in DNA (figure 8.9). A sugar, a N-base and a phosphate together form a ribonucleotide. A nucleotide
without the phosphate is called ribonucleoside.
RNA being single stranded, the nitrogen bases remain mostly unpaired. However, the strand may be folded
upon itself in certain regions. In such folded regions, base pairing occurs between purines and pyrimidines
as follows :
75
Adenine = Uracil (two H-bonds). Guanine ≡ Cytosine (three H-bonds). Nitrogen bases remain unpaired in
the unfolded regions of the strand. Because of this variability in base pairing in different regions of the
same strand, the total number of purines need not be equal to the total number of pyrimidines in RNA
Types of non-genetic RNA and their functions
There are three types of non-genetic RNA.
(1) mRNA or messenger RNA, (2) rRNA or ribosomal RNA and (3) tRNA or transfer RNA
(1) mRNA (Messenger RNA) : This is called messenger RNA because it carries information for
protein synthesis from the DNA to the ribosomes in the cytoplasm (the site of protein synthesis). mRNA constitutes about 3-5% of the total RNA. It is produced on the DNA strand. The process is called
transcription. Hence, the base sequence of mRNA is complementary to that of the DNA strand. The bases
on the mRNA strand are organized into triplets. Each triplet consists of a sequence of three consecutive
bases (nucleotides) and is called a codon (code word). Each codon specifies one amino acid. The sequence
of codons on the mRNA strand is called the mRNA language. It indicates the sequence of amino acids for
the synthesis of a protein. It begins with the codon AUG (initiation codon or starting codon) and ends
with either UAA, UAG or UGA (stop codons). The single-stranded mRNA molecule is always straight
(Fig. 8.10) and therefore, base pairing is totally absent in mRNA.
Role of m-RNA in protein synthesis
i.
ii.
iii.
Represents the sequence of codons from the DNA strand (transcription).
Brings the sequence to the ribosomes (site of protein synthesis) in the cytoplasm.
Provides the sequence for the synthesis of specific protein from the amino acids with the help of tRNA (translation).
(2) rRNA (Ribosomal RNA) : r RNA forms about 80% of the total RNA. It is present in the ribosomes in
the cell cytoplasm (site of protein synthesis) and hence called rRNA. The single-stranded molecule of
rRNA is variously folded and twisted upon itself in certain regions (Figure 8.11). In such folded regions,
complementary bases form pairs and are joined by hydrogen bonds.
Role of rRNA in protein synthesis : The role of rRNA in protein synthesis is not yet very clearly known
but it is known to complex with various protiens. The resulting structure is a ribosome, and this complex
reads the coded sequence in mRNA to link amino acids together into particular protiens.
i.
ii.
iii.
It provides proper binding sites for the mRNA of the ribosomes.
It orients the mRNA in such a way that its nitrogen base triplets or codons are properly read or
translated.
It also releases tRNA after the transfer of activated amino acid.
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iv.
v.
It protects the mRNA strand from the action of enzymes (nucleases).
It protects the growing (nascent) polypeptide chain from proteolytic enzymes.
(3) tRNA (Transfer RNA) : It is the smallest of all the types of RNA. About 10 to 20% of the total RNA
of the cell is of this type. tRNA strand is folded upon itself forming loops. It results in either a clover leaf
pattern or hair pin pattern (Figure 8.12). One end of the strand has guanine, while the other end carries
the CCA combination of nitrogen bases. A triplet of nitrogen bases called anticodon is present on one of
the loops. The anticodon pairs with the complementary codon on the mRNA molecule. The tRNA
molecules carry amino acids to the mRNA during the process of protein synthesis. Each type of the
amino acid is carried by a specific tRNA molecule. tRNA is synthesized on the DNA template. It has
complementary base pairs in folded regions.
Role of tRNA in protein synthesis
i.
ii.
iii.
tRNA carries the required specific amino acids from cell cytoplasm to the ribosome (site of protein
synthesis).
Each type of amino acid is carried by a specific type of tRNA.
In the ribosome, tRNA helps to arrange the amino acids in their proper sequence for the synthesis
of a protein. This is done with the help of the codons on the mRNA and the matching
(complementary) anticodons on the tRNA (translation).
CLOVERLEAF STRUCTURE OF tRNA
Table 8.2 : Difference between DNA and RNA
Characters
DNA
RNA
1.
Molecule
Double stranded,
helical
Single stranded,
straight
or
variously folded
and twisted.
2.
Pentose sugar
Deoxyribose
Ribose
3.
Pyrimidine
base
Thymine
Uracil
4.
Complementary
Always present
Normally absent,
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base pairing
and
exists but
may
be
between A = T present in twisted
and G = C
segments of a
molecule.
If present, pairing
is between A = U
and G = C
5.
Ratio
of
Purines:
Pyrimidines
Always 1 : 1
Not
1:1
necessarily
6.
Replication
Can replicate
Cannot replicate
CLOVERLEAF STRUCTURE OF tRNA
The main principle of protein synthesis. According to Crick (1958), DNA determines the sequence of
amino acids in a polypeptide (protein) through mRNA. This is the main principle (central dogma) of
protein synthesis. This involves transcription and translation.
Components involved in protein synthesis : The process requires
1.
2.
3.
4.
5.
The 20 types of amino acids that are specified by the genetic code.
DNA (to provide the base sequence).
The non-genetic RNAs (m-RNA, t-RNA and r-RNA).
Ribosomes (site of protein synthesis) and
Various enzymes (f0actors).
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Mechanism of protein synthesis
As stated earlier, the mechanism of protein synthesis involves two main events namely (A) Transcription
(B) Translation.
(A) Transcription
Transcription is the process of formation of mRNA on the DNA strand. It takes place in the presence of
enzyme RNA Polymerase.
One of the strands of DNA acts as a template for the formation of the same m-RNA in a series, one by one.
Such ribosomes bound to the same mRNA strand are called polyribosomes or polysomes. The
polypeptide chain formation in each ribosome is independent and the same as described above.
Transcription is the first stage of the expression of genes into proteins. In transcription, a mRNA
(messenger RNA) intermediate is transcribed from one of the strands of the DNA molecule. The RNA is
called messenger RNA because it carries the 'message' or genetic information from the DNA to the
ribosomes, where the information is used to make proteins. RNA and DNA use complementary coding,
where base pairs match up, similar to how the strands of DNA bind to form a double helix. One
difference between DNA and RNA is that RNA uses uracil in place of the thymine used in DNA. RNA
polymerase mediates the manufacture of an RNA strand that complements the DNA strand. RNA is
synthesized in the 5' -> 3' direction (as seen from the growing RNA transcript).
The Transcription Process
RNA synthesis involves separation of the DNA strands and synthesis of an RNA
molecule in the 5' to 3' direction by RNA polymerase, using one of the DNA
strands as a template.
In complementary base pairing, A, T, G, and C on the template DNA strand specify U, A, C,
and G, respectively, on the RNA strand being synthesized.
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In a prokaryotic cell, transcription and translation are coupled; that is, translation
begins while the mRNA is still being synthesized. In a eukaryotic cell,
transcription occurs in the nucleus, and translation occurs in the cytoplasm.
Prokaryotic Cell
Because there is no nucleus to separate the processes of transcription and translation,
when bacterial genes are transcribed, their transcripts can immediately be translated.
Eukaryotic Cell
Transcription and translation are spatially and temporally separated in eukaryotic cells; that
is, transcription occurs in the nucleus to produce a pre-mRNA molecule.
The pre-mRNA is typically processed to produce the mature mRNA, which exits the nucleus
and is translated in the cytoplasm
mRNA in Eukaryotes
The sequence of a eukaryotic protein-coding gene is typically not colinear with
the translated mRNA; that is, the transcript of the gene is a molecule that must
80
be processed to remove extra sequences (introns) before it is translated into the
polypeptide.
Most eukaryotic protein-coding genes contain segments called introns, which break up the
amino
acid
coding
sequence
into
segments
called
exons.
The
transcript
of
these
genes
is
the
pre-mRNA
(precursor-mRNA).
The pre-mRNA is processed in the nucleus to remove the introns and splice the exons
together into a translatable mRNA. That mRNA exits the nucleus and is translated in the
cytoplasm.
Pre-mRNA Processing (Splicing)
Eukaryotic pre-mRNAs typically include introns. Introns are removed by RNA
processing in which the intron is looped out and cut away from the exons by
snRNPs, and the exons are spliced together to produce the translatable mRNA.
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The steps of pre-mRNA splicing (intron removal) are as follows:
• The intron loops out as snRNPs (small nuclear ribonucleoprotein particles, complexes of
snRNAs
and
proteins)
bind
to
form
the
spliceosome.
•
The
intron
is
excised,
and
the
exons
are
then
spliced
together.
• The resulting mature mRNA may then exit the nucleus and be translated in the
cytoplasm.
(B) Translation
In Translation one particular group gets transmitted from one Band of DNA to another Band of DNA. In
this procedure the DNA polymer (enzyme) is used. Normally, 40% of protein synthesis occurs in this
manner.
The genetic code : DNA is genetic material and contains genetic information. The expression of a gene
takes place through specific enzymes. Each gene produces a specific (one-gene one-protien hypothesis). In
other words, formation of each specific protein is controlled by a particular gene. A gene is (almost
always) a segment of DNA strand and so, the information for the formation of a protein is contained in the
DNA strand.
Further, each protein is a long polypeptide chain molecule formed by joining amino acid molecules. From
the cell pool, only 20 different types of amino acids are used for protein synthesis.
The sequence of the nitrogen bases in the DNA determines the sequence of amino acids in a protein
molecule through the mRNA. This sequence is copied down by the mRNA (transcription). It is present on
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the mRNA strand in the form of coded language (cyptogram or mRNA language or genetic code). The
mRNA bases (A, U, C and G) serve as the four alphabets of the coded language.
Codon : The smallest sequence of the nitrogen bases (nucleotides) on the mRNA which can specify one
amino acid is called a codon . Each codon consists of three successive bases on the mRNA.
Why should each codon in the genetic code consist of 3 bases (triplet codon) and not of one base each or
2 bases each? This is because there are 20 different amino acids which can be used in the synthesis of
proteins in the cells. There must be at least one specific codon for each amino acid. Thus, there has
to be at least 20 different codons in the genetic code. There are only four bases. A minimum of 3
bases per codon is necessary to have (a minimum of) 20 codes.
The wobble hypothesis (Crick, 1966) : The anticodon on tRNA is complementary to the codon on the
mRNA as per the A = U, G = C base pairing rule. However, it has been observed that the 3rd base
position may vary and yet still code for the same amino acid. For example, both codons TTA and TTG
code for the amino acid, leucine. Thus, the third position is called the wobble position.
Thus, Crick‘s (1966) wobble hypothesis explains the degeneracy of the genetic code at the third position of
the codon.
8.8 The Central Theme of Protein Synthesis
A protein is a long chain polypeptide. The chain molecule is formed by joining amino-acid molecules with
peptide linkages. The sequence of amino acids in each type of protein is highly specific. The functional
proteins form enzymes and hormones and control all metabolic and biochemical reactions and processes in
cells. Any alteration in the sequence of amino acids in protein molecules can affect the function of that
protien. Hence, bio-synthesis of proteins is a highly specific process.
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SUMMARY : MOLECULAR GENETICS AND GENE EXPRESSION
(1) DNA is the genetic material in almost all organisms. (2) Chromosomes carry genes. (3) The chromatin
consists of DNA and two types of proteins (histones and non-histones). (4) During prophase of the cell
division, DNA of the chromatin undergoes coiling, super coiling and folding and along with the associated
proteins, forms highly a condensed and prominent chromosome (as seen during metaphase). (5) This is
explained with the help of necleosome solenoid model (Komberg and Thomas, 1974). (6) DNA molecule
has a double stranded, helical structure in which the two antiparallel polynucleotide strands are helically
coiled round each other, and joined by hydrogen bonds (Watson and Crick). (7) DNA has the ability of
self-replication. (8) RNA molecule is single stranded. It can not replicate. It is produced on DNA strand.
(9) Non-genetic RNA is of 3 types and helps in protein synthesis. (10) In prokaryotes, the single circular
chromosome has a circular DNA capable of replication. (11) Prokaryotes also possess plasmids and
episomes. These are the extra chromosomal circular DNA which carry genes and are capable of selfreplication. (12) Genetic information required to produce a protein is called the genetic code. It is present
on the DNA in the form of the base sequence. It is transcribed on m-RNA and is then used for synthesis of
protein in the ribosomes. (13) Genetic code is triplet. (14) Each triplet or codon on m-RNA specifies one
amino acid. (15) In all, there are 64 codons in the genetic code of which 61 codons specify 20 different
amino acids. (16) Three codons (UAA, UAG and UGA) do not specify any acid (stop codons). (17) AUG
is the starting or initiation codon. (18) In protein synthesis, m-RNA provides the sequence of the
arrangement of amino acids in form of the codon sequence. These are carried by the t-RNA and are
arranged in the sequence with the help of matching anticodons on t-RNA. (19) After formation, the peptide
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chain is released with the help of release factors.
Griffith's Transformation Experiment
Griffith's experiment, conducted in 1928 by Frederick Griffith, was one of the first experiments
suggesting that bacteria are capable of transferring genetic information through a process known as
transformation.
Griffith used two strains of Diplococcus pneumoniae (which infects mice), a type III-S (smooth) and type
II-R (rough) strain. The III-S strain covers itself with a polysaccharide capsule that protects it from the
host's immune system, resulting in the death of the host, while the II-R strain doesn't have that protective
capsule and is defeated by the host's immune system. A German bacteriologist,
In this experiment, bacteria from the III-S strain were killed by heat, and their remains were added to II-R
strain bacteria. While neither alone harmed the mice, the combination was able to kill its host. Griffith was
also able to isolate both live II-R and live III-S strains of pneumococcus from the blood of these dead mice.
Griffith concluded that the type II-R had been "transformed" into the lethal III-S strain by a "transforming
principle" that was somehow part of the dead III-S strain bacteria.
Today, we know that the "transforming principle" Griffith observed was the DNA of the III-S strain
bacteria. While the bacteria had been killed, the DNA had survived the heating process and was taken up
by the II-R strain bacteria. The III-S strain DNA contains the genes that form the protective polysaccharide
capsule. Equipped with this gene, the former II-R strain bacteria were now protected from the host's
immune system and could kill the host. The exact nature of the transforming principle (DNA) was verified
in the experiments done by Avery, McLeod and McCarty and by Hershey and Chase.
The Avery–MacLeod–McCarty experiment was an experimental demonstration, reported in 1944 by
Oswald Avery, Colin MacLeod, and Maclyn McCarty, that DNA is the substance that causes bacterial
transformation. It was the culmination of research in the 1930s and early 1940s at the Rockefeller
Institute for Medical Research to purify and characterize the "transforming principle" responsible for the
transformation phenomenon first described in Griffith's experiment of 1928: killed Streptococcus
pneumoniae of the virulent strain type III-S, when injected along with living but non-virulent type II-R
pneumococci, resulted in a deadly infection of type III-S pneumococci. In their paper "Studies on the
Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of
Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III", published in
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the February 1944 issue of the Journal of Experimental Medicine, Avery and his colleagues suggest that
DNA, rather than protein as widely believed at the time, may be the hereditary material of bacteria, and
could be analogous to genes and/or viruses in higher organisms.[
To show that it was DNA rather than some small amount of RNA, protein, or some other cell component
that was responsible for transformation, Avery and his colleagues used a number of biochemical tests.
They found that trypsin, chymotrypsin and ribonuclease (enzymes that break apart proteins or RNA) did
not affect it, but an enzyme preparation of "deoxyribonucleodepolymerase" (a crude preparation,
obtainable from a number of animal sources, that could break down DNA) destroyed the extract's
transforming power
Schematic Representation:
Two strains of bacteria - Rough (R) and Smooth (S)
o Rough - bacteria had a rough appearance in culture, non-virulent (doesn't kill)
o Smooth - bacteria had a smooth appearance in culture, virulent (kills)
Performed several experiments whose results can be summarized as follows:
o Mouse + Live S >> Died. Autopsy revealed infestation of S strain bacteria
o Mouse + Live R >> Lived a happy life
 These two experiments illustrate the effects of normal R and S strains
o Mouse + Heat-killed S >> Lived a happy life
o Mouse + Heat-killed R >> Lived a happy life
 These two experiments illustrate that dead bacteria by themselves are
harmless
o Mouse + Heat-killed S + Live R >> Died. Autopsy revealed infestation of S strain
o Apparently something from the heat-killed S changed the live R to make them virulent this was called transformation
 Griffith didn't know what it was that transformed the R strain into the S strain,
but he demonstrated that it could be done
Oswarld Avery, Maclyn McCarty, and Colin MacLeod (1944)
Performed the same experiment, only they used tissue cultures growing in petri dishes
o Heat-killed S + Live R + protease >> Live R and S colonies
o Heat-killed S + Live R + DNAse >> No growth
Other experiments - purified each chemical class associated with transformation and subjected
bacteria to each one individually
o Only DNA produced transformation
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Hershey and Chase conducted their experiments on the T2 phage, a virus whose structure had recently
been shown by electron microscopy.The phage consists of a protein shell containing its genetic material.
The phage infects a bacterium by attaching to its outer membrane and injecting its genetic material and
leaving its empty shell attached to the bacterium.
In their first set of experiments, Hershey and Chase labeled the DNA of phages with radioactive
Phosphorus-32 (the element phosphorus is present in DNA but not present in any of the 20 amino acids
from which proteins are made). They allowed the phages to infect E. coli, and through several elegant
experiments were able to observe the transfer of P32 labeled phage DNA into the cytoplasm of the
bacterium.
In their second set of experiments, they labeled the phages with radioactive Sulfur-35 (Sulfur is present
in the amino acids cysteine and methionine, but not in DNA). Following infection of E. coli they then
sheared the viral protein shells off of infected cells using a high-speed blender and separated the cells and
viral coats by using a centrifuge. After separation, the radioactive S35 tracer was observed in the protein
shells, but not in the infected bacteria, supporting the hypothesis that the genetic material which infects
the bacteria was DNA and not protein.
o
o
Bacteriophage - composed only of protein coat and DNA - injected something inside host
bacterial cell which contained its genetic information
Was the injected material DNA or protein?
87
In the first experiment, illustrated on the left, the "radioactive" substance was the protein coat. In
the second experiment, illustrated on the right, the "radiopactive" substance was the DNA. After
the bacteriophage had injected the genetic material into the cell, the solutions were
centrifuged and each reaction flask was measured for radioactivity.
In the first experiment, all of the radioactivity was in the fluid that the cells were originally
suspended.
In the second experiment, all of the radioactivity was in the bacteria.
It was concluded that since the radioactivity in the second experiment was in the bacteria, the
genetic information was contained in the DNA and not the protein.
88
What Are ESTs and How Are They Made?
An Expressed Sequence Tag is a tiny portion of an entire gene that can be used to help identify unknown
genes and to map their positions within a genome.
ESTs are small pieces of DNA sequence (usually 200 to 500 nucleotides long) that are generated by
sequencing either one or both ends of an expressed gene. The idea is to sequence bits of DNA that
represent genes expressed in certain cells, tissues, or organs from different organisms and use these "tags"
to fish a gene out of a portion of chromosomal DNA by matching base pairs. The challenge associated
with identifying genes from genomic sequences varies among organisms and is dependent upon genome
size as well as the presence or absence of introns, the intervening DNA sequences interrupting the protein
coding sequence of a gene.
An expressed sequence tag or EST is thus a short sub-sequence of a transcribed cDNA sequence. They
may be used to identify gene transcripts, and are instrumental in gene discovery and gene sequence
determination.[2] The identification of ESTs has proceeded rapidly, with approximately 65,9 million ESTs
now available in public databases (e.g. GenBank 18/6/2010, all species).
An EST is produced by one-shot sequencing of a cloned mRNA (i.e. sequencing several hundred base
pairs from an end of a cDNA clone taken from a cDNA library). The resulting sequence is a relatively low
quality fragment whose length is limited by current technology to approximately 500 to 800 nucleotides.
Because these clones consist of DNA that is complementary to mRNA, the ESTs represent portions of
expressed genes. They may be present in the database as either cDNA/mRNA sequence or as the reverse
complement of the mRNA, the template strand.
ESTs can be mapped to specific chromosome locations using physical mapping techniques, such as
radiation hybrid mapping, Happy mapping, or FISH. Alternatively, if the genome of the organism that
originated the EST has been sequenced one can align the EST sequence to that genome using a computer.
The current understanding of the human set of genes (as of 2006) includes the existence of thousands of
genes based solely on EST evidence. In this respect, ESTs have become a tool to refine the predicted
transcripts for those genes, which leads to the prediction of their protein products and ultimately their
function. Moreover, the situation in which those ESTs are obtained (tissue, organ, disease state - e.g.
cancer) gives information on the conditions in which the corresponding gene is acting. ESTs contain
enough information to permit the design of precise probes for DNA microarrays that then can be used to
determine the gene expression.
Full genome sequencing (FGS), also known as whole genome sequencing, complete genome
sequencing, or entire genome sequencing, laboratory process to determines complete DNA sequence genome at a single time. sequencing all of an organism's chromosomal DNA-including extrachromosomal
DNA as well as DNA contained in the mitochondria and for plants the chloroplast as well. Almost any
biological sample—even a very small amount of DNA or ancient DNA—can provide the genetic material
necessary for full genome sequencing. Such samples may include saliva, epithelial cells, bone marrow,
89
hair (as long as the hair contains a hair follicle), seeds, plant leaves, or anything else that has DNAcontaining cells. Because the sequence data that is produced can be quite large (for example, there are
approximately six billion base pairs in each human diploid genome), genomic data is stored electronically
and requires a large amount of computing power and storage capacity. Full genome sequencing would
have been nearly impossible before the advent of the microprocessor, computers, and the Information
Age.
Gene Expression:
The lac Operon in E. coli
Introduction
Gene expression is regulated in bacteria, causing genes to be turned on and off in response to environmental
signals. You will find information on how genes in bacteria are grouped together in functional groups called
operons, the functions of various segments of DNA in operons, how specific molecules start and stop transcription
within operons, and how certain molecules affect the rate of this transcription. Animations in the activity show
these processes.
The DNA of Escherichia coli is sufficient to encode about 4000 proteins, but only a fraction of these are
made at any one time. E. coli regulates the expression of many of its genes according to the food sources
that are available to it.
Gene Regulation in Bacteria
Bacteria adapt to changes in their surroundings by using regulatory proteins to turn groups of
genes on and off in response to various environmental signals.
An operon is a cluster of bacterial genes along with an adjacent promoter that controls t he
transcription of those genes.
When the genes in an operon are transcribed, a single mRNA is produced for all the genes in that operon.
This mRNA is said to be polycistronic because it carries the information for more than one type of protein.
The lac Operator
90
The operator is a short region of DNA that lies partially within the promoter and that
interacts with a regulatory protein that controls the transcription of the operon.
Here's an analogy. A promoter is like a doorknob, in that the promoters of many operons are similar.
An operator is like the keyhole in a doorknob, in that each door is locked by only a specific key,
which in this analogy is a specific regulatory protein.
The lac Regulatory Gene
The regulatory gene lacI produces an mRNA that produces a Lac repressor protein, which can
bind to the operator of the lac operon.
The general term for the product of a regulatory gene is a regulatory protein. The Lac regulatory
protein is called a repressor because it keeps RNA polymerase from transcribing the structural
genes. Thus the Lac repressor inhibits transcription of the lac operon.
The Lac Repressor Protein
In the absence of lactose, the Lac repressor binds to the operator and keeps RNA polymerase
from transcribing the lac genes.
91
Animate
It would be energetically wasteful for E. coli if the lac genes were expressed when lactose was not
present.
The effect of the Lac repressor on the lac genes is referred to as negative regulation.
The Effect of Lactose on the lac Operon
When lactose is present, the lac genes are expressed because allolactose binds to the Lac
repressor protein and keeps it from binding to the lac operator.
Allolactose is an isomer of lactose. Small amounts of allolactose are formed when lactose enters E. coli.
Allolactose binds to an allosteric site on the repressor protein causing a conformational change.
As a result of this change, the repressor can no longer bind to the operator region and falls off. RNA
polymerase can then bind to the promoter and transcribe the lac genes.
The lac Inducer: lactose
lactose is called an inducer because it turns on, or induces the expression of, the lac genes.
92
The presence of lactose (and thus allolactose) determines whether or not the Lac repressor is bound to
the operator.
Allolactose binds to an allosteric site on the repressor protein causing a conformational
change. As a result of this change, the repressor can no longer bind to the operator region
and falls off. RNA polymerase can then bind to the promoter and transcribe the lac genes.
Feedback Control of the lac Operon
When the enzymes encoded by the lac operon are produced, they break down lactose and
allolactose, eventually releasing the repressor to stop additional synthesis of lac mRNA.
Note
o
Adding a new substrate to the culture medium may induce the formation of
new enzymes capable of metabolizing that substrate.
The three enzymes are
a permease that transports lactose across the plasma membrane from the culture
medium into the interior of the cell
beta-galactosidase which converts lactose into the intermediate allolactose and
then hydrolyzes this into glucose and galactose. Once in the presence of lactose,
the quantity of beta-galactosidase in the cells rises from a tiny amount to almost
2% of the weight of the cell.
a transacetylase whose function is still uncertain.
93
The capacity to respond to the presence of lactose was always there. The genes for the three induced
enzymes are part of the genome of the cell. But until lactose was added to the culture medium, these
genes were not expressed (β-galactosidase was expressed weakly — just enough to convert lactose into
allolactose).
The most direct way to control the expression of a gene is to regulate its rate of transcription; that is, the
rate at which RNA polymerase transcribes the gene into molecules of messenger RNA (mRNA)
DNA Fingerprinting:
Repetitious DNA and DNA polymorphism: In eucaryotes, only a small portion of the genome
constitutes coding regions . In human only about 2% of the genome codes for protein, rest represents noncoding regions. The latter category includes the following types of repetitious DNAs.
a)
Simple Sequences-a short DNA sequence constitutes one unit and such a unit is repeated
tandemly
several
times.(e.g.
Satellite
DNA,Microsatellite/Short
Tandem
Repeats,Minisatellite/Variable Number Tandem Repeat)
b) Interspersed Repeats-they are scattered throughout the genome,however they do not form
any tandem repeats.
DNApolymorphism-It is this noncoding repeat sequences which are the basis for generation
of polymorphism among the individuals.The unit length as well as the number of repeats
varies from individual to individual,the total length of a specific sequence (say, one VNTR or
One STR) at differentclusters will be different in different individuals.
The DNApolymorphism involving non-coding simple sequenceDNA, is the genetic basis of
DNA fingerprinting.
DNAprofiles of no two individuals (except for identicaltwins) are identical
The Southern Blot is one way to analyze the genetic patterns which appear in a person's DNA.
Performing a Southern Blot involves:
1. Isolating the DNA in question from the rest of the cellular material in the nucleus. This can be done
either chemically, by using a detergent to wash the extra material from the DNA,or mechanically, by
applying a large amount of pressure in order to "squeeze out" the DNA.
2. Cutting the DNA into several pieces of different sizes. This is done using one or more restriction
enzymes.
3. Sorting the DNA pieces by size. The process by which the size separation, "size fractionation," is done
is called gel electrophoresis. The DNA is poured into a gel, such as agarose, and an electrical charge is
applied to the gel, with the positive charge at the bottom and the negative charge at the top. Because DNA
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has a slightly negative charge, the pieces of DNA will be attracted towards the bottom of the gel; the
smaller pieces, however, will be able to move more quickly and thus further towards the bottom than the
larger pieces. The different-sized pieces of DNA will therefore be separated by size, with the smaller
pieces towards the bottom and the larger pieces towards the top.
4. Denaturing the DNA, so that all of the DNA is rendered single-stranded. This can be done either by
heating or chemically treating the DNA in the gel.
5. Blotting the DNA. The gel with the size-fractionated DNA is applied to a sheet of nitrocellulose paper,
and then baked to permanently attach the DNA to the sheet. The Southern Blot is now ready to be
analyzed.
In order to analyze a Southern Blot, a radioactive genetic probe is used in a hybridization reaction with
the DNA in question. If an X-ray is taken of the Southern Blot after a radioactive probe has been allowed
to bond with the denatured DNA on the paper, only the areas where the radioactive probe binds [red] will
show up on the film. This allows researchers to identify, in a particular person's DNA, the occurrence and
frequency of the particular genetic pattern contained in the probe.
1. Hybridization is the coming together, or binding, of two genetic sequences. The binding occurs because
of the hydrogen bonds [pink] between base pairs. Between a A base and a T base, there are two hydrogen
bonds; between a C base and a G base, there are three hydrogen bonds.
2. When making use of hybridization in the laboratory, DNA must first be denatured, usually by using heat
or chemicals. Denaturing is a process by which the hydrogen bonds of the original double-stranded DNA
are broken, leaving a single strand of DNA whose bases are available for hydrogen bonding.
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3. Once the DNA has been denatured, a single-stranded radioactive probe [light blue] can be used to see if
the denatured DNA contains a sequence similar to that on the probe. The denatured DNA is put into a
plastic bag along with the probe and some saline liquid; the bag is then shaken to allow sloshing. If the
probe finds a fit, it will bind to the DNA.
4. The fit of the probe to the DNA does not have to be exact. Sequences of varying homology can stick to
the DNA even if the fit is poor; the poorer the fit, the fewer the hydrogen bonds between the probe [light
blue] and the denatured DNA. The ability of low-homology probes to still bind to DNA can be
manipulated through varying the temperature of the hybridization reaction environment, or by varying the
amount of salt in the sloshing mixture.
Every strand of DNA has pieces that contain genetic information which informs an organism's
development (exons) and pieces that, apparently, supply no relevant genetic information at all (introns).
Although the introns may seem useless, it has been found that they contain repeated sequences of base
pairs. These sequences, called Variable Number Tandem Repeats (VNTRs), can contain anywhere from
twenty to one hundred base pairs.
Every human being has some VNTRs. To determine if a person has a particular VNTR, a Southern Blot is
performed, and then the Southern Blot is probed, through a hybridization reaction, with a radioactive
version of the VNTR in question. The pattern which results from this process is what is often referred to as
a DNA fingerprint.
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A given person's VNTRs come from the genetic information donated by his or her parents; he or she could
have VNTRs inherited from his or her mother or father, or a combination, but never a VNTR either of his
or her parents do not have. Shown below are the VNTR patterns for Mrs. Banerjee [blue], Mr. Banerjee
[yellow], and their four children: D1 (the Banerjees' biological daughter), D2 (Mr. Banerjees‘ stepdaughter, child of Mrs. Banerjeeand her former husband [red]), S1 (the Banerjee' biological son), and S2
(the Banerjees' adopted son, not biologically related [his parents are light and dark green]).
Because VNTR patterns are inherited genetically, a given person's VNTR pattern is more or less unique.
The more VNTR probes used to analyze a person's
1. Paterniy and Maternity Because a person inherits his or her VNTRs from his or her parents,
VNTR patterns can be used to establish paternity and maternity. The patterns are so specific that a
parental VNTR pattern can be reconstructed even if only the children's VNTR patterns are known (the
more children produced, the more reliable the reconstruction). Parent-child VNTR pattern analysis has been
used to solve standard father- identification cases as well as more complicated cases of confirming legal
nationality and, in instances of adoption, biological parenthood.
2. Criminal dentification and Forensics DNA isolated from blood, hair, skin cells, or other genetic
evidence left at the scene of a crime can be compared, through VNTR patterns, with the DNA of a criminal
suspect to determine guilt or innocence. VNTR patterns are also useful in establishing the identity of a
homicide victim, either from DNA found as evidence or from the body itself.
3. Personal Identification The notion of using DNA fingerprints as a sort of genetic bar code to identify
individuals has been discussed, but this is not likely to happen anytime in the foreseeable future. The
technology required to isolate, keep on file, and then analyze millions of very specified VNTR patterns
is both expensive and
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impractical. Social security numbers, picture ID, and other more mundane methods are much more likely
to remain the prevalent ways to establish personal identification
Chapter 7 : Evolution
Evolution: The process that results inheritable changes in a population spread over many generations
(change in allele frequencies over time). Biological evolution refers to populations and not to individuals
and that the changes must be passed on to the next generations. Genes mutate, individuals are selected, and
populations evolve.
Evidences of evolution
From comparative anatomy
Homologous organs
Analogous organs
Same basic structural plan and origin but
different function
Different structure and origin but same
function
It suggests common ancestry
It do not suggests common ancestry
Indicates Divergent evolution
Indicates Convergent evolution
Thorn of Bougainvillea &
Thorn of citrus and spine of Opuntia
Tendril of Cucurbits
Tendril of cucumbers and tendril of pea
Flipper of seal, wing of bat, cats paw, human
hand
Wing of insect and wing of bird
Vestigial organs: Functionless homologous organs that have no apparent function in certain organism.(
supposed to be remnants of organs that had been well developed and functional in their ancestors but had
became modified during evolution)
E.g.
1. Vermiform appendix in man
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2. Pelvic girdle in python
3. Nictitating membrane
4. Coccyx or tail vertebrae in man
Divergent evolution
Origin of a variety of species from a common
ancestral form
Divergent evolution is the process of two or
more related species becoming more and more
dissimilar.
Convergent evolution
Independent development of similar forms and
features by unrelated organisms to adapt to a
similar environment
Unrelated species become more and more
similar in appearance as they adapt to the same
kind of environment
As they adapted to different environments, the
appearance of the two species diverged
Homologous organs supports it
Divergent
Analogous organs supports it
Evolution
, the evolutionary pattern in which two species gradually become increasingly different. This type of
evolution often occurs when closely related species diversify to new habitats. On a large scale, divergent
evolution is responsible for the creation of the current diversity of life on earth from the first living cells.
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On a smaller scale, it is responsible for the evolution of humans and apes from a common primate
ancestor.
Adaptive radiation is one example of divergent evolution
Convergent Evolution
Convergent evolution takes place when species of different ancestry begin to share analogous traits
because of a shared environment or other selection pressure. For example, whales and fish have some
similar characteristics since both had to evolve methods of moving through the same medium: water.
Parallel Evolution
Parallel evolution occurs when two species evolve independently of each other, maintaining the same level
of similarity. Parallel evolution usually occurs between unrelated species that do not occupy the same or
similar niches in a given habitat.
Stabilizing selection favors the norm, the common, average traits in a population In nature, natural
selection is most commonly stabilizing. The average members of the population, with intermediate body
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sizes, have higher fitness than the extremes. Natural selection now acts against change in form, and keeps
the population constant through time.
Directional selection favours those individuals who have extreme variations in traits within a
population. Natural selection may be directional: it may favour, for example, smaller individuals and
will, if the
character is inherited, produce a decrease in average body size. Directional selection could, of course, also
produce an evolutionary increase in body size if larger individuals had higher fitness.
Disruptive selection, like directional selection, favours the extreme traits in a population. Disruptive
selection differs in that sudden changes in the environment creates a sudden forces favoring that extreme
Natural selection can sometimes favour extremes over the intermediate types. This is called
disruptive selection.
In nature, sexual dimorphism is probably a common example
Directional selection has been studied using artificial selection experiments. Natural selection can also be
stabilizing or disruptive.
Genetic Drift changes populations…..
Random change in allele frequency causes an allele to become common
Founder Effect:
A cause of genetic drift attributable to colonization by a limited number of individuals from a
parent population
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When few individuals colonize a new habitat, genetic drift will more than likely occur.
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The founding population is small and again the alleles present in this small population will not be
representative of the original population.
Saltation (from Latin, saltus, "leap") is a sudden change from one generation to the next, that is large, or
very large, in comparison with the usual variation of an organism. The term is used for occasionally
hypothesized, nongradual changes (especially single-step speciation) that are atypical of, or violate,
standard concepts involved in neo-Darwinian evolution. The unorthodox emphasis on saltation as a means
of evolutionary change is called saltationism.
Gene Flow:
Genetic exchange due to the migration of fertile individuals or gametes between populations (reduces
differ ences between populations)
Natur al Selecti on:
Differ ential success in reproduction; only for m of microevolution that adapts a population to its
environment
A
B
C
An example of adaptive radiation –
these species all diverged from a
common ancestor (founder species)
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FOUNDER SPECIES
Adaptive radiation: The diversification, over evolutionary time, of a species or group of species into
several different species or subspecies that are typically adapted to different ecological niches (for
example, Darwin's finches).
Adaptive radiation is one example of divergent evolution
.
Artificial selection: The process by which humans breed animals and cultivate crops to ensure that future
generations have specific desirable characteristics.
(In artificial selection, breeder’s select the most desirable variants in a plant or animal population and
selectively breed them with other desirable individuals).
Big bang theory: The theory that states that the universe began in a state of compression to infinite
density, and that in one instant all matter and energy began expanding and have continued expanding ever
since.
Disruptive selection: Selection favoring forms that deviate in either direction from the population
average. Selection favours forms that are larger or smaller than average, but works against the
average forms between the extremes.
Genetic drift: Changes in the frequencies of alleles in a population that occur by chance, rather than
because of natural selection.
Gene flow: The movement of genes into or through a population by interbreeding or by migration.
Gene frequency: The frequency in the population of a particular gene relative to other genes at its locus,
expressed as a proportion (between 0 and 1) or percentage (between 0 and 100 percent).
Gene pool: All the genes in a population at a particular time.
Hardy-Weinberg principle: In population genetics, the idea that if a population experienced
no selection,
no mutation,
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no migration,
no genetic drift, and
random mating,
then the frequency of each allele and the frequencies of genotype in the population would remain the same
(constant) from one generation to the next.
p2 + 2pq + q2 = 1
(p + q)2 = 1
Calculation of allele frequencies
Recessive traits: If the frequency of a recessive trait such as cystic fibrosis or PKU is known, it is
possible to calculate allele frequencies and genotype frequencies using the Hardy Weinberg equation
and its
assumptions as follows:
i. Say 1 in 1, 2500 Indian newborns have cystic fibrosis which means that the frequency of
homozygotes for this recessive trait is
q² = 1/2,500 = 0.0004
ii. The square root of the frequency of recessives is equal to the allele frequency of the cystic
fibrosis allele
q = (0.0004)0.5 = 0.02
iii. The frequency of the normal allele is equal to 1 - the frequency of the cystic fibrosis allele
p = 1- q = 1 - 0.02 = 0.98
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iv. The frequency of carriers (heterozygotes) for the cystic fibrosis allele is
2pq = 2 (0.98)(0.02) = 0.04 or 1/25
v. The frequency of homozygotes for the normal allele is
p² = (0.98)² = 0.96
vi. Thus the population is composed of three genotypes at the calculated frequencies of
homozygous normal = 0.96
heterozygous carriers = 0.04
homozygous affected = 0.0004
Bottleneck effect- The size of a population becomes drastically reduced by natural disasters ( i.e. volcanic
eruptions, earthquakes, fires) will kill individuals non-selectively.
The small population left will not be a correct representation of the original population.
Some alleles may be over-represented and others under- represented.
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Chronology of Human Evolution:
Time period
10-15 Mya
2 Mya
Name
Brain
capacity
Remarks
Dryopithecus (ape like)
East Africa Asia ;
closely related to
Chimpanzee
Ramapithecus (man like)
Shivalik hills;Erect
posture , small canine
teeth
Australopithecines ( cave
dwellers)
500cc
African ape man; height
1.5 meter
Homo habilis
650-800cc
Tool maker, community
life
1.5 Mya
Homo eractus (Java ape man)
900cc
Knew to use fire, larger
teeth,
100,000-40,000
years ago
Neanderthal man
1450cc
East and central asia
25000yrs ago
Homo sapiens
1650cc
Modern man ; height 1.5
to1.8 meters;f lat face
(Million years ago= Mya)
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Chapter – 8 HUMAN HEALTH AND DISEASE
Definition of health
Health is a state of complete physical,mental and social well-being.
Types of diseases
Infectious – easily transmitted from one person to another .
.Non- infectious - not transmitted from diseased persons to others.
.
Common infectious diseases in humans
- V iral diseases-common cold, aids,polio,chicken pox,measles
- Bacterial diseases -pneumonia,typhoid,cholera
- Fungal diseases - ringworms
- Helminthic diseases- ascriasis, filariasis
Protozoal diseases -malaria, amoebiasis
Name of disease
Causal organism
Symptoms
Transmission
Common cold
Rhino virus
Nasal congestion &discharge,sore
throat,cough,headache for 3 to 7
days
By droplet infection
Through Air
Pneumonia
Bacteria- Streptococcus
pneumoniae
Alveoli get filled with
fluid,problem in respiration,fever,
chill, cough.
By inhaling
droplets/aerosols
released byinfected
persons,sharing
utensil.
Malaria
Protozoa- Plasmodium vivax
Chill, high fever recurring every
3-4 days.due to rupture of
RBC.Haemozoin released in
blood
By female
Anopheles mosquito
bite.
Filaria
Helminthic worm- Wuchereria
bancrofti,W. malayi
Chronic inflammation 0f
organs,specially lower
limbs,genital organs affeected
By bite of female
culex mosquito
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Rringworms
Microsporum,Trichophyton,Epider
mo phyton.
Dry scaly lesions on
skin,scalp,nail. Intense itching.
LIFE CYCLE OF Plasmodium
108
From soil,by using
clothes, towels,comb
of infected person.
STAGES IN THE LIFE-CYCLE OF Plasmodium
IMMUNITY – The overall ability of host to fight with disease causing organism is called immunity.
The immune system – The system of our body which protects us from various infectious agents and
cancer.
IMMUNITY
INNATE
ACQUIRED
Non specific type, present at time of
An individual acquires it during his life
life.
Birth.
Charcteristic features:
Types: a)Physical barrier - skin
b)Physiological barrier – saliva ,
tear, acid in stomach.
c)Celluar barrier - PMNL
neutrophil,macrophages,
monocytes.(d) Cytokine - Interferons
1)Specificity
2)Diversity
3)Discrimination between self and non
self
Cells involved in acquired immunity
Lymphocytes- the major cells of the immune system.
They are of 2 types: B lymphocytes ,produced & matured in bone marrow.
T lymphocytes, produced at bone marrow but matured in thymus
B-cells produce antibodies in response to pathogen in blood.
Antibody reacts with antigen(pathogen) & destroys it.
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This is called humoral immune response as the antibodies are found in the blood
Some activated B cells remain as memory cells.
110
Structure of an antibody consisting of 2 heavy & 2 light polypeptide chains.
T
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T-CELLS act differently.
They produce a clone of T cells in resonse to pathogen.
Helper T cells stimulate B cells & killer T cells to destroy non-self cells.
Killer T cells directly attack foreign cells.
This type of immune response is known as CELL MEDIATED IMMUNITY (CMI)
TYPES OF ACQUIRED IMMUNITY :
ACTIVE IMMUNITY
PASSIVE IMMUNITY
Antibody produced within own
body.
Antibodies transferred from
another individual.
It is long lasting.
Not long lasting.
Takes time to produce
Provides immediate relief.
Vaccination and Immunization
Vaccination refers to the administration of any vaccine.
Immunization is the process by which the body produces antibodies in response to the vaccine to fight
infections.
Vaccine is a preparation of antigenic proteins of pathogens or inactivated/weakened pathogen. It is
introduced into the body to generate antibodies which can neutralize the pathogens during actual
infection. Vaccines also generate memory B & T cells that recognize the pathogens quickly.
Vaccines that contain performed antibodies produce quick immune response and provide Passive
Immunity e.g. vaccines against tetanus & snakebite.
Other vaccines provide Active Immunity e.g. oral polio vaccine, BCG,cholera vaccine.
Allergies
The exaggerated response/hypersensitiveness of the immune system of a person to certain antigens
coming in contact with or entering into the body is called allergy.
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Substances that cause allergy are called ALLERGENS.
Common allergens:
Dust,pollen,spores,feather,fur,cosmetics, some food substances,heat,cold,sunlight etc.
Symptoms of allergy:
Sneezing, running nose, watery eyes, difficulty in breathing, itching etc.
Drugs to reduce symptoms of allergy:
Antihistamines, adrenalin and steroids.
Auto-immunity
It isa condition when structural & functional damage is caused due to the attack of the self cells of the
body by its own immune cells . Examples : Rheumatoid arthritis, Insulin- dependent diabetes.
Immune system of the body
1. Primary Lymphoid organs where B &T lymphocytes mature and acquire their antigen specificity
e.g.bone marrow and thymus.
2. Secondary lymphoid organs where B & T lymphocytes migrate after maturation and undergo
proliferation and differentiation e.g. spleen, lymph nodes, tonsils, Peyer’s patches of small
intestine, appendix.
See diagram in page154 of NCERT TEXT BOOK.
MALT – Mucosal Associated Lymphoid Tissue located within lining of respiratory, digestive and urogenital
tracts & forms about 50% lymphoid tissue in human body.
AIDS(ACQUIRED IMMUNO DEFICIENCY SYNDROME)
-
Caused by HIV( HUMAN IMMUNO DEFICIENCY VIRUS),a retrovirus.
This virus has RNA as its genetic material.
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Replication of retrovirus
113
Transmission of HIV infection
i)sexual contact with infected person
ii) transfusion of contaminated blood & blood products.
iii)by sharing infected needles.
iv)from infected mother to her child.
Detection
a)ELISA(enzyme linked immuno sorbent assay)
b)PCR(polymerase chain reaction)
c)RIP ( radio immunoprecipitation assay)
d)Western blot (cofirmatory test)
Prevention
i)use of sterile needle, surgical instruments, syringes
ii)protected sex
iii)counseling before & after the test
iv)NACO(National AIDS Control Organisation) has started a number of programmes.
Cancer
Cancer arises from the mutation of a nor ma l gene.
Mutated genes that cause cancer are called oncogenes.
It is thought that several mutations need to occur to give rise to cancer
Cells that are old or not functioning proper ly nor mally self destruct (degenerate) and are replaced by
new cells.
However, cancerous cells do not self destruct and continue to divide rapidly producing millions of new
cancerous cells.
 Cell division becomes uncontrolled in ca ncer ous cells.
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Carcinogens
Ionising radiation – X Rays, UV light
Chemicals – Tar from cigarettes
Virus infection –Papilloma virus can be responsible for cervical cancer.
Hereditary predisposition – Some fa milies are more susceptible to getting certain cancers. Remember
you can’t inherit cancer its just that you maybe mor e susceptible to getting it.
Benign & malignant tumours
Benign tumours do not spread from their site of origin, but can crowd out (squash) surrounding cells eg
brain tumour, warts.
Malignant tumours can spread from the original site and cause secondary tumours. This is called
metastasis.
Cancer detection and diagnosis
Detection is based on Biopsy & Histopathological studies of the tissue & blood for increased cell count.
In biopsy a thin section of suspected tissue is stained & examined under microscope.
Early detection is essential.
Radiography, CT, MRI are very useful to detect cancer of internal organs.
Cancer Treatment
1-Local therapy:
surgery.
radiation therapy.
2-Systemic treatment:
chemotherapy.
Hor monal therapy.
Monoclonal antibodies.
3-Supportive care.
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4 -Administration of biological response modifier
- Interferon given to activate immune system &
help in destroying tumour.
Drugs of abuse
1)Opoids : e.g. heroin ,codein, morphene obtained from Papaver somniferum,a depressant
2)Cannabinoids: e.g. hashish,marijuana, charas , ganja. Obtained from Cannabis sativa.
effects on cardiovascular system.
These have
3)Coca alkaloid or Cocaine , obtained from Erythroxylum coca.It interferes with transport of
neurotransmitter dopamine
Causes of drug and alcohol abuse:
1)Curiosity, 2) Need for adventur e, 3)Peer pressure, 4)Excitement, 5) Experimentation, 6) To escape from
stress, 7) Unsupportive fa mily structure,8)Repeated use of drugs 7 alcohol.
Dependence and addiction to drugs & alcohol leads the patient to (aa) ignor e all social nor ms (,b)
social adjustment problems,(c) withdrawl symptoms and (d
d) the person may need medical
supervision.
Warning signs of drug & alcohol abuse
1)Drop in academic performance, 2)Absence from school/college, 3)Lack of inter est, 4)Withdrawl,
5)Isolation, 6)Depr ession & fatigue, 7)Aggr essive & rebellious behaviour, 8)Loss of interest in hobbies,
9)Behavioural change, 10)Change in eating & sleeping habits, 11)Stealing, 12)Loss of weight etc.
Prevention and control of drug and alcohol abuse:
Avoid undue peer pressure
Educating & counselling the child to face problems of life, stresses and to accept failures &
disappointments of life
Seeking help from parents, teachers,peers & elders to vent their feelings of anxiety,stress & guilt
Looking for da nger signals
Seeking professional & medical help for deaddiction.
Some important definitions:
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Substance abuse –– It is the use of illicit drugs or the abuse of prescription or over-thecounter drugs for purposes other than those for which they are indicated or in a manner or
in quantities other than directed.
Physical dependence –– It denotes a state when the body of the abuser requires the continuous presence of
the drug within it.
Psychological dependence –– When this develops, the substance abuser becomes mentally hooked to the
drug & has a continuous uncontrollable craving for it.
Some substances that are commonly abused are:
Cannabinoids e.g. hashish and marijuana
Stimulants e.g.tobacco, nicotine, cocaine, ampheta mines
Depr essants e.g. alcohol, barbiturates
Narcotics e.g. opioids, morphine derivatives as heroin, opium
Hallucinogens e.g. LSD, mescaline
Other compounds e.g. steroids, inhalants
Probable questions & answers from Human Health and Diseases
Very short answer type question (1 mark)
1. What is disease?
Ans. Disease is the condition when the functioning of one or more organ(s) or system(s) of the body
is/are adversely affected and characterized by various symptoms.
2. Name one infectious and one non-infectious disease, which are the major causes of
mortality?
Ans. - Infectious disease
- AIDS or Hepatitis-B;
- Non-infectious disease – Cancer.
3. What are pathogens?
Ans. Pathogens are those organisms which cause disease .
4. Name two diseases that spread by droplet infection.
Ans. Pneumonia and common cold spread by droplet infection.
5. What name is given to infectious stage of Plasmodium?
Ans. Sporozoites.
6. Give the scientific name of pathogen causing malignant malaria in humans.
Ans. Plasmodium falciparum.
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7. What causes swelling of the lower limbs in patients suffering from filariasis?
Ans. The filarial worms live on the lymphatic vessels of the lower limbs, where they
cause inflammation; that causes swelling of lower limbs.
8. What are interferon’s?
Ans. Interferon‘s are the proteins produced by virus-infected cells in our body.
As.
9. Name the two kinds of acquired immunity.
Active immunity and passive immunity are the two limbs of acquired immunity.
10. Name the kind of cells responsible for rejecting organ transplants.
Ans. T-lymphocytes are responsible for rejecting organ transplants.
1) Why do children of metro cities of India suffer from allergies and asthma? 2
2) A doctor injects preformed antibodies against a snake bite. What type of
immunity does it develop in the patient? 1
3) A person has developed allergic reactions like sneezing, watery eyes, running
nose and difficulty in breathing. What could be the reason for these symptoms?
How can it be controlled? 2
4) A patient has lost his immunity. 3
(i) Name the disease associated with it.
(ii) Name the confirmatory test to diagnose the disease.
(iii) Why did he lose his immunity?
5) A person claimed that he has seen sounds, heard colours and smelt light. 3
(i) What could be the possible reason?
(ii) Name two chemicals responsible for this condition.
(iii) Mention any one source for these chemicals.
Short answer type question (2 marks)
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1. Fill in the blanks in the different columns of the table given below :
Disease
Causative
Mode of
Symptoms
organism
transfer
Filariasis
Wuchereria
a
Lymphatic vessels
of lower limbs affected.
b
Trichophyton
Common
c
cold
Ascariasis
Ascaris
Using towels of
Dry, scaly lesions
infected persons
on body.
Droplets from
Affect nose and
sneezing of
Respiratory passage;
infected persons
Sore throat.
Through contaminated
d
water, vegetables and
fruits
Ans.
(a) Bite of Culex mosquito.
(b) Ringworm
(c) Rhino virus
(d) Blockage of intestinal passage, anemia, muscular pain.
2. How do saliva and tear help to prevent bacterial infection?
Ans. -Saliva and tear contain lysozymes.
-Lysozymes are the enzymes which digest the cell wall of bacteria.
-By lysing the cell wall, they kill the bacteria and prevent their infection.
3. What is vaccination? How does it help producing immunity?
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Ans.
Vaccination is the process of introducing a preparation of antigenic proteins of the pathogens or
weakened or killed pathogen into the body.
-The vaccines induce quick multiplication of B and T-lymphocytes; some of them are stored as
memory cells.
-The B-lymphocytes quickly produce antibodies, which neutralize the antigen during infection.
4. Mention the symptoms of AIDS.
Ans. The symptoms of AIDS include:
(i) Swollen lymph nodes
(ii) night sweats
(iii) loss of body weight
(iv) fever
(v) infection by pathogens of other diseases.
5. Write the full form of ELISA. Give an example of the clinical application of ELISA.
Ans. -Enzyme Linked Immuno Sorbent Assay.
-ELISA test is used in the diagnosis of AIDS, hepatitis-B and other STDs.
6. List four reasons to justify the ban on intake of cannabinoids by sports persons.
Ans. (i) Cannabinoids affect the cardiovascular system.
(ii)They cause addiction and when the regular dose is not taken, there are unpleasant withdrawal
symptoms, which may be life-threatening.
(iii)The person shows reckless behaviour, vandalism and violence.
(iv)Excess dose can lead to coma and death due to heart failure, cerebral hemorrhage, etc.
Short answer type questions (3 marks)
1. What are the advantages of people being healthy?
Ans. When people are healthy,
(i) They are efficient at work which consequently increases productivity and brings economic
prosperity.
(ii) Health increases longevity.
(iii) It reduces infant and maternal mortality.
2. Name the two major/broad categories of diseases and differentiate between them.
Ans. The two major/broad categories of diseases are:
(i) Infectious diseases and
(ii) Non-infectious diseases.
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Differences:
Infectious Diseases
Non-infectious Diseases
- These are the diseases which are
- These are the diseases which are not
easily transmitted from one
transmitted from one person to the
person to another.
other.
- They are caused by biological
3.
- They occur due to deficiencies,
agents, called pathogens.
habits, hereditary factors, etc.
e.g. Diphtheria.
e.g. Cancer.
(a) Name the respective forms in which the malarial parasite gains entry into
(i) Human body and
(ii) Body of female Anopheles.
(b)Name the hosts where the sexual and the asexual reproductions of
malarial parasite occur respectively.
(c) Name the toxin responsible for the appearance of symptoms of malaria in humans. Why
do these symptoms occur periodically?
Ans.
(a) (i) Sporozoite
(ii) Gametocyte
(b) - Sexual reproduction in mosquito.
- Asexual reproduction in human body.
(c) Haemozoin
- Haemozoin is released when the RBCs rupture and release the pathogen.
- Some cells of pathogen enter fresh RBCs and reproduce asexually and repeat
the cycle; hence the symptoms appear periodically.
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4. Define innate immunity. Name and explain the category of barrier which involves
macrophages.
Ans. Innate immunity refers to all those defence element with which a person is born and are always
available to protect the body.
-Macrophanges form part of the cellular barrier.
-The cellular barrier includes the following specialized cells;
(i) Polymorphonuclear leucocytes.
(ii) Monocytes.
(iii) Natural killer lymphocytes and
(iv) Macrophages.
-
these cells phagocytose and destroy the invading microbes.
5. What is meant by writing H2L2 for an antibody? Name any four types of antibodies
produced in our/human body?
Ans. - Each antibody molecule has four peptide chains.
- Of them, two are small and called light chains (L) and two of them are longer
and called heavy chains (H); hence written as H2L2.
The four types of antibodies are IgA, IgE, IgG and IgM.
6. Differences between innate and acquired immunity and give examples of each.
Ans. Differences:
Innate Immunity
Acquired Immunity
- Innate immunity consists of all
- The immunity which is acquired after
the defence elements with which
birth, is called acquired immunity.
an individual is born.
- It consists of specified cells-
- It consists of various types of
barriers that prevent the entry of
B-lymphocytes, T-lymphocytes and
foreign agents.
antibodies circulating in the body fluids.
- e.g. development of immunity by
- e.g. Lysozymes, mucus-coated
vaccination or by contracting the disease.
epithelium.
7. Enumerate the steps taken by WHO to control AIDS.
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Ans.
The steps taken by WHO include:
(i) Ensuring use of disposable needles and syringes.
(ii) Checking of blood samples for HIV.
(iii) Free distribution of condoms.
(iv) Advocating safe sex.
(v) Controlling drug abuse.
(vi) Promoting regular check up for HIV in susceptible cases.
8. How do normal cells get transformed into cancerous neoplastic cells? Mention the
differences between viral oncogenes and cellular oncogenes.
Ans. The transformation of normal cells into cancerous neoplastic cells is induced by
physical, chemical and biological agents collectively called carcinogens. They lose
the property of contact inhibition.
Difference:
Viral Oncogenes
Cellular Oncogenes
- These are the genes present in the
- These are the genes present in normal
oncogenic viruses, which effect
cells and code for growth factors;
oncogenic transformation of the
when activated under certain conditions,
cells they infect.
can cause oncogenic transformation of the cell.
9. What is meant by withdrawal syndrome? What are its characteristic features?
Ans. Withdrawal syndrome refers to the characteristic and unpleasant manifestation of
the body, when regular dose of drugs/alcohol is abruptly discontinued.
Characteristic features:
(i) Anxiety
(ii) Excess sweating
(iii) Shakiness
(iv) Nausea
(v) In some cases it may be severe and life-threatening.
Long answer type questions (5 marks)
1. What are carcinogens? Describe the different types of them.
Ans. Carcinogens are those physical, chemical or biological agents which transform the
normal cells into cancerous/neoplastic cells.
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Types of carcinogens:
(i) Physical Agents:
- Ionizing radiations like X-rays, gamma rays and
- Non-ionizing radiation like UV; these cause damage to DNA leading to
neoplastic transformation.
(ii) Chemical carcinogens:
- Asbestos, cigarette smoke, etc. are carcinogens for lung cancer.
(iii) Oncogenic viruses, which possess viral oncogens that transform the normal
cells into neoplastic cells.
2. (i) Explain metastasis. Why is it fatal?
(ii) The lymphocytes are of two types B and T-cells. Why are they called so?
(iii) A person has injured on a road accident and required an urgent immune
response.
Ans.
(a) What did the doctor immediately do to this patient?
(b) What kind of an immunity was he providing to this patient?
(c) Define this type of immunity?
(i) Metastasis is the property of tumor cells, which get separated from a tumor,
spread to different sites in the body through body fluids and produce
secondary tumors wherever they are lodged. Since secondary tumors are
formed at several parts of the body, it is difficult to be diagnosed and treated;
hence it is fatal.
(ii) Those lymphocytes which undergo maturation in the bone marrow are called
B-cells while those which undergo maturation in the thymus are called
T-cells.
(iii) (a) The doctor would inject preformed antibodies.
(b) It provides passive immunity.
(c) Passive immunity is defined as the immunity developed by directly taking
the preformed antibodies that were developed in other vertebrates.
3. (a) Represent schematically the lifecycle of HIV.
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(b) What are the various routes by which transmission of human
immunodeficiency virus takes place?
Ans.
(a)
(b) The various routes of transmission of human immunodeficiency virus
includes:
(i) sexual contact with the infected person.
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(ii) by transfusion of contaminated blood and blood products.
(iii) from infected mother to the child through the placenta.
(iv) through contaminated needles and syringes.
Chapter-9 strategies for enhancement in food production
Animal Breeding-objectives:
1.Improved growth rate.
2.Increased production.
3. Improve Desirable Qualities.
4. Improved resistance.
Methods: i).Inbreeding:-Breeding between same breed for 4-6 generations.Ex-cows,baffaloes,poultry
In breeding depression- continued in breeding reduces fertility even productivity
A single outcross often helps to overcome inbreeding depression
ii) Outbreeding- breeding between unrelated animals
It is of two types – 1. Out crossing- mating within the same breed but not having
ancestors.
2.) Crossbreeding- superior males of one breed are mated with superior females of another breed to get
better progency.e.g.- cows of inferior breed with superior bull.
3) Hisardale- is a new breed of sheep developed in Punjab by crossing Bikaneri Eves and Marano Rams.
4) Interspecific hybridization- male and female animals of two different species are mated. E.g.- mule is
crossbreed of male donkey and female horse.
5) Control breeding- it is done by artificial insemination and multiple ovulation embryo transfer
technology (MOET)
(a) Artificial insemination- semen of superior male is collected and injected unto the reproductive tract
of selected female.
The spread of certain diseases can be controlled by this method.
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(b) MOET- This is a technique for herd improvement. Hormones(FSH) are given to the cow for
inducing follicular maturation and super ovulation.The cow is either mated with best bull or
inseminated .It is done in cattle,sheep,rabbits etc.
Steps in Plant breeding:-1 Collection of variability-Collection and preservation of all different wild
varieties,species,relatives of cultivated species etc. are also called
germplasm collection.
2.Evaluation and selection of parents-Germplasm is evaluated to identify plants with desirable traits.
3.Cross hybridization among the selected parents-Two plants having two desired characters are
hybridized to get new hybrid having two desired characters.
4.Selection and testing of superior recombinants-Selection of the plants having desired character
combinations.
5.Testing,release and commercialization of new cultivars-Newly selected lines are evaluated for their
yield,agronomic traits,disease resistance etc.and released into the market
Green revolution -Crop production.
White revolution -Milk production
Blue revolution -Fish production
Biofortification-Breeding crops with higher levels of vitamins and minerals
SCP (Single cell protein )-Microbes such as bacteria,yeast,algae are treated in various ways and used as
food. Eg-spirulina can be grown in waste water(from potato processing plant)
Tissue culture- cultured part called explant.
Types -1.Meristem –When apical part is taken and cultured.
Uses:
a)Rapid clonal multiplication
b)Production of virus free plants
c)Production of transgenic plants
d)Germplasm collection
2. Protoplast culture and somatic hybridization- The plant cell laking cell wall is protoplast. Fusion of
protoplast is done by Polyethylene glycol. Pomato is somatic hybrid of potato and tomato.
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Micropropagation-Tissue culture technique used for rapid vegetative propagation of ornamental plants
and fruit trees.
Somaclone-Plants obtained from single plants by vegetative propagation.
1 Mark questions
Q1.Name two techniques involved in controlled breeding experiments.
Ans-a) Artificial insemination(AI)
b)Multiple ovulation embryo transfer technology(MOET)
Q2.What is blue and green revolution?
Ans- Blue-Increased fish production
Green-Crop
Q3 What is inbreeding depression?
Ans-Loss of vigour due to increase in homozygosity in recessive alleles.
Q4. What is heterosis or hybrid vigour?
Ans-Phenotypic superiority over either of its parents.
Q5.Name the Indian variety of rice patented by an American company.
Ans-Basmati.
Q6.What is Pomato?
Ans-Somatic hybrid of tomato and potato.
Q7 Name the algae used as protein rich food.
Ans-Spirulina
Q8.Expand-MOET and SCP.
Ans-MOET-Multiple ovulation embryo transfer technology.
SCP-Single cell protein.
Q9.What is quarantine?
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Ans-Careful examination of all introductions for the presence of insects,disease causing organisms.
Q10.What is cultivar?
Ans-All cultivated varieties of plants.
Q1. What is Biofortification?
Ans-Breeding crops with higher levels of vitamins and minerals, higher proteins and lesser fats.
Objectives of improving-a) Protein content and quality.
b)Oil content and quality.
c)Vitamins.
d)Micronutrient and mineral content.
Q2.Which part of the plant is best suited for making virus free plants?
Ans-a) Apical and auxillary meristems
b) These are free from virus due to absence of vascular tissues.
Q3.What is breed? What are the objectives of animal breeding?
Ans- a) Group of animals related by descent,similar in appearance,shape and size
b) Improved growth rate , increased production of milk, meat, egg, wool, silk etc.
Q4.Define out-crossing? Suggest an advantage.
Ans-a) Practice of mating of animals within the same breed,but no common ancestors on either side upto
4-6 generations.
b) A single out-cross often helps to overcome inbreeding depression.
Q5.What is artificial insemination?what is its importance?
Ans_a)Collection of semen from the male bull and injected into the female cow.
b)Help to overcome several normal mating problems.
Q6. What are the differences between aqua and pisciculture?
Ans-a) Production of aquatic plants and animals like fishes , prawns ,lobsters, crabs etc.
b) Pisciculture is the production of fishes only.
Q7. What is animal husbandry?
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Ans-Breeding and rearing of livestock like buffaloes ,cows ,pigs, horses , cattle etc.Extended, it includes
poultry farming and fisheries also.
Q8. What is bird flu?
Ans- Contagious disease of animals caused by viruses that only infect birds .
symptoms : fever ,cough and sore throat.
Q9. Name the most common species of honey bees of India?what are the products from the honey bees?
Ans_Apis indica.
b) Honey , bee wax and bee venom.
Q10. What is germplasm?How it is maintained?
Ans-a)Some total of alleles of genes.
b)Low temp.in the form of seeds, Plant tissue culture.
3 Marks Questions
Q1.What does inbreeding mean? Suggest its advantages. What is the danger of inbreeding?
Ans-a)Mating of more closely related individual within same breed
b)i)Development of pure line
ii)increases homozygosity
iii) Elemination of harmful recessive genes
iv)Accumulation of superior genes
c) Inbreeding depression-Reduction of fertility and productivity.
Q2.Name the methods employed in animal breeding. Which method is the best? Why?
Ans-a) Natural methods-these includes inbreeding and out breeding
b) Artificial method – MOET. It includes super ovulation and embrayo transplantation .
Artificial insemination – produces good quality progeny , economic .
Q3. Explain the procedure of MOET technique in cattle.
Ans: FSH is injected to induce follicular maturation and super ovulation .
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06 to 08 eggs are produced.
Cow is inseminated artificially . fertilized eggs transferred to surrogate mother.
Q4. What is interspecific hybridization ?Give one example of crop in which it practiced and mention
one advantage.
Ans : Crossing individuals of two different species to produce a hybrid.
Ex- Rice variety ADT –37 from oryza japonica and oryza indica
Advantage : Brings useful genetic variations of two or more lines together.
Q5. What is cross-breeding ? what advantages does it have? Give example.
Ans: Mating between different breeds. Superior male of one and superior female of another breed.
Desirable qualities of two breeds are combined
Example : Hisardale – breed of sheep from Bikaneri ews Merino rams .
5 Marks Questions
Q1. Explain the points that have to be considered for successful bee- keeping?
Ans : a) Knowledge of nature and habits of bees.
b) Selection of suitable location .
c) Catching and hiving of swarms.
d) Management of bees – hives.
e) Handling and collection of honey and bee- wax
Q2. Write the scientific name of sugarcane grown in north and south India respectively. Mention their
characteristic features. Mention the characteristic of the hybrid produced by crossing these two varieties .
Ans: (i) North – Saccharum barberi – poor yield , poor sugar content
South – Saccharum officinarum – thicker stem , higher yield and higher sugar content.
(ii) High yield , thick stems , higher sugar content , ability to grow in both North and South India.
Q 3. Describe various steps involved in plant breeding .
Ans : (i) Collection of variability – collection and preservation of all the different wild varieties , species (
germplasm collection )
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ii) Evaluation and selection of parents – germplasm is evaluated to identify plants with desirable
combination of characters .
iii) Cross hybridisation among the selected parents- to bring two good qualities in a hybrid , cross
hybridization is done.
iv) Selection of testing of superior Recombinants - the superior recombinants are selected and tested .
v) Testing , release and comercialisation of new cultivars - newly selected lines are evaluated for yield
,other agronomic traits, disease resistance etc.
Chapter – 10: Microbes in Human Welfare
Microbes: Present everywhere. E.g.



 Thermal vents of geyser (Temp. above 1000c)
 Deep in soil.
 Under snow.
Diverse. Protozoa, Bacteria, Fungi, Virus, Viroids, Prione (Proteinacious infectious agents)
Useful : Antibiotics.
Harmful: cause diseases.
In Household Products:





Everyday : Lactobacillus (LAB) Lactic acid Bacteria – form curd from milk.
 Increase Vit . B12
 Check disease causing microbes in our stomach.
Fermentation of dough for dosa, idli (CO2 produced)
Making bread – bakers yeast. Saccharomyces cerevisiae.
Toddy making from sap plam.
Cheese making (eg. Swiss chesse by Propionibacterium Sharmanii, Roquefort cheese by fungi.)
In Industrial Products :

Beverages and antibiotics.
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
Fermentors : Large vessels for growing microbes.
Fermented Beverages :

Beverages like wine, bear, whisky, Brandy, Rum (Saccharomyces cerevisiae)
Malted cereals and fruit juices used to produce ethanol, wine and beer produced without
distillation; Whisky, brandy, rum produced after distillation.
Antibiotics : (Against life)


Penicillin produced by Alexander Fleming from Penicillium notatum while working with
Staphylococci Earnest Chain and Howard Plorey awarded Nobel Prize in 1945 for establishing
Penicillin as an effective antibiotic.
Uses : Treat diseases like plague, whooping cough, diphtheria, leprosy.
Chemicals: Engymes and other Bioactivities Molecules:
Uses:









Aspergillus niger for production of Citric Acid.
A cetobacter aceli for production of Acetic Acid.
Clostridium butylicum for production of Butynic Acid.
Lactobacillus for production of Lactic acid.
Lipases used in detergents to remove oil strains from Laundry.
Pectinases and Proteases to clarify bottled jucies.
Streprokinase (from Streptococcus) as clot buster in patiento with myocardial infraction (heart
attack).
Cyclosporin A – as inmunosuppresant in organ transplant patients (produced by Trichoderma
polysporum)
Statins produced by yeast Monascus purpureus used as blood, cholesterol lowering agent.
Microbes in sewage Treatment:




Major comporent of waste water, human excreta.
Waste water sewage.
Cannot be disposed directly into rivers and streams.
Before disposal sewage treated in sewage treatment plants (STPs)
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




Treatment done in two stages.

Primary :
Physical removal of particles large and small by filtration and
sedimentation.
:
Solids – primary sludge.
 Supernatant – effluent.

Secoundry: Primary effluent taken to large aeration tanks.
 Agitated mechanically and air pumped into it.
 Aerobic microbes form masses with fungal filaments flocs.
 Microbes consume organic matter in effluent for growth.
 BOD ( Biological oxygen demand) reduced.
 Passed into settling tank.
 Bacterial flocs sedimented (activated sludge)
 Small part of activated sludge used as inoculums in aeration tank.
 Major part pumped into large anaerobic sludge digesters.
 Anaerobic bacteria digest bacteria and fungi.
 Bacteria produce gases such as menthane, hydrogen sulphide and CO2 –
Biogas.
Secondary effluent released into rivers and streams.
No man made technology available till date.
Untreated sewage if released into rivers causes pollution.
Ministry of environment and Forests iniated Ganga Action Plan and Yamuna Action
Plan.
Biogas plant:





Concrete tank 10- 15 mts deep, & slurry or dung fed.
Floating cover placed above rises as biogas content rivers.
Connecting pipe for supply of biogas.
Used for cooking and lighting.
Development by
IARI :- Indian Agriculture Research institute
&
KVIC:- Khadi and village Industries Commission.
Microbes as Biocontrol Agents :

Insecticides and Pesticides toxic, harmful & are pollutearts.

Natural predation better method.

No of pests kept in check, not totally eradicated.

Food chains not disturbed

Eg. Ladybird and Dragon flies useful to get rid of aphids and mosquitoes.
Bacillin thureingiensis (Bt) used to control butterfly caterpillar.

Mode
of spores operation.

o Available is sachets, mixed with water and sprayed on plants.
o Eaten by insect larva
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





o Toxin released in gut – larvae Rpilled.
Now Bt toxin genes introduced into plants – resistant to insect pests.
e.g. Bt cotton.
Tungus Trichoderma now being developed.
Nucleoply hadrovires – good for narrow spectrum insecticide applications.
Advantage :No negative impacts on plants, mammals, birds, fish or target insects.
For overall IMP (Intergrated pest Management) programme.
For ecologically sensitive areas.
AS Biofertilizers:




Chemical fertilizers major pollutant.
Switch to organic farming and use of biofertilizers need of the time.
Main sources of biofertilizers. Bacteria, Fungi & Cyanobacteria.
Eg Rhizobium present in roots of leguminious plants fix atmospheric nitrogen into usable organic
form.
Azospirillium and Azatobacter – free living bacteria – fix atmosphere Nitrogen.
Symbiotic Associations
Eg Glomus sp. form myeorrhiza

Fungal symbiont absorbs phosphorus from soil and passes it to plant.

Plants show
 resistance to root – borne pathogers.
Tolerance to salinity and drought
Increase in growth and development.

Cynobacteria – autotrophic – fix atmospheric nitrogen

Imp biofertilizer.
e.g. Anabaena, Nostoc, Oscillatoria.

Blue green algae – increase fertility by adding organic matter.

No of biofertilizers commercially available.
Process of sewage treatment in STP
Primary treatment(physical )
Filtration &sedimentation
Secondary treatment(biological)
Effluent loaded in large aeration tank
Agitation & rapid growth of aerobic microbes
(flocs)
Consumes organic matter ,reduces BOD
Effluent passed to settling tank
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Flocs sediments form – activated sludge
Poured into sludge digester(small amount of a.s.
Very short answer type (1 mark)

Name two vitamins produced by microbial fermentation.
Vitamin B12 & vitamin B2

What is the botanical name of baker‘s yeast?
Saccharomyces cerevisieae

Q. Milk starts to coagulate when lactic acid bacteria is added to warm milk as a starter. Mention
two benefits LAB provides?
A. i) Besides coagulation, improves nutritional quality by increasing vitaminB12
ii) Check disease causing microbes in our stomach.
Short answer type question(2 marks)

State the use of:

Trichoderma with respect to organ transplant

Nucleo polyhedrovirses with respect to pest management
Ans: Trichoderma polysporum produces a bioactive molecule cyclosporin A Used as an
immunosuppresive agents in organ transplant
Nucleo polyhedrovirses, a baculovirus attack many insects and arthopods, but do not harm plant,
mammals, fish etc.

Why should be sewage treated before its disposal?
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Sewage cantains faecal matter & many pathogenic microbes which would pollute water and cause
water borne diseaMention one commercial use of lipase.
It is helpful in removing oily stains from the laundry.
Statins acts as competetive inhibitor of enzyme responsible for synthesis of cholestrerol

What is primary sludge?
All the solids that settledown during primary treatment

Name the pests, lady birds and dragonflies help to get the rid of respectively
Ladybi rds-aphids, dragonflies-mosquitoes.
Microbes can be used to lessen the burden of use of chemicals and pesticides-Explin how this can
be achieved?
Use of friendly microbes which kills & stop the growth. Reduce dependency of chemicals of
bacteria- Bacillus thuringenesis, used to kill bollworm catterpillars on cotton

Give the role of microbes in single cell protein.
SCP is protein rich microbial biomass which can be used as food and feed. SCP has all essential
amino acid, fat content is low. Spirulina has become an important food supplement

What is micorhiza? How does it help as biofertilizers?
Association between roots of higher plants and fungus
Solubilize phosphorus and produce growth promoting substances
It protects plants from soil pathogens

What is BOD? What does it mean if water samples has more BOD?
Biochemical oxygen demands. It represent the amount of dissolved oxygen that would be
consumed if all the organic matter in one litter of water is oxidized by microbes
More value of BOD means the water sample is polluted by organic matter.

Name any two cyanobacteria. How do they serve as main source biofertizer.
Nostoc & anabaena. They possess heterocyst and fix atmospheric nitrogen into ammonia. Fixed
form of nitrogen leaches out in soil & is absorbed by higher plants

What is the difference between Bt and Bt cotton? Explain the use of Bt as a biological
control.
137
Bt stands for bacteria name –Bacillus thuringenesis whose gene has been incorporated in cotton
plant to make Bt cotton. Bt is mixed with water & sprayed, It is eaten by insect larvae, in the gut
toxin is released and insect is killed

Name the blank spaces a, b, c, d in the table given belowTypes of microbes
Bacterium
b
c
Name
a
Aspergillus niger
d
Commercial product
Clot buster enzyme
Citric acid
Butyric acid
a, Steptococcus: b, Fungus: c, Bacterium: d, Clostridium butylicum

Give reason- a) Bottled fruit juices brought from market are clearer as compared to those made at
home, b)Large holes are found in swiss-cheese, c) The insect which are so called pest are not
eradicated in organic fumes.
a) Clarified by the use of pectinases and proteses, b) large holes due to production of large amount
of carbon di oxide by bacterium Propionibacterium sharmanii, c) insect pest are not eradicated
because the beneficial predatory insect and other parasites which depend upon them as food or
host would not be able to survive

Name the gobar gas liberated from biogas plant. which type of bacteria are responsible for its
production? Give advantage.
It is methane gas. By the activity of methanogenic bacteria

Advantage: it is readily combustible, it do not pollute environment
Q. Short answer type question(3 marks)
Differentiate between a) primary sludge and activated sludge, b) biofertilizer and chemical fertilizer, c)
primary sewage treatment and secondary sewage treatement.
Primary sludge
Activated sludge
All solids that settle down during primary
treatment
The sediment formed during secondary
treatment
Biofertilizer
Chemical fertilizer
There are micro-organism which enrich
their nutrient quality of the soil
There are the chemicals synthesized in
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factories and give only specific nutrient
Primary sewage treatment
Secondary sewage treatment
It involves the physical removal of
particles by filtration and sedimentation
Pretreated effluent is biologically treated
with microbes in aeration tank.
Q. Draw labelled diagram of a bacteriophage


Q. Label the parts numbering 5 ,3 ,9 , 1 of a typical biogas plant.
Give the role of spent slurry.
Constituent of biogas
5) floating gas holder, 3) sludge, 9) digester, 1) Dung and water
139
Spent slurry is used as fertilizer,
Constituent of biogas is CH4+CO2+H2
Long answer type question(5 marks)

Answer briefly:

1) How is sewage harmful to men?

2) What is organic farming?

3)which group of organisms attack insect and arthopod? How are they best biocontrol biological
agent,

4) What is the difference between flocks and primary sludge?
 Sewage is municipal waste water which contains human excreta, other waste and pathogenic
microbes
 The natural method of pest and pathogen control involving use of viruses, bacteria and other
insect i.e. which are the natural predator and pest
 Baculovirus :

species specific ,narrow- spectrum ,eco-friendly insecticides.
 Flocks
masses of bacteria with
form mesh

Primary-Sludge
sands, silt, small pebbles settledown
during primary treatment.
fungal filament which
like structure.
Write short notes on: a) bakers yeast, b) alcohol c) statin d)Brewers yeast e) streptokinase
Probable Questions.
MICROBES IN HUMAN WELFARE
140
Q1 what are biofertilizers ? give 1 example.
Q.2 Name the bacteria used in the production of "Swiss Cheese"
Q.3 What is the scientific name for Brewer's yeast?
Q.4 Name a bioactive molecule used as an immuno suppressive agent.
Q.5 Why are bottled fruit juices appear clearer than the home made ones.
Q.6 Three water samples labelled A, B & C has BOD values 20mg/L, 8mg/L and 400 mg/L respectively.
Which sample of water is most polluted and which one most clean.
Hint : The greater the BOD of waste water, more is its polluting potential.
Q7) Name the group of bacteria that are capable to live in high temperatures above 100 C
Q8) To which class of fungi does Penicillium belong? (1)
Q9_ Which of the steps are related to Nitrogen fixation? (1)
a) N2 NH3
b) N2 NO3
c) N2 Amino acid
d) Both a and b
Q10) Which of the following organisms has Nif Gene? (1)
a) Penicillum b) Rhizobium c) Aspergillus . d) Streptococcus
2 Marks Questions
Q.1 What are statins? What is its significance?
Q.2 In which food will you find LAB? Mention its two useful applications.
Q.3 can microbes be used to decrease the use of chemical fertilizers and pesticides? Explain how?
What is BOD? What does it indicates
.
3 Marks Questions
Q.1 Draw a labelled diagram of a typical biogas plant.
Q.2 Explain Why :
(a) Cow dung is used in the generation of biogas.
(b) A small amount of curd is added in fresh milk to convert it into curd.
(c) Baculovirus are used in narrow spectrum insecticidal application.
Q.3 What are antibiotics? Give two examples. What is their significance?
Give one example and one use of the following (3)
a) Free living fungi
b) Symbiotic fungi
c) Free living bacteria
Q4) How is it that the Cry protein produced by Bacillus thuringiensis (Bt) does harm the bacteria but only
killsthe insect larvae?
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Q5) Differentiate Antibodies and antibiotics
Q6) How are biofertilizers different from fertilizers such as NPK that we buy in the market? Justify the
role of Rhizobium as a biofertilizer.
5 Marks Questions
Q1)Explain how microbes are used in sewage treatment?
Q2)What do you understand by integrated pest management (IPM)? Explain with example and state its
importance
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Chapter-11: BIOTECHNOLOGY: PRINCIPLES AND PROCESSES
Biotechnology is a broad area of science involving multiple disciplines designed to use living
organisms or their products to perform valuable industrial or manufacturing processes or
applications pertaining to human benefit.
Recombinant DNA technology:
An organism's genome contains virtually all the information necessary for its growth and
development
Determining the molecular sequence of DNA that makes up the genome of different organisms is an
international scientific goal, several laboratories are participating worldwide in this task. It is thought that
having access to the complete DNA sequence of an organism can help us not only to decipher its biology
but also help us understand major biological questions, for instance, what makes one species pathogenic
whereas a related species is not.
Each cell (with a few exceptions) carries a copy of the DNA sequences which make up the
organism's genome. However, many genomes are large and complex (for instance the human
genome is made up of ~3000 x 106 base pairs). A particular DNA sequence (for instance the
allele of a gene) can be very small in comparison. And it probably occurs only once or twice
within the genome (ie only one or two copies per cell). This means that a particular DNA
sequence will be present as only a (very) small part within the complex mixture of DNA
sequences that make up the genomic DNA of that organism.
It is often necessary to 'break up' large DNA molecules into smaller, more manageable fragments
- often to sizes ranging from 100 bp to 2 kb (bear in mind that each resulting DNA fragment is an
individual molecule). These smaller fragments can then be manipulated more easily - to isolate
particular DNA fragments, to characterise their molecular sequence, to determine their function,
to determine their position in relation to other sequences within the genome, to use them to
express proteins, etc. .
Progress in understanding genetic mechanisms at the molecular level was slow. Then came
the discovery of various bacterial and viral enzymes which modify and synthesise nucleic acids
(DNA and RNA), along with the means to produce more out with the organism from which they
were originally isolated. The application of these enzymes for manipulating DNA (no matter what
the source) led to the creation of Recombinant DNA Technology which has enabled great
scientific advances in the field of biology, has created new scientific disciplines and has
revolutionised our world.
Recombinant DNA Technology
Techniques for
- Isolation
- Digestion
- Fractionation
- Purification of the TARGET fragment
- Cloning into vectors
- Transformation of host cell and selection
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- Replication
- Analysis
- Expression of DNA
Restriction enzymes
. Restriction enzymes are endonucleases
Bacterial enzymes
Different bacterial strains express different restriction enzymes
The names of restriction enzymes are derived from the name of the bacterial strain they
are isolated from
Cut (hydrolyse) DNA into defined and reproducible fragments
Basic tools of gene cloning
Names of restriction endonucleases
Titles of restriction enzymes are derived from the first letter of the genus +
the first two letters of the species of organism from which they were isolated.
EcoRI - from Escherichia coli
BamHI - from Bacillus amyloliquefaciens
HindIII - from Haemophilus influenzae
PstI - from Providencia stuartii
Sau3AI - from Staphylococcus aureus
AvaI - from Anabaena variabilis
Enzymes that can cut (hydrolyse) DNA duplex at specific sites. Current DNA technology is
totally dependent on restriction enzymesThe EcoRI restriction enzyme--the first restriction
enzyme isolated from E. Coli bacteria--is able to recognize the base sequence 5' GAATTC 3'.
Restriction enzymes cut each strand of DNA between the G and the A in this sequence. This
leaves "sticky ends" or single stranded overhangs of DNA. Each single stranded overhang has the
sequence 5" AATT 3'. These overhanging ends will bond to a fragment of DNA which has the
complementary sequence of bases
Restriction enzymes recognise a specific short nucleotide sequence
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This is known as a Restriction Site
The phosphodiester bond is cleaved between specific bases, one on each DNA strand
The product of each reaction is two double stranded DNA fragments
Restriction enzymes do not discriminate between DNA from different organisms
Most restriction enzymes will cut DNA which contains their recognition sequence, no matter the
source of the DNA
Restriction endonucleases are a natural part of the bacterial defence system
Part of the restriction/modification system found in many bacteria
These enzymes RESTRICT the ability of foreign DNA (such as bacteriophage DNA) to
infect/invade the host bacterial cell by cutting it up (degrading it)
The host DNA is MODIFIED by METHYLATION of the sequences these enzymes
recognise
o Methyl groups are added to C or A nucleotides in order to protect the bacterial
host DNA from degradation by its own enzymes
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Hundreds of restriction enzymes have been isolated and characterised
Enables DNA to be cut into discrete, manageable fragments
Type II enzymes(II Recognise a specific target sequence in DNA, and then break the
DNA (both strands), within or close to, the recognition site) e.g. EcoRI, these are those
used in the vast majority of molecular biology techniques .
Many Type II restriction endonucleases recognise PALINDROMIC sequences (From Greek
palindromos, running back again, recurring : palin, again)
A segment of double-stranded DNA in which the nucleotide sequence of one strand reads
same in reverse order to that of the complementary strand. (always read from the same
direction)
For example, EcoRI recognises the sequence
5'-G A A T T C-3'
3'-C T T A A G-5'
Different enzymes cut at different positions and can create single stranded ends ('sticky
ends') with overhangs
Some generate 5' overhangs - eg: EcoRI
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Some generate 3' overhangs - eg: PstI
Some generate blunt ends- eg: SmaI
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The 'sticky' overhangs are known as COHESIVE ENDS
The single stranded termini (or ends) can base pair (ANNEAL) with any complementary
single stranded termini
This is the basis for RECOMBINANT DNA TECHNOLOGY
Inserting foreign DNA into a cloning vector
Restriction enzymes are a useful tool for analysing Recombinant DNA
After ligating a particular DNA sequence into a cloning vector, it is necessary to check that the
correct fragment has been taken up. Sometimes it is also necessary to ensure that the foreign
DNA sequence is in a certain orientation relative to sequences present in the cloning vector.
Checking the size of the insert
Checking the orientation of the insert
Determining pattern of restriction sites within insert DNA
DNA fractionation
Separation of DNA fragments in order to isolate and analyse DNA cut by restriction enzymes
Electrophoresis
Electrophoresis is a technique used to separate and sometimes purify macromolecules especially proteins and nucleic acids - that differ in size, charge or conformation. As such, it
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is one of the most widely-used techniques in biochemistry and molecular biology
Linear DNA fragments of different sizes are resolved according to their size through gels made of
polymeric materials such as polyacrylamide and agarose. For instance, agarose is a
polysaccharide derived from seaweed - and gels formed from between 0.5% to 2% (mass/volume
i.e. 0.5 to 2.0g agarose/100 ml of aqueous buffer) can be used to separate (resolve) most sizes of
DNA When charged molecules are placed in an electric field, they migrate toward either the
positive or negative pole according to their charge. In contrast to proteins, which can have
either a net positive or net negative charge, nucleic acids have a consistent negative charge
imparted by their phosphate backbone, and migrate toward the anode
DNA is electrophoresed through the agarose gel from the cathode (negative) to the anode
(positive) when a voltage is applied, due to the net negative charge carried on DNA
When the DNA has been electrophoresed, the gel is stained in a solution containing the chemical
ethidium bromide. Ethidium bromide is a fluorescent dye that intercalates between bases of
nucleic acids and allows very convenient detection of DNA fragments in gels, This compound
binds tightly to DNA (DNA chelator) and fluoresces strongly under UV light - allowing the
visualisation and detection of the DNA. Like any molecule that binds to DNA, Ethidium
bromide is hazardous. It is a carcinogen. Finally,, the separated DNAs are cut out from the gel
and extracted from the gel piece(elution).
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Fig:Seperation of DNA fragments according to size.
Recombinant DNA technology:
DNA cloning is the isolation of a fragment or fragments of DNA from an organism and placing in
a VECTOR that replicates independent of chromosomal DNA. The RECOMBINANT DNA is
propagated in a host organism, the resulting CLONES are a set of genetically identical organisms
which contain the recombinant DNA
Why is DNA cloning important?
DNA cloning is involved in a number of applications (GENETIC ENGINEERING). Many
techniques for DNA isolation and manipulation have been worked out and are now routinely
followed in scientific laboratories.
Three main purposes for cloning DNA
1) DNA sequencing
Determining the sequence of the bases in the DNA can tell us about which proteins or RNAs are
encoded and their sequences, which sequences control their expression (GENE PROMOTERS
and other control sequences), as well as any possible mutations which might alter their function.
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Having access to the complete DNA sequence of an organism can help us decipher the biology of
that organism.
2) Protein production
Isolating the gene which encodes a desired protein (haemoglobin, interferon) may allow that gene
to be over-expressed so that the protein can be produced in bulk for study or use
3) Engineering animals/plants/proteins
The ability to alter the properties of proteins as well as create genetically modified animals and
plants (TRANSGENICS) has lead to their use for research and for therapeutic and commercial
purposes. The technology may lead to the development of new therapies for the treatment of
disease (GENE THERAPY).
Cloning and Expression Vectors
Isolated DNA is cloned into VECTORS for long term storage, propagation of the DNA and for
production of protein from gene(s) encoded in the DNA
What are cloning vectors?
Cloning vectors are extra-chromosomal 'replicons' of DNA which can be isolated and can
replicate independently of the chromosome. Vectors usually contain a selectable marker - a gene
that allows selection of cells carrying the vector e.g. by conferring resistance to a toxin. DNA of
interest can be cloned into the vector and replicated in host cells, usually one which has been well
characterised.
Commonly used vector systems
Bacterial plasmids
Bacteriophages
Cosmids
Yeast artificial chromosomes (YACs)
Ti plasmid (plants)
Eukaryotic viruses such as baculovirus (insect cells), SV40 virus and retroviruses.
Characteristics of a Cloning Vector
Origin of replication (ORI)
This process marks autonomous replication in vector. ORI is a specific sequence of nucleotide in DNA
from where replication starts. When foreign DNA is linked to this sequence then along with vector
replication, foreign (desirable) DNA also starts replicating within host cell.
Selectable Marker
Besides ORI, a cloning vector should have selectable marker gene. This gene permits the selection of host
cells which bear recombinant DNA (called transformants) from those which do not bear rDNA (nontransformants).
Charecteristics of Selectable marker:
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A gene whose expression allows one to identify cells that have been transforrned or transfected with
a vector containing the marker gene.
A marker gene is used to determine if a piece of DNA has been successfully inserted into the host
organism.. A gene, usually encoding resistance to an antibiotic, added to a vector construct to allow easy
selection of cells that contain the construct from the large majority of cells that do not. Gene that allows
for selection of cells carrying the gene. More commonly, selectable markers provide resistance against
cytotoxic insults .A selectable marker will protect the organism from a selective agent that would
normally kill it or prevent its growth. In most applications, only one in a several billion cells will take up
DNA. Rather than checking every single cell, scientists use a selective agent to kill all cells that do not
contain the foreign DNA, leaving only the desired ones .Antibiotics are the most common selective
agents. In bacteria, antibiotics are used almost exclusively.
Restriction sites
It should have restriction sites, to allow cleavage of specific sequence by specific Restriction
Endonuclease. Restriction sites in E.coli cloning vector pBR322 include HindIII , EcoRI , BamHI , SalI,
PvuI, PstI, ClaI etc.
A Cloning Vector that Works with Plant Cells
The most commonly used plant cloning vector is the "Ti" plasmid, or tumor-inducing plasmid. This
plasmid is found in cells of the bacterium known as Agrobacterium tumefaciens, which normally lives in
soil. The bacterium has the ability to infect plants and cause a crown gall, or tumorous lump, to form at
the site of infection. The tumor-inducing capacity of this bacterium results from the presence of the Ti
plasmid. The Ti plasmid itself, a large, circular, double-stranded DNA molecule, can replicate
independently of the A. tumefaciens genome. When these bacteria infect a plant cell, a 30,000 base-pair
segment of the Ti plasmid - called T DNA - separates from the plasmid and incorporates into the host cell
genome. This aspect of Ti plasmid function has made it useful as a plant cloning vector (natural
geneticengineer).
The Ti plasmid can be used to shuttle exogenous genes into host plant cells. This type of gene transfer
requires two steps: 1) the endogenous, tumor-causing genes of the T DNA must be inactivated and, 2)
foreign genes must be inserted into the same region of the Ti plasmid. The resulting recombinant plasmid,
carrying up to approximately 40,000 base pairs of inserted DNA and including the appropriate plant
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regulatory sequences, can then be placed back into the A. tumefaciens cell. That cell can be introduced
into plant cell protoplasts either by the process of infection or by direct insertion.
Once in the protoplast, the foreign DNA, consisting of both T DNA and the inserted gene, incorporates
into the host plant genome. The engineered protoplast - containing the recombinant T DNA - regenerates
into a whole plant, each cell of which contains the inserted gene. Once a plant incorporates the T DNA
with its inserted gene, it passes it on to future generations of the plant with a normal pattern of Mendelian
inheritance.
Plasmids are the most commonly used vector system. Several types are available for cloning of
foreign DNA in the host organism Escherichia coli. Many E. coli plasmids allow the expression
of proteins encoded by the cloned DNA
Bacteriophage are another common vector system used for cloning DNA. These are viruses
which 'infect' E. coli. The M13 bacteriophage is a single-stranded DNA virus which replicates in
E. coli in a double-stranded form that can be manipulated like a plasmid. It can be used to
produce single-stranded DNA copies which are useful for DNA sequencing.
Strategy for cloning DNA into a plasmid (or other cloning) vector
SUBCLONING
cut DNA of interest with the appropriate restriction endonuclease(s)
separate fragments by gel electrophoresis
purify target fragment from gel
ligate fragment with a plasmid cut with the same restriction endonuclease(s) - ligation is
performed using the enzyme DNAligase, ATP and Mg2+ ions
Transformation is the process by which plasmids (or other DNA) can be introduced into a cell. For
E. coli transformation with plasmids is quite straightforward, plasmids can be introduced by
electroporation or by incubation in the presence of divalent cations (usually Ca2+) and a brief heat
shock (42°C) which induces the E. coli cells to take up the foreign DNA
There are different methods to select for transformed cells. For instance, transformants can be
selected as antibiotic-resistant colonies on agar plates containing antibiotic.
For E. coli transformed with plasmids, colonies grown on antibiotic-containing plates should all
carry plasmids. However, this does not guarantee that the plasmid contains an insert. It is possible
that the vector has re-ligated and not incorporated an insert.
A means to determine which clones contain plasmids with inserts is to use a positive control
method such as insertional inactivation. This provides a clear way of recognising recombinants
from those carrying re-ligated vector. The following two methods are most commonly used
1. antibiotic selection and replica plating
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2. colour selection: blue/white selection using the lacz gene
Insertional inactivation Subcloning a DNA fragment into an active gene (usually a marker gene whose function can be easily
detected) will disrupt the function of that gene. This can be detected by looking for colonies that no
longer display that phenotype.
Colour selection
A more common method to determine which transformants contain plasmids with inserts is to use colour
selection. For E. coli, this involves the lac complex and blue/white screening.
The lac complex is comprised of the LacI gene and the lacZ gene. The gene lacZ produces the enzyme
beta-galactosidase, which can break down a derivative of lactose called X-gal (5-bromo-4-chloro-3indolyl-beta-D-galactopyranoside). This produces a blue dye, which colours the colony blue. In E. coli,
the expression of the lacZ gene is regulated by the LacI repressor protein (product of the LacI gene)
which binds to the promoter, and prevents transcription until another lactose analogue is added. IPTG
(isopropyl-beta-D-thiogalactopyranoside) is a non-degradable lactose analogue which binds to the LacI
repressor protein and displaces it from DNA it binds in the lac promoter system. Transcription of lacZ can
then occur and X-gal can be broken down.
Usually, modern cloning vectors encode a shortened derivative of lacZ (lacZ'), which encodes the Nterminal alpha-peptide of beta-galactosidase. A strain of E. coli is used which produces only the Cterminal portion of the enzyme, the transformant can use the reconstituted enzyme to break down X-gal.
The polylinker site in these vectors is located within the lacZ' gene.
Cloning an insert into this site will disrupt the gene and recombinants will be unable to break down X-gal.
Colonies carrying plasmid with no insert will be coloured blue whereas colonies carrying recombinant
plasmid will be white.
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For plasmids such as pBR322, which contains two antibiotic resistance genes, cloning an insert into one
of these will disrupt that gene and inactivate the resistance to that antibiotic.
For example, if DNA is cloned into the BamHI site in the Tetr gene, then transformed bacteria should be
plate onto media containing the other antibiotic (ampicillin). Positive clones can then be selected by
replica plating.
Colonies are transferred by replica plating on to identical positions on two more plates, each of which
contains one of the antibiotics which the parental plasmid confers resistance to - in this case tetracycline
and ampicillin. Transformants which carry plasmids with insert should be unable to grow on the
tetracycline plate and can be selected from the identical position on the ampicillin plate on which they
should still be able to grow.
Analysis of clones
One of the first steps is to identify clones carrying the recombinant plasmid, with the desired
DNA insert. This can be done by 'picking' clones - choosing individual bacterial colonies in order
to isolate the plasmid DNA from each of them. Single bacterial colonies are grown in culture
broth containing the selection antibiotic in order to maintain the plasmid. The plasmid DNA is
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extracted by the standard minipreparation technique and then analysed by restriction digest. After
digesting the DNA, different sized fragments are separated by agarose gel electrophoresis and the
sizes determined by comparison with known DNA molecular weight markers.
1.
PCR(Polymerase Chain Reaction):
The polymerase chain reaction (or PCR) is a technique for the in vitro amplification of a desired
sequence of DNA. PCR allows the generation of a large quantity of DNA product (up to several
g) from only a few starting copies. It has been shown that PCR can be used to generate a
detectable quantity of DNA from only one starting target (or template) molecule.
PCR was developed in the mid-1980's, but has already found multiple applications, such as:
1. Rapid amplification of intact genes or gene fragments
2. Generation of large amounts of DNA for sequencing
3. Generation of probes specific for uncloned genes by selective amplification of a specific
segment of cDNA
4. Analysis of mutations for medical applications
5. Detection of minute amounts of DNA for forensic purposes
6. Amplification of chromosomal regions adjacent to genes of known sequence and many
more·
Development of PCR won the Nobel prize for Kary Mullis and co-workers.
PCR principle
The PCR reaction is a DNA synthesis reaction that depends on the extension of primers
annealed to opposite strands of a dsDNA template that has been denatured (melted apart) at
temperatures near boiling. By repeating the melting, annealing and extension steps, several
copies of the original template DNA can be generated.
The amount of starting material (target) needed is very small
It is not necessary to isolate the desired sequence, because it will be defined by the primers that
are used in the reaction. The primers are oligonucleotides complementary to different regions
on the 2 strands of DNA template (flanking the region to be amplified).
The primer acts as a starting point for DNA synthesis. The oligo is extended from its 3' end by
DNA polymerase.
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157
Primer design
PCR is a cycle of three steps:
1. DENATURATION - the strands of the DNA are melted apart by heating to 95°C
2. ANNEALING - the temperature is reduced to ~ 55°C to allow the primers to anneal to
the target DNA
3. POLYMERISATION/EXTENSION - the temperature is changed to the optimum
temperature in order for the DNA polymerase to catalyse extension of the primers, i.e. to
copy the DNA between the primers.
The cycle is repeated over and over again - as many times as needed to produce a detectable
amount of product.
Typical cycling regime
Approximately 20-40 cycles of the 3 reaction steps are performed in a PCR reaction. A typical
reaction sequence would be:
Initial denaturation - 95°C for 2 mins
30 cycles of
95°C (30 seconds denaturation)
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55°C (30 seconds primer annealing)
72°C (60 seconds primer extension,
for fragments up to 1 kb)
Final extension of all DNA ends - 72°C for 10 mins
Storage of DNA - 4°C
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Discovery of a thermostable DNA polymerase
The breakthrough came with the discovery of the thermostable DNA polymerase Taq
polymerase, from the thermophilic bacterium, Thermus aquaticus, which lives in hot
springs., Taq polymerase enzyme can resist the high temperatures required to melt the
template DNA apart without denaturation (loss of activity) and works best at high
temperatures (72°C). This led to improved specificity & sensitivity. Annealing of primers to
sites other than the target sequence is significantly reduced at the higher temperatures used
for Taq polymerase.
The fact that only one aliquot ot Taq polymerase needs to be added to the PCR reaction
means that all components can be added to the tube at the start of the reaction - allowing
the automation of the PCR. Heating blocks which can be programmed to carry out the time
and temperature cycles for a PCR have been developed (thermal cycler machine).
Applications of PCR
1) Cloning a gene encoding a known protein
2) Amplifying 'old DNA'
3) Amplifying cloned DNA from vectors
Convenient way of checking the inserts - amplified DNA can be analysed by electrophoresis,
Southern blotting
4) Creating mutations in cloned genes
5) Rapid amplification of cDNA ends - RACE
.
6) Detecting bacterial or viral infection
* AIDs infection
* Tuberculosis (Mycobacterium tuberculosis)
7) Cancer
Detecting mutations that occur in cancer and monitoring cancer therapy. Determining if a patient
is free of malignant cells
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8) Genetic diagnosis
a. Diagnosing inherited disorders
* Cystic fibrosis
* Muscular dystrophy
* Haemophilia A and B
* Sickle cell anaemia
b. Diagnosing cancer - certain cancers are caused by specific and reproducible mutations: e,g.
Retinoblastoma - childhood cancer of the eye. The heritable form (germ line mutation of one of
the two retinoblastoma allelles): mutation is detected in all cells. Spontaneous form: only detected
in tumour tissue.
c. Blood group typing
d. Prenatal diagnosis - such as determining the sex of foetuses for those at risk of X-linked
disorders
PCR is one of the most versatile techniques invented, and has so many applications that this list
could go on for quite some time.
Downstream processing
It refers to the recovery and purification of biosynthetic products, particularly pharmaceuticals, from
natural sources such as animal or plant tissue or fermentation broth, including the recycling of salvageable
components and the proper treatment and disposal of waste. It is an essential step in the manufacture of
pharmaceuticals such as antibiotics, hormones (e.g. insulin and human growth hormone), antibodies (e.g.
infliximab and abciximab) and vaccines; antibodies and enzymes used in diagnostics; industrial enzymes;
and natural fragrance and flavor compounds. Downstream processing is usually considered a specialized
field in biochemical engineering, itself a specialization within chemical engineering, though many of the
key technologies were developed by chemists and biologists for laboratory-scale separation of biological
products.
Stages in Downstream Processing
A widely recognized heuristic for categorizing downstream processing operations divides them into four
groups which are applied in order to bring a product from its natural state as a component of a tissue, cell
or fermentation broth through progressive improvements in purity and concentration.
Removal of insolubles
Product Isolation
ProductPurification Product Polishing
A) 1 Mark Questions
1)
2)
3)
4)
5)
6)
What is biotechnology?
Define plasmid.
What are molecular scissors?
What do you mean by recognition sequence?
Which enzymes act as molecular glue?
What is elution?
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7) What are cloning vectors?
8) Name the sequence within a cloning vector from where the replication commence.
9) Mention the bacteria that acts as natural genetic engineer.
10) Name any two processes by which alien DNA is introduced into the host cell.
11) Expand the term PCR.
12) Name the microorganism from which the thermostable DNA polymerase required for PCR
is obtained?
13) What is a bioreactor?
14) What are the two main processes involved in downstream processing?
HINTS:
1)Large scale production and marketing of products and processes usin g living organisms,cells or
enzymes.
2)Autonomously replicating circular , extra-chromosomal bacterial DNA used in gene
manipulation.
3)Restriction enzymes.
4) Restriction endonucleases always cut DNA at a specific point by recognizing a specific
sequences of base pair known as recognition sequence.
5) DNA ligases
6)The ultimate step in the separation and isolation of DNA fragments through gel electrophoresis in
which separated bands of DNASs are cut out from the gel and extracted from the gel piece.
7) Cloning vectors are extra-chromosomal 'replicons' of DNA which can be isolated and can
replicate independently of the chromosome.. DNA of interest can be cloned into the vector and
replicated in host cells
8)ORI point
9) Agrobacterium tumefaciens
10)Micro injection,biolistics(gene gun)
11)Polymerase Chain Reaction 12) Thermus aquaticus
13)Large scale biotechnological product involves the use of bioreactor.
14) Separation and purification.
2-Marks Questions
1)Enlist the core techniques that pave the way for modern biotechnology.
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2) What is gene cloning?
3)Mention the three steps involve in genetically modifying an organism.
4) Why do bacteria possesses restriction enzyme ?
5)Mention one basic difference between restriction endonucleases and exonucleases.
6) What is a palindromic sequence? Give example.
7) What are ― sticky ends‖ and ―blind ends‖ ?
8)Mention the role of selectable marker in cloning vector.
9)What is insertional inactivation?
10) Howe can you make a bacterial cell competent to take up foreign DNA ?
HINTS:
1) ( a) Genetic engineering (b) maintenance of sterile ambience.
2) The process of cloning multiple copies of a gene.
3) (a) identification of DNA with desirable genes (b) introduction of the identified DNA into
the host and (c) maintenance of introduced DNA in the host and transfer of DNA to its
progeny.
4) By restriction enzyme bacteria can attack and destroy the phage DNA in a case of viral
attack and thereby prevent viral attack.
5) Exonucleases digest DNA from the flank ( beginning/end) of the DNA strands. Whereas
endonucleases catalyses the hydrolytic cleavage of DNA in the middle.
6) A segment of double-stranded DNA in which the nucleotide sequence of one strand reads
same in reverse order to that of the complementary strand. (always read from the same
direction)
7) Double stranded ends of a DNA molecule (without any overhangings) produced by the
action of certain restriction enzymes .-[blunt ends)/ Sticky ends - Double stranded ends of
a DNA 0molecule (with overhangings) produced by the action of certain restriction
enzymes
8) The selectable marker genes in a cloning vector allow fopr the selection and identification of
bacteria that have been transformed with a recombinant plasmid compared to
nontransformed cells.Some of the most common selectable markers are genes for ampicillin
resistance (ampR) and tetracycline resistance (tet R ) and the lacZ gene used for blue white
selection.
9) Insertional inactivation refers to the loss of activity of the selectable marker genes due to the
insertion of foreign DNA within the coding sequence of the marker gene in a transfected
bacteria.
3-Marks Questions:
1)Enlist the major steps in recombinant DNA technology.
163
2)Mention the steps involved in the separation and isolation of DNA fragments through agarose
gel electrophoresis.
3)Describe in brief the principle of DNA isolation through gel electrophoresis.
4)Highlight the salient features that are required to facilitate cloning into a vector.
5) Enumerate the major steps for isolation of DNA.
6) Draw a neat ,labeled diagram of (a) simple stirred tank bioreactor/ (b) sparged tank
bioreactor.
HINTS:
1) R-DNA Technology:
Restriction enzyme cuts double stranded DNA at its particular recognition sequence.
The cuts produce DNA fragments with cohesive ends
DNA from a plasmid was also cut by the same restriction enzyme
When two of the above mentioned DNA come together they can join by base pairing.
DNAligase enzyme is used to unite the backbones of the two DNA fragments ,producing R-DNA
2)Agarose gel electrophoresis:
Electrophoresis
Electrophoresis is a technique used to separate and sometimes purify macromolecules especially proteins and nucleic acids - that differ in size, charge or conformation.
Linear DNA fragments of different sizes are resolved according to their size through gels made of
polymeric materials such as polyacrylamide and agarose.
When charged molecules are placed in an electric field, they migrate toward either the
positive or negative pole according to their charge. In contrast to proteins, which can have
either a net positive or net negative charge, nucleic acids have a consistent negative charge
imparted by their phosphate backbone, and migrate toward the anode
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DNA is electrophoresed through the agarose gel from the cathode (negative) to the anode
(positive) when a voltage is applied, due to the net negative charge carried on DNA
When the DNA has been electrophoresed, the gel is stained in a solution containing the chemical
Ethidium bromide
Ethidium bromide is a fluorescent dye that intercalates between bases of nucleic acids and allows
very convenient detection of DNA fragments in gels under U-V radiations,
This compound binds tightly to DNA (DNA chelator) and fluoresces strongly under UV light allowing the visualisation and detection of the DNA.
Finally,, the separated DNAs are cut out from the gel and extracted from the gel piece(elution).
3) DNA When charged molecules are placed in an electric field, they migrate toward either
the positive or negative pole according to their charge. In contrast to proteins, which can have
either a net positive or net negative charge, nucleic acids have a consistent negative charge
imparted by their phosphate backbone, and migrate toward the anode
DNA is electrophoresed through the agarose gel from the cathode (negative) to the anode
(positive) when a voltage is applied, due to the net negative charge carried on DNA
4)Salient features of a DNA cloning Vectors:





Size: small enough to be easily separated from the chromosomal DNA of the host
bacteria.
Ori site; must have the site for DNA replication that allows the plasmid to replicate
separately from the host cell’s chromosome.
Multiple Cloning sites :a stretch of DNA with recognition sequence for many
different commonb restriction enzymes.
Selectable marker genes
RNApolymerase promoter sequence
Major steps for isolation of DNA:
Cell containing DNA is treated with lysozyme/cellulose/chitinase
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DNA along with RNA,Protein,lipd are released
Treatment with RNAase,protease to remove RNA And Protein
Appropriate treatment to remove other impurities
Addition of chilled ethanol to get precipitation of purified DNA
6) Consult NCERT Textbook page number 204
5-Marks Questions:
1) What do you mean by PCR? Briefly enumerate the major steps of PCR. Mention the utility
of PCR.
HINTS:
PCR is a cycle of three steps:
4. DENATURATION - the strands of the DNA are melted apart by heating to 95°C
5. ANNEALING - the temperature is reduced to ~ 55°C to allow the primers to anneal to
the target DNA
6. POLYMERISATION/EXTENSION - the temperature is changed to the optimum
temperature in order for the DNA polymerase to catalyse extension of the primers, i.e. to
copy the DNA between the primers.
The cycle is repeated over and over again - as many times as needed to produce a detectable
amount of product (DNA)
HIGH ORDER THINKING SKILLS (HOTS).
1) Why don’t restriction enzyme digest chromosomal DNA in bacterial cells ?
2) Why do bacteria have plasmids?
3) Why thermostable DNA polymerase is essential in PCR?
4)Eukaryotes do not have restriction endonuclease, then how they manage with normal
endonuclease enzyme?
5) It is advisable to use different restriction endonucleases to cut the vector DNA
and source DNA.Why ?
3 Uncontrolled recombinant DNA technology experiments is dangerous to
mankind. Comment on it.
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4)
=
+
Foreign DNA
+
plasmid
…………??…………
Complete the above sequence of diagrammatic representation and name it.
5 ). (a) Which is the most commonly used matrix in gel electrophoresis ?
(b) What is the source of it?
6) Find the ‘odd one out and write why that is ‘odd’
(a) Sal I, Pst I, Cla I, BamH I, pBR 322
(b) Bacteria, Virus, Gene-gun, Fungi
7) Detect the mismatch from the following and replace the
wrong match with a right one
(a) ECOR I –Bacteria
(b) Ethidium Bromidqe- Gel electrophoresis
(c) Lysozyme- Fungi
(d) Palindrome sequence-Restriction enzyme
8). Name the enzyme involved in the following process:
(a) Repeated amplification of DNA fragments.
(b) Formation of short piece of RNA strand for annealing.
(c) Breaking of bacterial cell to release DNA and other macromolecules.
(d) Cutting and rejoining DNA fragments.
(e) Formation of m-RNA
(f) Joining of foreign DNA fragments with plasmid.
9)Explain how recombinants and non- recombinants are differentiated on the basis of colour
production in the presence of a chromogenic substrate. Name that procedure.
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Chapter-12 BIOTECHNOLOGY & ITS APPLICATION
Biotechnology has given several useful products using microbes, plants, animals & their metabolic
machinery.
Applications- i) Diagnostic & therapeutic
ii) Genetically modified crops
iii) Waste treatment
iv) Energy production
v) Food processing
vi) Bioremediation
Application in agriculture
Genetically modified organisms (GMO)-Plants, bacteria, fungi, animals.Whose genes are altered by
manipulation.
Transgenic crops-Crops contain or express one or more useful foreign genes.
Advantages-i) More tolerant to stresses (heat, cold, drought).
ii) Pest resistants GM crops, reduced the use Chemical pesticides. Eg- BT-Cotton
iii) Reduced post harvest losses. Eg- Flavr savr tomato.
iv) Enhance nutritional value of food. Eg- Golden Rice (Vitamin A enriched).
v) Increased efficiency of mineral uses.
Bt- cotton -- BT stands for Bacillus thuringenesis (Soil Bacteria). Bacterium produces proteins
(Crystal Protein) that kills the insects. Remains as Protoxin (inactive) in bacteria, converted to toxins in
alkaline medium (i.e. in the gut of insects) and cause death of the insect.
Protection of plants against nematodes – Nematode, Meloidogyne incognita infects tobacco plants &
reduces yield. Specific genes (DNA) from nematodes introduced into the plants using Agrobacterium.
Genes produce sense and antisense Complementary RNA. Complementary RNA neutralizes the specific
RNA of nematodes by a process called RNA Interference and parasite cannot live in transgenic host.
In medicine- genetically engineered insulin—
Human insulin consists of Polypeptides chain A & B. Insulin secreted as Pheromone, which contains C
peptides, and it is removed during maturation.
In 1983, Eli Lilly, an American company prepared 2 DNA sequences coding for chains A & B.
Gene therapy – Genes inserted into the cells and tissues to correct certain hereditary diseases.
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ADA (Adenosine Deaminase) defiency can be cured by bone marrow transplantation.
Molecular diagnosis -- PCR (Polymesase chain reaction) used for early diagnosis of disorder.
Elisa (Enzyme Linked Immunosorbent Assay) used to detect AIDS
Biropiracy -- Some organizations and multinational companies exploit or patents bioresources of other
nations without proper authorization.
1) Name the bacterium that was the first biopesticides used on commercial scale in the world?
ANS- Bacillus thuringenesis
2) What do the terms Cry and cry represent respectively?
ANS- Cry—Protein, cry—Genes
3) What does ELISA stand for?
ANS- Enzyme Linked Immunosorbent Assay
4) Which Nematodes infects the roots of tobacco plants and causes a great reduction in yield?
ANS- Meloidegyne incognita
5) What is DNA Probe?
ANS- Short specific artificially produced segments of DNA.
6) Name the disease for which first chemical gene therapy was given?
ANS- ADA deficiency to a 4- years girl in 1990.
7) What is Alpha-lactalbumin? Where is it produced in human body?
ANS- Important human milk protein found in human breast milk.
8) ‗Crystal of BT toxin produced by same bacteria kill the bacteria themselves‘. Why?
ANS- It remains as protoxin (inactive form) in bacteria. It becomes
toxin in alkaline medium ( in gut of insects ).
9) Expand the terms :GEAC, SCID
ANS- GEAC- Genetic Engineering Approval Committee.
SCID- Severe Combined Immuno Deficiency
10) Which transgenic animal is used for testing the safety of Polio vaccine?
ANS- Mice.
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11) Name the first transgenic cow?
ANS- Rosie.
12) What are genetically modified organisms?
ANS- Organisms (plants, bacteria, fungi, animals) whose genes have been altered.
2marks questions
1) What was the speciality of the milk produced by the transgenic cow Rosie?
Ans- i) Contained alpha lactalbumin
ii) Nutritionally more balanced than normal cow milk
2)Name some techniques used for early molecular diagnosis of pathogens and genetic disorders?
Ans- i) rDNA technology
ii) PCR (polymerase chain reaction)
iii) ELISA (enzyme linked immune sorbent assay)
3) Explain why children eating golden rice are unlikely to suffer from nightblindnes?
Ans- i) It is genetically engineered with high levels of beta carotene and other carotenoids which enhance
vitamin A in rice .
ii) Lack of vitamin A causes night blindness .
4) Describe briefly how does Hirudin protein is being produced through a transgenic plant .
Ans- Gene encoding Hirudin chemically synthesized and transferred to brassica napus where it
accumulates in seed and purified and used as medicine. Hirudin protein stops blood clotting.
5) What is meant by RNA interference ? Explain .
Ans- Silencing of a specific mRNA due to complementary ds RNA molecule that bind to and prevents
translocation of the mRNA (silencing)
3marks questions
1) What are the potential risks ( Three ) and benefits(Three) of GM crops ?
Ans – Potential risks- i) Products of transgene - allergic or toxic
ii) Cause damage to natural environment
iii) Weeds also become resistant
iv) Can endanger native species
Benefits –i) More tolerant to abiotic stress.
ii) Disease resistant .
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iii) Enhanced nutritional value
2) What are cry proteins? Name the organism that produces it . How has man exploited this protein
to his benefit?
Ans – i) Protein crystals containing toxic insecticide.
ii) Produced by soil bacterium , Bacillus thuringenesis.
iii) BT toxic genes isolated and incorporated into several crop plants ( BT cotton , BT corn
) to provide resistance against insect pests.
3) What are probes ? How it is used in diagnosis of diseases?
Ans –
Probes are small (15-30 bases ) nucleotide sequences used to detect the presence of
complementary sequences in nucleic acid samples.
Single stranded DNA or RNA with radioactive molecules allowed to hybridize its
complementary DNA in clone cells . Followed by detection using autoradiography.
Clone containing unitated gene appear on photographic film.
5 marks questions
1)Explain the steps involved in the production of genetically engineered insulin?
Ans- i) Human insulin consists of 51 amino acids arranged in chains of A and B bearing 21 and
30 a.a respectively interconnected by disulphide bridges.
Diagram- Maturation of proinsulin into insulin after removal of c- peptide
ii) Insulin synthesized as prohormone has extra c -peptide which is removed during maturation.
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iii) In 1983 , Eli Lilly, American company prepared two DNA sequences similar to A and B chains of
human insulin(humulin).
iv) Chain A and B extracted and combined by creating disulphide bonds.
2) a) Name the nematode that infects and damages tobacco roots .
b) How are transgenic tobacco plants produced to solve this problem.
Ans – a) Melodegyne incognitia
b) i) Nematode specific genes isolated , cloned and introduced into tobacco plants
ii) ds RNA are produced that inititated RNA interference .
iii) mRNA translation silenced.
iv) Survival of the nematode not possible in the transgenic host plant.
3) Describe with examples why transgenic animals are produced ?
Ans-i) Transgenic animals produce useful compounds , created by introducing a porton of DNA that code
for
the products.
Example :-Alpha – 1 antitrypsin used for treating emphysema,.
ii) These animals help to test the safety of vaccines
Ex:- Polio vaccine is tested on mice
iii) More sensitive to toxic substances.
iv) It increases our understanding as to how genes could control the development of diseases.
v) The study of regulation of genes and how it affects the normal function.
Example:-Information is obtained about how insulin act as a growth factor .
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Chapter 13 ORGANISMS AND POPULATIONS
Capsule
Levels of organisation
1.organism
2.population
characteristics
growth rate
3.biotic community
4.ecosystem
5.biome
6.biosphere
Environment
a) abiotic factors
Temperature
Water
Light
Soil
b) RESPONSE TO ABIOTIC FACTORS –
Regulate
Conform
Migrate
Suspend
Adaptation
POPULATION ATTRIBUTES
POPULATION GROWTH-
Natality
+
Immigration
+
Population density
population growth and growth forms
change
Nt=N + B+I D+E
GROWTH CURVE
‗J‘ or ‗S‘ Shaped
dN=rN
dt
Change in population size
Density
dN
dt
Mortality
Emigration
Growth ModelsExponential growth
Logistic growth
Population interactionsPositive
mutualism
commensalism
negative
competition
predation
parasitism
ammensalism
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= rN K-N
K
13. organisms and populations
Ecology
# It is a branch of science.
# It deals with the interaction (i) Among organisms (ii) Between organisms (iii) Physical environment.
# Deals with four levels of organization
Levels of organisaton
BIOSPHERE
BIOME
COMMUNITY
POLULATION
ORGANISM
Organism
Individual of specific species e.g. cat, rat, human being, etc.
Population
# Group of individuals.
# Observed intra-specific competition for basic needs.
Community
# Aggregation of populations
# Observe both Intraspecific and Interspecific competition.
Biome
# Combination of various communities.
# Regulation type and associated fauna in specific climatic zone.
# Seasonal variation and annual variation lead to biome formation
# E.g. Artic and Alpine tundra, coniferous forest, temperate forest, grass land and desert.
Biome distribution
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Environment
Abiotic factors
Biotic factors
Temperature, soil,
water, light
Microorganisms, plants,
Animals
Temperature
# Average temperature varies seasonally
# Decreases from equator to poles and plains to mountains
# Temperature ranges from sub Zero to 50 C in tropical forests
# Function and distribution of organisms temperature dependent.
# Organisms Eurythermal or Stenothermal
# Organisms affected by Global Warming.
Water
# Influences life of organisms. No life without water.
# Productivity and distribution of plants water dependent.
# Quality important for aquatic organisms
#Organisms Euryhaline or Stenohaline.
Light
# Photosynthesis and release of oxygen light dependent.
# Sciophytes need use diurnal and seasonal light intensity of forage, migration and reproduction.
# Distribution of algae at different depths light dependent.
Soil
# Nature and proportion of soil in a place depends on climate, weathering process and types of soil.
# Soil composition, grain size and aggregation determine percolation and water holding capacity of soil.
# Physical and chemical properties determine type of plants and Animals that survive in a habitat.
# Biotic sediments determine type of Benthic Animals.
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Response to environmental condition
Regulation
suspention
organism
conformation
migration
Regulation
# Organisms maintain homeostasis achieved by physiological and behavioral means
# Have constant body temperature (Thermoregulation)
# Constant osmotic concentration (Osmoregulation)
Conformation
# Cannot maintain constant internal Environment
# Body temperature changes with the ambient temperature
# Osmotic concentration of body fluid changes with the ambient concentration of medium.
# Thermoregulation energy expensive, heat loss or gain is a function of surface area of body.
Migration
Occurs in stressful condition
Organism moves away temporarily to another habitat.
Birds undertake long distance migration.
Susppension
Organisms suspend their metabolic activities during stressful condition
Resume their function at the return of favorable conditions.
E.g. Hibernation of Frog, Reptiles, Polar Bear etc
Aestivation in Snail and Fish.
Seed dormancy.
Adaptation
Morphological, physiological and behavioral changes that enable organisms to adjust to the
Ever changing environment
E.g. Kangaroo rat survives in desert conditions through internal oxidation of fat,
removing concentrated urine of les quantity.
Allen‘s rule-cold climate mammals have shorter ears and limbs to minimize heat loss.
Polar mammals like seals have blubber to prevent heat loss.
Burrowing habit to escape form heat
Higher count of RBC, Hb at high altitudes.
Population attributes
*Birth Rate
*Death Rate
*Sex Ratio
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*Population density.
Age pyramids
# Three ecological ages:
# Pre-reproductive, Reproductive and Post-Reproductive
# High proportion pre-reproductive individuals occur in expanding population
# Pre-reproductive individuals are uniform in stable population.
# Pre-reproductive individuals are less in Declining population.
Representation of age pyramids for human population
Post
Reeproductive
Reproductive
Pre
Reproductive
EXPANDING
STABLE
Population growth
Factors that affect the size of population
Food availability
Weather
Predation pressure
Competition
Density of population at any time at a given place depends on
Natality, Mortality, Emigration Immigration
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DECLINING
Population growth models
Exponential growth : dN/dt rN
Logistic growth
: dN/dt rN K N/K
Where
dN = Difference in the number of individuals in a population.
dT = Difference in time.
rN = intrinsic rate of natural increase in number of individuals
K = carrying capacity of the area
N = number of existing individuals in a population.
Factors that affect population density
IMMIGRATION
I
NATALITY
B
POPULATION DENSITY
N
EMIGRATION
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MORTALITY
D
Types of population interactions
Interaction
Species a
Mutualism
Predation
Parasitism
Commensalism
Competition
Ammensalism
Species b
Mutualism
Both the species get benefited.
Lichens Relationship between Non-photosynthetic Fungus and
photosynthetic Algae or Cyanobacteria.
Mycorrhiza Asociation between Fungui and Higher Plants like Pinus.
Plants and insects for pollination
Orchid ophrys and male bee a good example for co-evolution of plants and Animals.
PREDATION
One species get benefited and the is harmed.
Tiger and Deer
Snake and Frog
Herbivores and plants
Competition
Both the species are harmed.
Flammingoes and resident fishes compete for the common food zooplankton in
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South American lakes.
Abington Tortoise and goats in Galapagos Islands for food.
Gouse‘s ―Competitive Exclusion Principle‖ -Two closely related species competing for the same resource
cannot co-exist indefinitely and trhe competitively inferior on will be eliminated eventually.
Parasitism
One species gets benefit and the other is harmed.
Parasites
Endoparasites
Liver fluke, plasmodium
ectoparasites
lice, ticks
brood parasites
koel
Adaptations of parasites
# Loss of sense organs
# Presence of adhesive organs or suckers
# Loss of digestive system
# High reproductive capacity.
Ammensalism
One species hurts the other but the other is not affected.
Penicillium secretes Penicillin and kill Bacteria but by this Penicillium does not benefit.
Algal bloom leads to death of fishes, but the death of fishes is of no use to the algal bloom.
Commensalism
One species benefits and the other neither harmed nor benefited.
The cattle egret catches the insects disturbed by moving cattle, but the cattle neither harmed
nor benefited.
Another example
The clown fish gets protection from predators by close association with sea anemone,
but the sea anemone has no effect.
Very short type questions (1 mark)
1. Define Ecology.
Ans. Branch of biology, which studies the relationships of
living organisms with the abiotic and biotic components of their environment.
2. Name the factors that account for the formation of major biomes.
Ans. A) The annual variations in the intensity and duration of temperature and
B) The annual variation in precipitation.
3. Most living organisms cannot survive at temperature above 45 C. How are
some microbes able to live in habitats with temperature exceeding 100 C.
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Ans. Possess some heat-resistant or thermostable protein/enzymes and an
array of biochemical adaptations.
4. Why many of the fresh water animals cannot live for long in sea water or vice versa?
Ans. They would face osmotic problems.
5.
Define homeostasis.
Ans. It is the phenomenon in which the organisms maintain a steady
constant environment, despite varying external environmental conditions.
5. Why is the polar region not a suitable habitat for tiny humming birds?
Ans. Have a larger surface area to body volume ratio, tend to
lose heat fast when it is cold outside, have to spend more
energy to generate body energy.
6. What is meant by Allen‘s rule?
Ans. Allen‘s rule refers to the minimizing heat loss in animals by possessing shorter ears and limbs.
7. Why do people living in high altitudes have a higher red blood cell count and total haemoglobin?
Ans. To compensate for the low atmospheric pressure. Low oxygen content of air prevailing at high
altitudes.
8. When does a population growth curve become J-shaped?
Ans. Sigmoid growth curve represents logistic growth, Growth is slow initially, becomes rapid , then
becomes steady as resources become limiting.
9. What is the ecological principle behind the biological control methods of managing the pest
insects?
Ans. Predation, interspecific interaction where one animal kills and consumes the other weaker animal.
10. Why is the female mosquito not considered a parasite, though it needs our blood for
reproduction?
Ans. The female mosquito is not considered a parasite because; it does not take shelter on our body
and does not harm the body.
Short answer type questions (2 marks)
1.Name the four major biomes found in India?
Ans. (i) Tropical rain forest
(ii) Tropical deciduous forest
(iii) Desert
(iv) Sea coast
2. How does light influence the life of living organisms?
Ans. Intensity and duration of light influence.
Foraging , migratory activities and reproduction.
3. Why are very small animals generally not found in Polar Regions?
Ans. Heat loss or gain is a function of the surface area. Small animals have a larger surface area
relative to their volume. So loose heat rapidly.
So they tend to lose body heat very fast when it is cold outside consequently they have to spend more
energy to generate body heat.
Considering the cost and benefits of energy expenditure very small animals are generally not found in
Polar Regions.
4. List the attributes that populations but not individuals possess.
Ans. (i)
Birth rate
(ii)
Death rate
(iii)
Sex ratio
(iv)
Age distribution
5. Biomass is a more meaningful measure of population size. Explain with an example.
Ans. (i) Population large the total number is not an easily adoptable measure. Counting takes long
time or practically impossible
(ii) There is no need to know the absolute population size for some investigations..
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(iii) Number may sometimes be misleading e.g. In a given area there are 200 Parthenium plants and a
single banyan tree.Here biomass size of the banyan tree is much more than those of 200 Parthenium
plants.
6. Why is logistic curve growth model considered more realistic? Explain.
Ans. No population of any species in nature can have unlimited resources to permit exponential
growth.
Since resources are finite and become limiting, there is competition among individuals for the limited
resource and eventually only the fit individuals will survive and reproduce.
7. Name the important defence mechanisms in plants against herbivory.
Ans. (i) Thorns and spines are most common morphological means of defence.
(ii) Plants produce and store certain chemicals which may
(a) Make the animal sick
(b) Interfere with digestion
(c)Be poisonous to kill them.
Short answer type questions (3 marks)
1.How do organisms manage with stressful conditions existing in their habitats for short duration?
Explain with the help of one example each.
Ans. (i) Organism moves away from the stressful area to a comfortable area, returns back when the
stressful period is over
e.g. Birds from Siberia migrate to Bharatpur Sanctuary in Rajasthan.
(ii) Animals which cannot migrate show
hibernation during winter
or aestivation in summer
or enter into diapause.
(iii)Bacteria, Fungi and lower groups of plants produce thick walled spores which germinate under
suitable conditions.
(v)
In higher plants seeds and some other vegetative reproductive structure serve
the purpose.
2. What is brood parasitism? Give an example. What adaptation has evolved in this
phenomenon?
Ans. * One species lays eggs in the nest of another bird, lets the host incubate them.
e.g. Cuckoo lays eggs in the nest of a crow.
The eggs of the parasite resemble with the eggs of the host in colour, size. Reduce chances of the
host bird detecting the foreign eggs and ejecting them from nest.
3. Name and explain the kind of interaction in the following.
1. Algae and Fungi in Lichens
2. Head Louse and Humans
3. Hermit Crab and Sea Anemone
(i) Interaction of mutualism where the two species are equally
benefited.
Fungus provides protection, helps in absorption of water and minerals,algae provide food for
the Fungus.
(ii) This is case of Parasitism where the louse is an ectoparasite.
Parasite takes shelter on humans and also derives nutrition.
(iii) It is commensalisms where one species is benefited and the other is neither benefited
nor affected.
Sea Anemone is benefited as it does not have to move to places rich in nutrients, while hermit crab is
neither benefited nor harmed.
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Long answer type questions (5 marks)
1.Define the following terms and give an example each.
a) Commensalism
b) Parasitism
c) Camouflage
d) Mutulism
e) Interspecific competition.
Ans. Commensalism.
i)
interspecific
ii)
one species benefited, other neither benefited nor harmed,
E.g. A clown fish living among sea anemone.
b) Parasitism
i)
interspecific
ii)
one species takes food and shelter from another
iii)
damages host
iv)
parasite benefited host harmed.
c) Camouflage
Adaptation where the animal blends with the surroundings to escape detection by predator e.g
Frogs have olive green skin with patches of chromatophores to camouflage with grass.
d) Mutulism
Both the species are mutually benefited ,e.g. An alga and a fungus in lichen.
e) Inter specific competition.
Individuals of two different species compete with each other for certain resources and both are
harmed
2.What is an age pyramid? What do they show about human population? Represent diagrammatically the
different shapes of age pyramids and mention what each of them represents.
Ans. Graphic representation of the age distribution ,i.e. per cent individuals in different age group of a
population.
For human population, the age pyramids generally show age distribution of males and females in a
combined diagram.
Expanding
Stable
Declining
* Shape of the age pyramid reflects growth status of the population.
* Size of the population tells us about its status in the habitat.
* Ecological process is investigated in terms of a change in the
population size.
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CHAPTER-14 ECOSYSTEM
A.G.Tansley coined the term ecosystem in1935.
Types-a)Terristrial-Forest, grassland, trees, desert etc. b)Aquatic-Pond, lake, river etc.
Components –a)Biotic –Producers, consumers,decomposers b)Abiotic-Air,water,soil,temperature.
ii) stratification- vertical distribution of different species in different strata.
iii) tropic organization- Food relationship of producers and consumers.
1) Productivity – Two types – i)primary productivity-I) amount of bio-mass produced per unit area
.It is of two types a)GPP(Gross primary productivity) – Rate of synthesis of organic matter per unit area
.
b)NPP(net primary productivity)- NPP = GPP –R (respiration )
ii) secondary productivity – Rate of formation of new organic matter by consumers .
2) Decomposition- Breakdown of complex organic matter into simpler inorganic
substances by decomposers .
Steps in decomposition – i) Fragmentation of Detritus
ii) Catabolism
iii) leaching
iv) Humification and mineralisation
3) Energy flow – Flow of energy is governed by law of thermo dynamics.
a. Energy flow unidirection from producers to consumers .
b. In each trophic level there is loss of 10 % energy(10%Law)
4) Nutrients cycle or biogeochemical cycle – Different nutrient cycles are
i)
Carbon cycle
ii)
Phosphorus cycles
Specific place occupied by organism in the food chain. It is a division of food chain .
STANDING CROP
Biomass present in atrophic level at a particular time. Biomass is the dry weight of organism.
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Food chain is of two types –
i)Detritus food chain – Starts with organic matter or detritus.
Detritus
Earthworm
Frog
Death
death
Snake
death
Decomposers (detrivores )
ii) Grazing food chain – Known as predator food chain.
Grass
Goat
(producer)
(P.consumers)
Man
(S.consumers )
Food web – Natural interconnected food chains .i)
ii)
unidirectional
loss of 10 % of energy in each trophic level
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Peacock
death
Ecological pyramidsGraphical representation of food or energy relationships between organisms of different trophic levels .
Types – 3 types -i) Pyramid of numbers – Graphical representation of the number of
individuals per unit area. It is mostly upright . It may be upside down .
Pyramid of number –upside up and upside down.
Pyramid of biomass
Graphical representation of biomass per unit area of different trophic levels . May be upside up
and upside down.
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Pyramid of energy
Amount of energy trapped per unit time and area in different trophic levels . It is always upside
up .
Gradual and fairly predictable changes in species composition of a given area .
Types – i) primary succession – Succesion on bare land ex:- bare rocks ,newly created ponds etc.
ii)Secondary succession – Occures in an area where there was vegetation earlier. Soil or sediment
present that is why it is faster than primary succession .
Two types ,based on nature of habitats.
i)
hydrach succession – Succesion in water or wet areas
Steps in hydrach Phytoplanktons--- Floating angiosperms---Rooted hydrophytes---sedges---grasses---shrubs and trees
(Pioneer)
(climax)
(Seral)
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ii)
Xearch succession – succession on bare rock
Stages or steps –
Lichens---mosses---herbs---shrubs---trees
(pioneer)
(climax)
(seral)
i) Carbon cycle
ii)Phosphorus cycle
Chapter-14 Ecosystem
LEVEL1:-
Q1 ) What is biomass ?
Ans – Total dry weight of organic matter present in an organism .
Q2 ) Name the four important functional aspects of ecosystem .
Ans – i) Productivity ii) Energy flow iii) Decomposition iv) Nutrient cycling
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Q3) Name the two forms of reservoir of carbon that regulate the ecosystem carbon cycle
. Ans – Oceans and atmosphere .
Q4) Name the dominant producers in a deep aquatic ecosystem .
AnsPhytoplankton. Q5)
What is NPP? ANS
–NPP= GPP-R
Q4. What are the two basic catagories of ecosystem? Give example.
Ans-a) Terrestrial-Forest, grassland, desert.
b) Aquatic-Pond, lake, sea, ocean
Q5.What is food chain? Give an example.
Ans-a) Food and feeding relation among organisms makes a chain like structure
b) Grass—Deer—Lion
Q6. Describe the major components of ecosystems.
Ans- a) Biotic-i) Producer-green plants.
ii) Consumers-primary, secondary,tertiary and decomposers.
b) Abiotic-i) Physical and climatic factors-soil, temperature,light, humidity.
ii) Chemical factors-inorganic chemical substances (sodium, potassium, nitrogen etc.)
organic substances-(humus, protein, fat etc.)
LEVEL 2
Q1) What do you mean by transducers ?
Ans – Producers are called transducers because producers change light energy into chemical energy .
Q2) What is meant by productivity of a trophic level ?
Ans - Rate of synthesis of energy containing biomass per unit area in unit time .
Q3) Which species is the pioneer species on a bare rock
Ans – Lichen
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Q4.What are decomposers? Write their function.
Ans-a)Saprotrophs feed on dead bodies of
organisms, b) Decomposition and
mineralization.
Q5.What is the difference between gaseous and sedimentary
cycle? Ans-a) Gaseous-Reservoir in atmosphere ,Nitrogen cycle
b) Sedimentary-Soil,e.gphosphorus.
Q6.Mention two factors by which productivity is limited in an aquatic ecosystem.
Ans-a) Light-decreases with increasing water depth.
b) Nutrient –Limiting factor in Deep Ocean
Q7.Expand PAR, How much PAR is used in gross primary productivity?
Ans-a)PAR-Photosynthetically active radiations
b) 2-10% is used.
Q8.Give account of factors affecting the rate of decomposition.
Ans-a) climatic factor – i)temp ii) soil
) chemical quality of detritus
Higher temp and moist condition – high rate of decomposition
Dry soil , High temp – Low rate
Q9) What are ecological pyramids ? Mention its limitations .
Ans –a) Arrangement of trophic levels from producers to top carnivores forms pyramid like structure
3 types – i) Pyramid of number
ii) Biomass
iii) Energy
Limitations – i) Assumes simple food chain
iii)
Single species may operate at two or more trophic levels.
Q10 ) Explain carbon cycle with ray diagram .
Ans – Given in text.
Q11. Give an account of energy flow in an ecosystem.
Ans- Rate of energy transfer between the organisms of different trophic levels is called energy flow.
Energy flow is unidirectional, 10% loss of energy in each trophic levels.
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2-10% PAR captured by green plants.
191
Energy flow diagram from the text.
LEVEL 3
Q1) Why the pyramid of energy is always upright ?
Ans – Because when energy flows from one trophic level to another trophic level , always some
energy is lost as heat .
Q2) What is bioenergetics ?
Ans – Transformation of solar energy into chemical energy by producers .
Q3.Why is the length of a food chain in an ecosystem generally limited to 3-4 trophic levels?
Ans –As 90% energy is lost in the from heat from one trophic level to another, residual energy
decreases drastically within 2-3 trophic levels.
Q4.What are the differences between detritus and grazing food chains?
Ans-a) Detritus-dead and decaying organic matter.
b) Grazing-Living green plants.
Q5.Briefly describe the process and products of decomposition.
Ans-Breakdown of complex organic matter by decomposers.
a)Process-i)fragmentation
ii)leaching
iii)catabolism.
Humification and mineralization –humification leads to accumulation of dark colour substance called
humus.
Mineralisation result in release of inorgranic substances. b
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Q6 .Describe pond as an ecosystem .
Ans- Pond has biotic and abiotic components
a) Biotic – Phytoplankton ,Zooplankton , small fishes , large fishes , frogs , snake
,etc. b) Abiotic - water , dissolved organic and inorganic substances ,sunlight , temp .
Phytoplankton (microscopic plants ) – producers .
Zooplankton (microscopic animals ) – primary
consumers Small fishes - secondary consumers
Large fishes , frog, snails – tertiary consumers
Q7.What is xerosere? Describe the process of succession on a bare rock.
Ans-a) Succession on bare rock.
b) Steps in Xerosere i) Lichens-Pioneer Community.
ii) Mosses
iii) Herbs
iv) Shrubs
v) Trees-Climax community.
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Chapter – 15 BIODIVERSITY AND CONVERSATION
Biodiversity is defined as the totality of genes, species and ecosystems of a given region,i.e.the combined
diversity at all levels of biological organisation.
GENETIC DIVERSITY
SPECIES DIVERSITY
BIODIVERSITY
ECOLOGICAL DIVERSITY
192
More than 70% of all the species are animals. Among animals insects are the most species rich
taxonomic group.
Plants comprise no more than 22% of all species.
1) Lattitudinal gradients – species diversity decreases as we move from equator to poles.e.g.
Columbia (near equator) has 1400 species of birds and Greenland (at 71degree North) has only
56species .
Speciation is generally a function of time. Temperate region is subjected to
glaciation.TropicaL regions have remained undisturbed .
2) SPECIES –AREA relationships :
S=CAZ
LogS=logC+ZlogA
ALEXANDER VON HUMBOLDT observed within a region species richness increased with
increasing explored area but only up to a limit.
The relation beween species richness and area for a wide varity of taxa turns out to be a rectangular
hyperbola.
On a logarithmic scale the relationship is a straight line as in a eqution
LogS = logC +Z log A
193
Where
S= species richness,A = Area,Z = slope of the line(regression coefficient),C = Y- intercept
Loss of biodiversity
Loss of biodiversity in a region may lead to
1)decline in plant production
2)lowerd resistance to environmental changes such as drought.
3)increased variability in certain ecosystem proesses such as plant productivity, water use,pest &
disease cycles.
Four major causes of biodiversity loss
i)Habitat loss and fragmentation
ii)over exploitation
iii)Alien species invasions
iv)Co-extinctions
Biodiversity conservation
Reasons for conservation can be grouped into three categories: a)narrowly utilitarian-for deriving
direct economic benefit from nature.
b)broadly utilitarian-as biodiversity plays a major role in many ecosystem services.
c)ethical-we need to realise that every species has an intrinsic value and we need to pass on
our biological legacy to future generations in good order.
How to conserve biodiversity:
IN SITU CONSERVATION – Threatened /endangered plants and animals are provided with urgent
measures to save from extinction in wildlife sancturies, national parks & biosphere reserves, sacred
groves.
Biodiversity hotspots – regions with very high levels of species richness.e.g.western ghat,
Himalaya.
EXSITU CONSERVATION –Threatened animals & plants are taken out from their natural habitat &
placed in a setting where they can be protected and given care as botanical gardens, zoos, seed/pollon
banks, gene banks etc.
194
Chapter – 16: Environmental Issues
Pollution
Any undesirable change in physical, chemical or biological characteristics of air, land, water or soil which
harms the human beings.
POLLUTION
AIR
WATER
SOIL
POLLUTION
POLLUTION
POLLUTION
NOISE
POLLUTION
Pollutants
Agents that bring about pollution E.g. smoke, dust, pollen, chemical pollutants,
wastes from hospitals, E-wastes etc.
Biodegradable and non -biodegradable pollutants
Ways of removing particulate matter
1. Electrostatic Precipitator
Discharge corona
Negatively charged wire
Dirty Air
Clean air
Dust particles
Collection plate grounded
195
Electrostatic precipitator
2. SCRUBBER
3. Proper maintenance of Automobiles
Advantage of cng over diesel
CNG burns most efficiently
Cheaper
Cannot be siphoned,
Cannot be adulterated.
Problems in use of cng
Difficulty in laying down pipelines
Non-assurance of uninterrupted supply
Steps taken in delhi to reduce pollution
Phasing out old vehicles
Use of unleaded petrol
Use of low sulphur Petrol and Diesel
Use of catalytic converters in vehicles
Application of stringent pollution level norms for vehicles.
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Noise pollution
It is undesirable high level of sound.
Harmful effects of noise pollution
Psychological and Physiological disorders
Damage of eardrums and hearing ability
Cause Sleeplessness, increased heartbeat altered breathing pattern, stress etc.
Steps to be taken to control noise pollution
Use of sound absorbent materials or by muffling noise in industries
Demarkation of horn free zones around hospitals and schools.
Permissible sound levels of crackers,
Timings after which Loudspeakers cannot be played
Water pollution
Biological Oxygen Demand (BOD) indicates the rate of uptake of oxygen by microorganisms in a
sample of water.
It shows the presence of organic matter in water, Greater the BOD more is the polluting potential. Less
is BOD, less oxygen will be consumed if all organic matter
in a litre of water is oxidized by Bacteria completely.
Effects of bod
Bacteria consume dissolved oxygen for biodegradation of organic matter high in downstream areas and it
causes of mortality of fish and other aquatic organisms.
Algal bloom
It is free floating (Planktonic) Algae.
Imparts a distinct colour to water bodies
Cause deterioration of water quality and fish mortality.
Some blooms are toxic to humans and Animals.
Water hyacinth (Eichornia crassipes)
World‘s most problematic aquatic weed
Called as ‗Bengal Terror‘ Grows faster than our ability to remove.
197
Biomagnification
Increase in concentration of the toxicant at successive tropic levels
Biomagnification of ddt
Water
0.0003 ppm
Zooplankton
0.04 ppm
Small Fish
Large Fish
0.5 ppm
2 ppm
Fish-eating Birds
5 ppm
Aquatic food chain
Eutrophication
Natural ageing of lake by biological enrichment of its water.
Cultural or accelerated eutrophication
Acceleration of ageing process of a lake by effluents from industries and homes.
Integrated waste water treatment in arcata
It consist of two steps
a) Conventional sedimentation, filtering and chlorine treatment,
b) Passing this water through marshes for neutralization absorption and assimilation of pollutants.
c) Upkeep of this project by FOAM (Friends Of Arcata Marsh).
SOLID WASTES
Biodegradable
Recyclable
Non-Biodegradable
Ecological sanitation (Ecosan )
A sustainable system for handling human excreta without using water but with composting method.
Advantages of ecosan
a) Wastage of water is reduced
b) Practical and efficient
c) Hygienic and cheap
d) Excreta can be recycled and used as natural fertilizer.
198
Hospital wastes
Syringes, discarded medicines, Used gloves, Post operative materials etc
Should be treated before disposing off.
E-wastes
Unused or damaged computers, calculators, mobile phones etc
Developed countries have plants for recycling e-wastes for recycling of metals.
In developing countries e-wastes are buried in landfills or incenerated.
Agro chemicals
Chemicals used in agricultural fields. Fertilizers, pesticides, weedicides etc.
They are toxic to even non target organisms.
Excess fertilizers cause Eutrophication.
They cause soil pollution
Advantages of organic farming
Economical
Wastes do not get accumulated but recycled
Does not cause Eutrophication
Radioactive wastes
Emit radiations and damage biological organisms.
Nuclear wastes are called potent pollutants, as they are lethal even in lower doses.
Disadvantages of nuclear plants
May happen accidental leakages
Unsafe disposal of radioactive wastes
Radiation emitted cause mutations in organisms
Radiation causes genetic disorders
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Green house effect
Earth‘s atmosphere acts as a cover, which allows heat and light to enter in, but heat is not escaped thus
warming up the earth.
Green House Gases:-Carbon dioxide, methane etc.
Ozone
Triatomic molecule of oxygen.
Found in stratosphere of atmosphere.
CFCs discharged from lower atmosphere move upward
UV rays act on these CFCs and release chlorine atoms.
Chlorine degrades ozone and release molecular oxygen
This process is irreversible and thus ozone is depleted.
Ozone hole
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Soil erosion
The removal of top fertile layer due to human activities
Reasons: -
Over cultivation
Over grazing
Deforestation
Improper irrigation practices
Waterlogging
The crops may droop
Leads to salinity of the soil.
Slash and burn agriculture/jhum cultivation
Farmers cut down the trees of the forest and burn the plant remains.
Ash is used as fertilizer and land is used for farming or cattle grazing
Later, Land is left uncultivated for several years for replenishment of minerals
Effects of deforestation
Leads to global warming due to excess carbon-dioxide
Loss of biodiversity
Damage to hydrological cycle
Leads to soil erosion
Desertification of land
Reforestaton
Restoring forest that was existing earlier
E.g. Observing Van-Mahotsavas
It also occurs naturally
Aforestation
Developing a forest in a new area where no such forest existed in that area.
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A case study of peoples participation in forest conservation
A king of Jodhpur wanted to arrange wood for his new palace in 1731.
Few Bishnois hugged the trees and asked to cut them first rather than cutting trees.
365 persons lost their lives in this act
A small temple is now present there in remembrance of this act
Amrita Devi Bishnoi Wild Life Protection Award is instituted for individuals of rural areas who take
keen interest in protecting wild life.
Chipko movement
It was started by local women of Garhwal, They hugged the trees to protect them from the
axes of contractors.
Joint forest management (jfm)
Started y Government of India in 1980
Local communities worked with the government to save the forest.
Communities get forest products for
encouragement.
Chapter-16 Environmental issues
LEVEL 1
1. Define eutrophication.
Ans. Nutrient enrichment in water bodies leading to depletion of oxygen and loss of life
supporting environment.
2. What is biomagnification?
Ans. Increase in the concentration of certain toxic chemicals at succesive trophic levels.
3. What is BOD?
Ans. Biological Oxygen Demand is the measure of organic matter in any water sample.
4.Which is the world‘s most problematic weed, also known as ―terror of Bengal‖
Ans. Eichornia crassipes (Water hyacinth)
Differentiate between biodegradable and non-biodegradable wastes.
Biodegradable wastes
Non-Biodegradable wastes
203
*Can be broken down into harmless simple
compounds by the action of decomposers.
*Cannot be broken down by microbes and
get accumulated in the biosphere
*Can be used as manure
*Enter the food chain
*Cause little pollution
*Cause biomagnifications
5. Describe Chipko Movement.
Ans. It was launched in Garwhal, Himalayas by Sh Sunder Lal Bahuguna in 1974.
Local women showed enormous bravery in protecting the trees from the axes of the contractors
by hugging them.
6. Mention harmful effects of noise pollution on human
health. Ans. Stress
Altered breathing pattern
Increased heart beating and blood pressure
Sleeplessness and headache
Hearing impairment.
LEVEL 2
1. What is meant by algal blooms? What is its significance?
Ans. Excess growth of certain phytoplanlktons due to excess nutrients in water causes Deteriorates
water quality, leads to fish mortality.
2 What is Jhum cultivation?
Ans Farmers cut down the tress, burn, use cattle for grazing and then allow the land to recover.
3 What is snow blindness?
Ans. Inflammation of cornea caused by a high dose of UV-B radiation.
4. Mention the harm caused by fine particulate matter to human beings?
Ans. (i) Cause respiratory problems
(ii) Irritation of eyes
(iii) Inflammation of lungs
(iv) Premature death.
5.What are the advantages of Organic
farming? Ans. Economical procedure as recycling
takes place.
Waste not accumulated but recycled
Efficiency and utilization of resources increased
204
Does not lead to eutrophication.
6. How do radioactive wastes cause damage to living
organism? Ans. Cause mutations in living organisms at a very high
rate.
Lethal in high doses
Causes cancer and other
disorders. Reduces the
vegetation cover.
7. What measures should be taken to reduce global
warming? Ans. Reduce use of fossil fuel
Efficient use of energy.
Avoid deforestation
Reduce human
population Control
green house gases.
8. Write a short note on ozone
depletion. Ans. Ozone found in
stratosphere.
CFCs discharged from lower atmosphere move upward. In stratosphere UV rays act on these
CFCs release chlorine atoms.
LEVEL 3
1.
What is the effect of DDT in birds?
Ans. DDT disturbs calcium metabolism in birds, thinning of egg shell and premature breaking
of
eggs leads to decline in bird population.
2.. What do you understand by ‗Ecosan‘?
Ans. Ecosan are the toilets which use compositing method for ecological sanitation.
3.. Why are nuclear wastes called potent pollutants?
Ans. Because they are lethal even at lower doses and cause damaging disorders.
4. Mention two problems that have arisen due to green revolution. Ans.
Water logging and soil salinity.
205
5. What is the effect of DDT in birds?
Ans. Disturbs Calcium metabolism
Thinning of egg shells and premature breakage of eggs,
Decline of bird population.
6. Write an account on Ecological sanitation (Ecosan).
Ans. A sustainable system for handling human excreta, using dry composting toilets.
Practical, hygienic, efficient and cost-effective solution to human waste disposal
Human excreta can be recycled into manure
Used in Kerala and Sri Lanka.
7. What is ecological sanitation? What are its advantages?
Ans. It is sustainable system for handling human excreta without using water but by
composting
method.
Advantages
Hygienic, practical and efficient
Conserves water
Can be recycled and acts as a natural fertilizer.
8. How can we reduce automobile pollution?
Ans. Un-Leaded Petrol- Reduces lead pollution in air.
Low Sulphur Diesel- Reduces sulphur pollution in air
Four
stroke engines
to reduce emission of
unburnt
hydrocarbons. Tube-Ups to increase air-fuel ratio and help in
better combustion. Catalytic Converters to reduce pollution.
CNG to reduce pollution and conserve fossil fuels.
9.Mention the adverse effects agrochemicals.
Ans. They are toxic to non-target organisms.
They cause soil pollution
Excess fertilizers cause eutrophication.
Chlorine degrades ozone and release molecular oxygen (O3
O2)
In this reaction chlorine acts, as catalyst and loss ozone is irreversible
10..Mention the Supreme Court directions to the Government to reduce pollution.
Ans. Switch over to CNG in public transport system
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Enforcement of Euro II norms for vehicles.
Compulsory periodic check up of pollution
Use of unleaded petrol
Low sulphur petrol and diesel
Catalytic converters in vehicles
Phasing out of old vehicles.
11. a) Explain the functioning of electrostatic precipitator with the help of a diagram.
b) Mention the consequence if the electrostatic precipitator does not work in a power
plant.
Ans. Used for removing particulate air pollutants.
Removes about 99
of the particulate pollutants from the exhaust of thermal power plants.
Electrode wires that are maintained at several thousand volts, which release electrons.
Electrons become attached to dust particles giving a net negative charge.
Collecting plates are grounded and attract the charged dust particles.
Velocity of air between the plates must be low enough to allow the dust particles to fall.
If electrostatic precipitator of a thermal plant stops working, all the particulate pollutants get
released and pollute the air.
Discharge corona
Negatively charged wire
Dirty Air
Clean air
Dust particles
207
Collection plate grounded
ELECTROSTATIC PRECIPITATOR
Word List for concept mapping
POLLUTION
Undesirable change in environment
POLLUTANTS
Agents that cause pollution
WAYS OF REMOVONG PARTICULATE MATTER
Electrostatic precipitator
Scrubber
Controlling vehicular pollution –Use of CNG
NOISE POLLUTION, ITS EFFECTS AND METHODS OF CONTROL
WATER POLLUTION AND ITS CONTROL
208
Biological Oxygen Demand
Algal Bloom Biomagnification
Eutrophication
Accelerated Eutrophication WASTE
WATER TREATMENT Case study
of Arcata
FOAM
SOLID WASTES
Municipal solid wastes
Biodegradable, Recyclable and Non-Biodegradable
A case study for Plastic Waste
E-wastes.
A case study of organic farming
RADIOACTIVE WASTES
GREEN HOUSE EFFECT AND GLOBAL WARMING
OZONE EPLETION IN THE STRATOSPHERE
Dobson units, CFCs, Snow-blindness, Montreal Protocol.
SOIL EROSION AND DESERTIFICATION.
WATERLOGGING AND SALINITY DEFORESTATION
SLASH AND BURN AGRICULTURE
REFORESTATION
CASE STUDY OF PEOPLE‘S PARTICIPATION IN CONVERVATION OF FORESTS
Amrita Devi Bishnoi Wildlife Protection Award
CHIPKO MOVEMEWNT
JOINT FOREST MANAGEMENT
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WORD LIST BINGO
Chapter-1:
REPRODUCTION IN ANIMAL
Life span, reproduction, asexual reproduction, clone, binary fission, buds, zoospores, conidia, gemmules,
vegetative propagation, runner, rhizome, sucker, tuber, offset, bulb,vegetative propagules, nodes,sexual
reproduction, seasonal flowering, oestrous cycle, fertilization, gametogenesis, isogametes, heterogametes,
antherozoid, homothallic, monoecious, hetrothallic, dioecious, staminate,pistillate, unisexual, bisexual,
hermaphrodites, meiocytes, pollination
Syngamy, zygote, parthenogenesis, external fertilization, internal fertilization, embryogenesis, cell
differentiation, oviparous,viviparous,ovary, pericarp.
Chapter-2:SEXUAL REPRODUCTION IN FLOWERING PLANTS
Androecium, Gynoecium, stamen, filament, dithecous, microsporangia, pollen sacs,tapetum, sporogenous
tissue, microsporogenesis, microspore tetrad, pollen grains, exine, intine, germ pores, vegetative cell ,
generative
cell,monocarpellary
multicarpellary,syncarpous,
stigma
,
style,
ovary,placenta,megasporangia(ovule) funicle, hilum, integuments, micropyle, chalaza, nucellus, embryo
sac (female gametophyte), megasporogenesis, megaspore mother cell, megaspore, monosporic, egg
apparatus, synergids, antipodals, egg cells, filiform apparatus, polar nucleus, secondary nucleus,
pollination, autogamy, chasmogamous and cleistogamous flower, geitenogamy, xenogamy, outbreeding
devices, pollen- pistil interaction, artificial hybridization, emasculation, bagging, primary endos- perm
nucleus, triple fusion, endosperm , embryo, post fertilization events, scut- ellum, heart shaped embryo,
plumule, hypocotyle, epicotyle, plumule, radical, coleorrhiza, coleoptiles, albuminous/nonalbuminous
seed, perisperm, seed dormancy, pericarp,false/true /parthenocarpic fruit,apomixes, polyembryony.
Chapter-3:HUMAN REPRODUCTION
Insemination, implantation, testes, scrotum, seminiferous tubules, sertoli cells, interstitial cells of Leydig,
rete testis, vasa efferentia, epedidymis, vas deferens, urethral meatus, accessory reproductive glandsseminal vesicles, prostate, bulbourethral glands, ovaries, oviduct, uterus, cervix, vagina, mammary
glands, infundibulum, fimbriae, ampulla, isthmus, perimetrium, myometrium, endometrium,fallopian
tube,clitoris,lactiferous duct,spermatogenesis, spermatogonia, primary spermatocytes,secondary
spermatocytes, spermatids, spermatozoa, spermiogenesis/spermateleosis, spermiation ,acrosome, semen,
oogenesis, oogonia, primary oocyte, primary/secondary follicle, antrum, graffian follicle, zona pellucid,
ovulation,
polar
bodies,menstrual
cyclemenarche,corpus
luteum,
progesterone,
menopause,cleavage,morula, blastomeres,trophoblast cells, inner cellmsass, implantation, chorionioc villi,
h CG, h PL, estrogen, relaxin, umbilical cord, germ layers-ectoderm, mesoderm, endoderm, stem cells,
parturition, foetal ejection reflex, lactation, colostrums.
Chapter-4:REPRODUCTIVE HEALTH
Health,STDs,AIDS,Reproductive & child health care, amniocentesis, maternal mortality rate(MMR),
infant mortality rate(IMR), contraceptive,natural methods, periodic abstinence, withdrawal method/coitus
interruptus ,barrier methods, condoms, diaphragms, cervical caps, vaults, intra uterine devices(IUDs),
pills, sterilization, vasectomy,tubectomy,Medical Termination of Pregnancy(MTP), Infertility, Assisted
Reproductive technologies(ART),in-vitro fertilization(IFV), embryo transfer, test tube baby, zygote intra
210
fallopian transfer(ZIFT),intra uterine transfer(IUT), in-vivo fertilization, gamete intra fallopian
transfer(GIFT), Intra cytoplasmic sperm injection(ICSI), artificial insemination(AI), intra –uterine
insemination(IUI),Adolescence Reproductive and Sexual Health(ARSH), Reproductive Health
Chapter-5:PRINCIPLES OF INHERITANCE AND VARIATION
Inheritance, Fillial progeny, factors,traits, homologous chromosome,
gene, loci/locus, allele
homozygous,heterozygous ,phenotype, genotype, monohybrid cross, dominant , recessive, punnett
square,segregation, dihybrid cross, independent assortment,test cross,back cross, incomplete dominance,
co-dominance, chromosomal theory of inheritance,linkage, recombination,sex determination, autosomes,
sex chromosomes/allosomes,homogametic, heterogametic, mutation, chromosomal aberrations, frameshift mutation, pedigree analysis, consanguineous mating, Mendelian disorders, nondisjunction,
haemophilia, sickle cell anaemia, phenylketonurea, in born error of metabolism/metabolic
disorder,aneuploidy,polyploidy, syndrome, Down‘s syndrome, trisomy, Klinefeltor‘s syndrome,
gynaecomastia, Turner‘s syndrome, rudimentary/streak gonad.
Chapter-6:MOLECULAR BASIS OF INHERITANCE
Deoxyribonucleic Acid(DNA), ribonucleic Acid(RNA),nucleotide, nucleoside, nitrogenous bases(purine,
pyrimidine), sugar(pentose-deoxyribose/ribose),Adenine,Guanine, Thymine, Cytosin,Uracil, N-glycosidic linkage, Phosphodiester linkage, double helix, Chargaff‘s rule, anti parallel polarity, central dogma,
histones, octamer, nucleosome, chromatin, euchromatin, heterochromatin, nonhistone chromosomal
protein(NHC),Transformation(Griffith‘s experiment),
Transduction
(Hershey-Chase
experiment),
repli- cation,semiconservative replication,template DNA, Meselson-Stahl‘s experiment,replication fork,
helicases, topoisomerases, single stranded binding protein, primase,DNA polymerase, DNA
ligase,Okazaki fragments, continuous (leading)strand, discontinuous (lagging)strand, Transcription,
promoter,structural
genes/cistrons,terminator,DNA
dependent
RNApolymerase,coding
strand,
polycistronic,monocistronic,coding sequence(exon),non-coding sequence(intron), messengerRNA(m
RNA), transferRNA(t RNA),ribosomalRNA(r RNA), Initiation factor, termination factor, Eucaryotic transcription,
heterogenous
nuclear RNA(hn RNA),capping,tailing, splicing,Translation, genetic
code,codon, unambiguous, degenerate, universal, methionine/fMet, START/initiation codon(AUG),
STOP/NONSENSE CODON(UAA,UAG,UGA),frame shift (insertion/deletion) mutation, adapter
molecule, untranslated region,anti codon, aminoacylation of t RNA, release factor,regulation, gene
expression,operon, regulator, promoter,operator,lac-Operon,
B-galactosidase,permease,transacetylase,lactose,inducer,switch on/off, inducible system,negative regulation, Human GenomeProject
(HGP),GENOME, bioinformatics, DNA sequence, Expressed Sequence Tags(ESTs), Sequence
Annotation
Bacterial artificial chromosome(BAC),Yeast artificial chromosome(YAC),Single nucleotide
polymorphism(SNPs), DNA fingerprinting, DNA polymorphism, repetitive DNA, satellite DNA,
Variable Number Tandem Repeats(VNTRs),isolation of DNA, Electrophoresis, blotting, hybridization,
probe, autoradiography.
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Chapter-7:EVOLUTION
Evolution, Big bang, spontaneous generation, panspermia, Miller‘s experiment, HMS Beagle,
CharlesDarwin,fitness,AlfredWallace,fitness,naturalselection,evidences,morphology,anatomy,homologou
s organ, divergent evolution, analogous organ, convergent evolution, industrial melanism, adaptive
radiation, branching descent, saltation, stabilising selection, directional selection, disruptive selection,
gene migration, gene flow, genetic drift, mutation, genetic recombination, founder effect, geological
periods, Dryopithecus, Ramapithecus, Homo habilis, Homo erectus, Homo sapiens, Neanderthal man,
brain capacity.
Chapter-8:HUMAN HEALTH AND DISEASES
Health, disease ,infection, genetic disorders, life style disorders, infectious/ non-infectious, pathogen,
typhoid, widal test, pneumonia, common cold, malaria, Plasmodium spp. Anopheles sp. ,Haemozoin,
sporozoites, gametocytes,
amoebiasis,
ascariasis, elephantiasis/filariasis, Wuchereria bancrofti,
ringworms, personal hygiene, public hygiene, air borne disease, water borne disease, vector borne
diseases, biological control(Gambusia), Aedes, immunity, innate immunity, physical barrier,
physiological barrier, cellular barrier, cytokine barrier, acquired immunity, B lymphocytes,T ,lymph ocytes, antibody(Immunoglobuline), light chain, heavy chain, Humoral immune response, cell mediated
immunity, active immunity, passive immunity, colostrums, IgA, vaccination, immunization, allergies,
IgE, histamine, serotonin, auto immunity, lymphoid organs, bone marrow, thymus, mucosal associated
lymphoid tissue(MALT),Acquired Immuno Deficiency Syndrome (AIDS),retro virus, HIV, Enzyme
Linked Immuno Sorbent Assay(ELISA),Cancer, contact inhibition, benign tumor, malignant tumor,
neoplastic cells, metastatis, carcinogens, viral oncogenes ,proto oncogenes, radiotherapy, chemotherapy,
immunotherapy, a-interferon ,drugs, opioids, cannabinoids, cocaine, barbiturates, amphetamines, LSD,
hallucinogens, drug abuse, addiction, dependence, withdrawal syndrome, alcohol abuse , liver cirrhosis,
danger signs, peer pressure.
Chapter-9:STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION
Animal husbandry, dairy, poultry, animal breeding, inbreeding, out breeding, homozygosity, inbreeding
depression, out breeding, out crossing , cross breeding, interspecific hybridization, artificial insemination,
Multiple Embryo Transfer Technology(MOET), apiculture, fisheries, plant breeding, green revolution,
germplasm collection, cultivars, disease resistance, mutation breeding, insect pest
resistance,
biofortification, Single Cell Protein(SCP), tissue culture, explants, totipotency, micropropagation,
somaclones,meristem, somatic hybrids.
Chapter-10:MICROBES IN HUMAN WELFARE
Microbes, Lactic acid bacteria(LAB), Saccharomyces cerevisiae, fermentors, distillation, antibiotics,
bioactive molecules, streptokinase, clot buster, cyclosporine A, immunosuppressive agents, statins,
cholesterol lowering agents, sewage, primary treatment, primary sludge, flocs, Biochemical Oxygen
Demand(BOD), Activated sludge, anaerobic sludge digesters, biogas, Ganga action plan, Yamuna action
plan, methanogens, Bt cotton, Bacillus thuringiensis, baculoviruses, Trichoderma spp. Integrated Pest
Management(IPM), Biofertilisers, organic farming, mycorrhiza, cyanobacteria.
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Chapter-11:BIOTECHNOLOGY:PRINCIPLES AND PROCESSES
Biotechnology, genetic engineering, recombinant DNA, gene cloning, gene transfer, origin of replication,
plasmid, restriction enzymes, cloning, restriction endonuclease, recognition sequence, nucleases,
exonucleases, endonucleases, palindrome, sticky end ,blunt end, gel electrophoresis, elution, cloning
vectors, selectable markers, transformation, antibiotic resistance, insertional inactivation, tumor, Ti
plasmid, Agrobacterium tumifaciens, micro injection, biolistic/gene gun, lysozyme, cellulose, chitinase,
Polymerase Chain Reaction(PCR),denaturation, annealing, extension, thermostable DNApolymerase,
bioreactors, downsteam processing.
Chapter-12:BIOTECHNOLOGY AND ITS APPLICATION
Genetically Modified Organism(GMO), Bt cotton, insecticidal proteins, cry genes, pest resistant plants,
RNA interference(RNAi)/RNAsilencing, dsRNA, Genetically engineered insulin, gene therapy, ADA
deficiency , c DNA, Molecular diagnosis, transgenic animals, Bio ethics, Genetic Engineering Approval
Committee(GEAC), Bio piracy, Indian patent bill.
Chapter-13:ORGANISMS AND POPULATIONS
Organisms, population, communities, ecosystems, biomes, ecology, grassland,tundra, desert, coniferous
forest, temperate forest, tropical forest, abiotic features, temperature,stenothermal, eurithermal, water,
salinity, pH, light, soil, moisture,conformers, regulators, partial regulators,migration, suspension,
hibernation, aestivation,adaptation,altitude sickness, Allen,s rule
population attributes,age
pyramid(expanding, stable, declining),population density, natality, mortality, immigration, emigration,
exponential growth, logistic growth,mutualism, competition, predation, parasitism, commensalism,
amensalism.
Chapter-14:ECOSYSTEM
Terrestrial ecosystyem, aquatic ecosystem, stratification, productivity, Gross primary productivity
(GPP),Net primary productivity(NPP),S econdary productivity,decomposition, detritus, detritivores,
fragmentation, leaching, catabolism, humification, humus, mineralization, Photosynthetically active
radiaton(PAR),energy flow, producers,consumers,herbivores,carnivores,Grazing food chain(GFC),
Detritus Fo0od Chain(DFC), FOOD WEB, TROPHIC LEVEL, STANDING CROP, BIOMASS,
Ecological pyramids, upright pyramid, inverted pyramid, succession, pioneer, sere/seral stage, climax
community, Hydrarch succession, Xerarch succession, nutrient cycling , biogeochemical cycles,
ecosystem services.
Chapter-15:BIODIVERSITY AND CONSERVATION
Biodiversity, genetic diversity, species diversity, ecological/habitat diversity,mega diversity country, loss
of biodiversity,habitat loss, habitat fragmentation, over exploitation, alien/non native/invasive species,co
extinctions,narrowly utilitarian, broadly utilitarian,in situ conjservation, endemism, hotspots, sacred
groves, Ex situ conservation,Earth summit, sustainable development.
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Chapter-16:ENVIRONMENTAL ISSUES
Pollution, pollutants, Environmental Protection Act(EPA), Electrostatic Precipitator(ESP), Vehicular
pollution, Compressed Natural Gas(CNG), Euro ii, Bharatii, Air prevention and pollution control act,
noise pollution, decibel, water pollution, domestic sewage, dissolved oxygen(DO), Oxygen sag curve,
BIOCHEMICAL/BIOLOGICAL OXYGEN DEMAND(BOD), algal bloom, planktic, Bioaccumulation,
Biomagnificationj,solid wastes, municipal solid waste, sanitary landfills, plastic waste, e-wastes, agrochemicals, radioactive wastes, enhanced Greenhouse effect , Global warming, CFCs, stratospheric Ozone
depletion, deforestation,slash & burn agriculture, Jhum cultivation, deforestation, reforestation, chipco
movement, Joint Forest Management(JFM)
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Chapter : Hot Assignment
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3.
4.
If there was a point mutation in a DNA triplet that changed the code from T T G to T T A,
would that cause a problem with the resulting polypeptide chain? Explain Your answer.
If a different point mutation changed the DNA code from A C G to A C T, would that cause a
problem with the resulting polypeptide chain? Explain Your answer.
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Figure : Double Fertilization in a typical Angiosperm.
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