Beta-catenin is a protein that in humans and is encoded by the CTNNB1 gene. In Drosophila, the
homologous protein is called armadillo. Β-catenin is a subunit of the cadherin protein complex and has
been implicated as an integral component in the Wnt signaling pathway.
HMP SHUNT
The pentose phosphate pathway (also called Phosphogluconate Pathway, or Hexose Monophosphate
Shunt [HMP shunt]) is a process that serves to generate NADPH and the synthesis of pentose (5carbon) sugars.
Protein kinase A is a group of enzymes whose activity is dependent on the level of cyclic AMP in the
cell.PKA is also known as cAMP-dependent protein kinase. Protein kinase A has several functions in
the cell, including regulation of glycogen, sugar, and lipid metabolism. It is important in regulating cell
cycle, along with the protein Cyclin.
Chromosome puffs are diffuse uncoiled regions of the polygene chromosome that are sites
of RNA transcription. A Balbiani ring is a large chromosome puff.
Cyclic AMP or Cyclic Adenosine Monophosphate is the second messenger important in many
biological actions at the cellular level. It is the chemical messenger is generated in the cell membrane
from Adenosine triphosphate or ATP in response to a signal from the first messenger (Hormone).
cAMP is used for intracellular signal transduction in many organisms conveying the cAMP dependent
pathway.
Pinopodes are small, finger-like protrusions from the uterine endometrium. They appear between day
19 and day 21 of gestational age. This corresponds to a fertilization age of approximately 5 to 7 days,
which corresponds well with the time of implantation. They only persist for 2 to 3 days. The
development of them is enhanced by progesterone but inhibited by estrogens.
Polytene Chromosome
To increase cell volume, some specialized cells undergo repeated rounds of DNA
replication without cell division called Endomitosis, forming a giant Polytene chromosome.
Polytene chromosomes form when multiple rounds of replication produce many sister chromatids that
remain synapsed together.
Q Banding
Quinacrine mustard, an alkylating agent, was the first chemical to be used for chromosome banding.
T. Caspersson and his colleagues, who developed the technique, noticed that bright and dull
fluorescent bands appeared after chromosomes stained with quinacrine mustard were viewed under a
fluorescence microscope.
Central dogma of molecular biology
The central dogma of molecular biology was first enunciated by Francis Crick in 1958 and re-stated in
a Nature paper published in 1970.The central dogma deals with the detailed residue-by-residue
transfer of sequential information. It states that information cannot be transferred back from protein to
either protein or nucleic acid. In other words, 'once information gets into protein, it can't flow back to
nucleic acid.'
Chaperones
Chaperones are proteins that assist the non-covalent folding/unfolding and the assembly/disassembly
of other macromolecular structures, but do not occur in these structures when the latter are performing
their normal biological functions. The common perception that chaperones are primarily concerned
with protein folding is incorrect. The first protein to be called a chaperone assists the assembly of
nucleosomes from folded histones and DNA and such assembly chaperones, especially in the nucleus,
are concerned with the assembly of folded subunits into oligomeric structures.
Contig
A Contig (from contiguous) is a set of overlapping DNA segments derived from a single genetic
source. A Contig is also sometimes defined as the DNA sequence reconstructed from a set of
overlapping DNA segments.
DNA polymerase
A DNA polymerase is an enzyme that assists in DNA replication. Such enzymes catalyze the
polymerization of deoxyribonucleotides alongside a DNA strand, which they "read" and use as a
template. The newly-polymerized molecule is complementary to the template strand and identical to
the template's partner strand.
Initiatior (Inr) motif
The Initiatior (Inr) motif is a DNA transcription promoter that is similar in function to the Pribnow
box (for prokaryotes) or the TATA box (for eukaryotes). It has the consensus sequence
YYAN(T/A)YY,where Y stands for any pyrimidine (cytosine or thymine). Similarly to the TATA box,
the Inr motif facilitates the binding of Transcription Factor II D (TBP).
LINEs
Long interspersed nuclear elements are long DNA sequences (>5kb) that represent reverse-transcribed
RNA molecules originally transcribed by RNA polymerase II into mRNA (messenger RNA to be
translated into protein on ribosomes).
Pair-Rule Gene
Pair-rule gene is a type of gene involved in the development of the segmented embryos of insects.
Pair-rule genes are defined by the effect of a mutation in that gene, which causes the loss of the normal
developmental pattern in alternating segments.
Reverse transcription
Reverse transcription is the process of making a double stranded DNA (deoxyribonucleic acid)
molecule from a single stranded RNA (ribonucleic acid) template. It is called reverse transcription as it
acts in the opposite or reverse direction to transcription. This idea was very unpopular at first as it
contradicted the Central Dogma of Molecular Biology which states DNA is transcribed into RNA
which is translated into proteins. However, in 1970 when the scientists Howard Temin and David
Baltimore both independently discovered the enzyme responsible for reverse transcription, named
reverse transcriptase, the possibility that genetic information could be passed on in this manner was
finally accepted.
Ribozyme
A Ribozyme is an RNA molecule that catalyzes a chemical reaction. Many natural ribozyme catalyze
either the hydrolysis of one of their own phosphodiester bonds, or the hydrolysis of bonds in other
RNAs, but they have also been found to catalyze the aminotransferase activity of the ribosome.
Sigma factor
A sigma factor (σ factor) is a prokaryotic transcription initiation factor that enables specific binding of
RNA polymerase to gene promoters. Different sigma factors are activated in response to different
environmental conditions. Every molecule of RNA polymerase contains exactly one sigma factor
subunit, which in the model bacterium Escherichia coli is one of those listed below. E. coli has at least
eight sigma factors; the number of sigma factors varies between bacterial species. Sigma factors are
distinguished by their characteristic molecular weights. For example, σ70 refers to the sigma factor
with a molecular weight of 70 kDa.
SINEs
Short interspersed nuclear elements are short DNA sequences (<500 bases) that represent reversetranscribed RNA molecules originally transcribed by RNA polymerase III into tRNA, rRNA, and other
small nuclear RNAs. SINEs do not encode a functional reverse transcriptase protein and rely on other
mobile elements for transposition.
TATA box
The TATA box (also called Goldberg-Hogness box) is a DNA sequence (cis-regulatory element) found
in the promoter region of most genes in eukaryotes and Archaea. Considered to be the core promoter
sequence, it is the binding site of either transcription factors or histones (the binding of a transcription
factor blocks the binding of a histone and vice versa) and is involved in the process of transcription by
RNA polymerase.
The Pribnow box
The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six
nucleotides (thymine-adenine-thymine-etc.) that is an essential part of a promoter site on DNA for
transcription to occur in bacteria. It is an idealized or consensus sequence - that is, it shows the most
frequently occurring base at each position in a large number of promoters analyzed; individual
promoters often vary from the consensus at one or more positions. It is also commonly called the -10
sequence, because it is centered roughly 10 base pairs upstream from the site of initiation of
transcription.
Cell signaling
Cell signaling is part of a complex system of communication that governs basic cellular activities and
coordinates cell actions. The ability of cells to perceive and correctly respond to their
microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue
homeostasis. Errors in cellular information processing are responsible for diseases such as cancer,
autoimmunity, and diabetes. By understanding cell signaling, diseases may be treated effectively and,
theoretically, artificial tissues may be yielded.
Cell surface Receptors
A Receptor is a protein molecule, embedded in either the plasma membrane or the cytoplasm of a
cell, to which one or more specific kinds of signaling molecules may attach. A molecule which binds
to a receptor is called a ligand, and may be a peptide or other small molecule, such as
a neurotransmitter, a hormone, a pharmaceutical drug, or a toxin. Each kind of receptor can bind only
certain ligand shapes. Each cell typically has many receptors, of many different kinds.
Endocrine Disruptors
Endocrine disruptors are chemical substances that act on the endocrine system and disrupt its
functions. The term Endocrine disruptor was introduced in the Wingspread Conference Centre;
Wisconsin in 1991.The work of Theo Colborn showed that the environmental chemicals disturbed the
development of endocrine system. Endocrine disruption refers to the fact that there is negative
interference or permanent adverse consequences beyond the range of everyday fluctuations of hormone
levels.
METAPLASIA
Metaplasia (Greek: "change in form") is the reversible replacement of one differentiated cell type with
another mature differentiated cell type. The change from one type of cell to another is generally caused
by some sort of abnormal stimulus. In simplistic terms, it is as if the original cells are not robust
enough to withstand the new environment, and so they change into another type more suited to the new
environment. If the stimulus that caused Metaplasia is removed or ceases, tissues return to their normal
pattern of differentiation. Metaplasia is not synonymous with dysplasia and is not considered
carcinogenesis. It is also contrasted with heteroplasia, which is the abnormal growth of cytologic and
histologic elements without a stimulus.
PYROGENS
Paracetamol is the safest drug used to control temperature. It is called as Antipyretic. When there is infection
in the body, the WBC produces chemical called Pyrogens. The pyrogens are responsible for fever. Paracetamol
inhibits the production of pyrogens and reduce body temperature. Paracetamol is the diethylated product of
the active metabolite of Phenacetin which is now banned. Paracetamol is a para-amino phenol derivative
which is N-acetyl-p-aminophenol.
Membrane Receptor Structure
The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells) that is, in
general, responsible for recognizing antigens bound to major histocompatibility complex (MHC)
molecules.
It is a heterodimer consisting of an alpha and beta chain in 95% of T cells, whereas 5% of T cells have
TCRs consisting of gamma and delta chains. Engagement of the TCR with antigen and MHC results in
activation of its T lymphocyte through a series of biochemical events mediated by associated enzymes,
co-receptors, specialized accessory molecules and activated or released transcription factors.
Secondary messenger system
A secondary messenger system (also known as a second messenger system) is a method of cellular
signaling, whereby a diffusable signaling molecule is rapidly generated/released which can then go on
to activate effector proteins within the cell to exert a cellular response. Secondary messengers are a
component of signal transduction cascades.
Assisted Reproductive Technology -ART
Assisted reproductive technology is the methods used to achieve pregnancy by artificial or partially
artificial means. It is reproductive technology used primarily in infertility treatments. ART is also used
in couples who are discordant for certain communicable diseases, i.e. AIDS, to reduce the risk of
infection when a pregnancy is desired. The term also includes any reproductive technique involving a
third party e.g. a sperm donor. There is yet no strict definition of the term. Usage of the ART mainly
belongs in the field of reproductive endocrinology and infertility.
Bio-Electric Stimulation Therapy – BEST
It is also known as Micro Current Electrotherapy or MET. It is a specific electro therapy that gives
small current into the body. The current is less than one milli ampere. BEST mimics the electrical
stimulations of cells by the nerves. This increases the physiology of the cells. BEST has a positive
effect on fatigue and chronic pain. BEST boosts energy levels of the cells and restores the homeostasis
of the cells by increasing the production of ATP, Transmembrane transport, stimulation of fibroblasts
etc.
BLAST- Basic Local Alignment Search Tool
The BLAST is used to infer functional and evolutionary relationships between sequences as well as
help identify members of gene families. The FASTA programs find regions of local or global
similarity between Protein or DNA sequences, either by searching Protein or DNA databases, or by
identifying local duplications within a sequence.
CHORDIN
Second organizer protein isolated from the clones of cDNA whose mRNAs were present in dorsalised,
but not in ventralized embryo. It .is a polypeptide that dorsalizes the developing embryo by binding
ventralizing TGFβ proteins such as Bone morphogenetic proteins. It may also play a role in
organogenesis. There are five named isoforms of this protein that are produced by alternative splicing.
Cryopreservation
Cryopreservation is a process where cells or whole tissues are preserved by cooling to low sub-zero
temperatures, such as (typically) 77 K or −196 °C (the boiling point of liquid nitrogen). At these low
temperatures, any biological activity, including the biochemical reactions that would lead to cell death,
is effectively stopped. However, when vitrification solutions are not used, the cells being preserved are
often damaged due to freezing during the approach to low temperatures or warming to room
temperature.
Decidualization
Decasualization succeeds pre decidualization if pregnancy occurs. This is an expansion of it, further
developing the uterine glands, the zona compacta and the epithelium of decidual cells lining it. The
decidual cells become filled with lipids and glycogen and take the polyhedral shape characteristic for
decidual cells.
Fluorescence in Situ Hybridization – FISH
Fluorescence in situ hybridization (FISH) is the molecular cytogenetic technique that allows
cytogeneticists to analyze chromosome resolution at the DNA or gene level. FISH can be performed on
dividing (metaphase) and non-dividing (interphase) cells to identify numerical and structural
abnormalities resulting from genetic disorders.
GIFT: Gamete Intra-Fallopian Transfer
GIFT involves placement of unfertilized eggs from the woman and her partner's sperm in the fallopian
tubes of the woman with laparoscopy. GIFT can be used as an effective treatment for infertility of all
causes except for women with infertility caused by tubal blockage or significant tubal damage or an
anatomic problem with the uterus, such as severe intrauterine adhesions. It also should not be used for
any significant male factor infertility cases.
Insitu Hybridization
In situ hybridization (ISH) is a type of hybridization that uses a labeled complementary
DNA or RNA strand (i.e., probe) to localize a specific DNA or RNA sequence in a portion or section
of tissue (in situ), or, if the tissue is small enough (e.g. plant seeds, Drosophila embryos), in the entire
tissue (whole mount ISH). DNA ISH can be used to determine the structure of chromosomes.
Fluorescent DNA ISH (FISH) can, for example, be used in medical diagnostics to assess
chromosomal integrity. RNA ISH (hybridization histochemistry) is used to measure and localize
mRNAs and other transcripts within tissue sections or whole mounts.
MAJOR HISTOCOMPATIBILITY COMPLEX
Location and functions of MHC
A viral infected cell will express small fragments of viral protein on its surface to recognize by
cytotoxic T cells. The antigen fragments are presented on the surface of the cell by a specialized group
of molecules called MHC proteins. These are encoded in a set of genes called Major
Histocompatibility Complex (MHC). The genes are located in the 5Th chromosome Major
histocompatibility complex (MHC): Originally recognized as antigens responsible for graft rejection in
incompatible hosts after transplantation. These are molecules that bind with processed antigens and are
displayed on the surface of cells. MHC class I molecules are displayed on non-immune cells and MHC
class II on antigen-presenting cells.
Nidation
The organic process by which the developing blasocyst attaches to the uterine lining. There are many
conditions that must be satisfied in order for a successful implantation to take place. There is only a
specific period of time during which implantation is possible; this is the "implantation window". A
reason for this window is that if implantation does not occur at a certain time, then it signifies that
something is wrong. And when there is a risk that something is wrong, there will most likely be
a miscarriage rather than the continued gestation of a malformed fetus.
Nieuwkoop Center
Nieuwkoop Center is the Primary Organizer forming centre seen in the developing egg of some
Amphibians. In Xenopus, the Nieuwkoop Center is the dorsal- and vegetal-most region. It gives rise to
the Primary Organizer called Spemann-Mangold Organizer which is the region known as
the dorsal lip of the blastopore (DLB). Spemann and Mangold’s experiments found that the DLB
dorsalizes surrounding tissue, thus forming the dorsal-ventral axis. In addition to dorsalizing
surrounding tissue, the Primary Organizer fates overlying ectoderm as neural plate tissue; and is
determined to be notochord tissue.
NOGGIN
First soluble organizer molecule isolated in 1992 by Smith and Harland. Noggin is a polypeptide that
binds to members of the TGF-β super family of proteins. It is a Bone morphogenetic protein inhibitor.
Noggin plays a key role in neurulation by inhibiting BMP4, along with other morphogens such as
chordin and follistatin and inducing the formation of the neural plate. It plays a crucial role in bone
development, by regulating the functions of BMP's. During the morphogenisis of organs such as the
lungs, teeth and hair follicles, noggin helps to produce Lef1. Mouse knockout experiments show that
noggin plays a role in neural tube fusion and joint formation.
Physical Gene Mapping
In physical mapping, the DNA is cut by a restriction enzyme. Once cut, the DNA fragments are
separated by electrophoresis. The resulting pattern of DNA migration (i.e., its genetic fingerprint) is
used to identify what stretch of DNA is in the clone. By analyzing the fingerprints, Contigs are
assembled by automated or manual means into overlapping DNA stretches. Now a good choice of
clones can be made to efficiently sequence the clones to determine the DNA sequence of the organism
under study.
Pinopodes
Pinopodes are small, finger-like protrusions from the uterine endometrium. They appear between day
19 and day 21 of gestational age. This corresponds to a fertilization age of approximately 5 to 7 days,
which corresponds well with the time of implantation. They only persist for 2 to 3 days. The
development of them is enhanced by progesterone but inhibited by estrogens.
Snuppy
Snuppy (born April 24, 2005) is the world's first cloned dog. This Afghan Hound clone was created by
Hwang Woo-Suk and his team of scientists at Seoul National University (SNU) in South Korea. The
name "Snuppy" is a combination of "SNU" and "puppy."The researchers transferred 1,095 dog
embryos into 123 females, inducing three pregnancies. One fetus miscarried, and one clone died of
pneumonia after three weeks. A Labrador Retriever carried the third embryo to term. The team
announced their success in cloning in August of 2005.
TISSUE GRAFTING
Autografts Any tissue transferred from one site to another in the same individual (iliac bone from the
pelvis is commonly used to supplement the fusion mass). Tissue taken from one part of an individual
organism's body and then moved or transplanted to another location within that same organism.
Rejection is rarely (if ever) a problem since the donor and recipient are the same individual. Skin
transplants are a common example.
Allograft Graft of a piece of tissue or organ from one individual to another of the same species
Homograft: tissue or organ transplanted from a donor of the same species but different genetic
makeup; recipient's immune system must be suppressed to prevent rejection of the graft
Isografts A graft of tissue between genetically identical individuals
Xenografts -zen´o-graft. A graft of tissue transplanted between animals of different species. Called
also heterograft, heterologous graft, and heteroplastic graft. Xenotransplantation is the transplantation
of living cells, tissues or organs from one species to another such as from pigs to humans. (See
Medical grafting.) Such cells, tissues or organs are called Xenografts (xenotransplants). The term allo
transplantation refers to a same-species transplant.
Graft retention – methods - To prevent tissue rejection drugs called ‘Immunosuppressants” are
administered after the organ transplantation. The most commonly used drugs are Antimetabolites,
Alkylating agents, Toxic antibodies etc. Radiation, Cyclosporin FK 506, Antilymphocyte globulins,
Adrenal corticoids, Azothioprine etc are also used as Immunosuppressants. These drugs hinder the
development of T lymphocytes.
Graft rejection – methods- Tissue rejection is due to cell mediated immune system of T cells of the
recipient consider the transplanted organ as ‘Non self’. The process of rejection starts after 10-14 days
of transplantation. This is indicated by the accumulation of T cells in the blood vessels of the
transplanted organ. This prevents normal blood flow to the organ leading to its rejection. The MHC
also stimulates the production
ZIFT
ZIFT: Stands for zygote intrafallopian transfer, a method used to treat infertility in which an egg
fertilized in vitro (outside the body) is placed into a woman's fallopian tube. This technique is one used
to overcome infertility, the inability of couples to produce offspring on their own.
EPITOPES AND HAPTENS
Epitope – A single antigenic determinant. Functionally it is the portion of an antigen which combines
with the antibody .Antibody binds to a particular part of the antigen called epitope. A particular antigen
has different epitopes. Antibodies are specific for the epitope rather than the whole complex
Hapten – A single molecule which act as an epitope but is incapable by itself of eliciting an antibody
response. Become Immunogenic only if bound to a protein carrier. Used to produce immune response,
production of polyclonal and monoclonal antibodies
MALNUTRITION DISEASES
Deficiency of one or more nutrients in the food for prolonged period leads to the appearance of
diseases called malnutrition diseases. Kwashiorkor is a malnutrition disease caused by the deficiency
of Proteins. It is characterized by stunted growth, mental retardation, thin legs, protruded belly etc.
Marasmus is caused by the deficiency of Proteins and Calorie. It is characterized by flabby body,
elevated ribs, weakness etc. Excess intake of food leads to Obesity characterized by overweight.
Hypercholesterolemia is the high cholesterol level (150 – 250 mg / 100 ml blood) in the blood. It is
due to excess intake of fatty food materials. Excess cholesterol leads to Arteriosclerosis, High blood
pressure etc.
PACINIAN CORPUSCLES
Pacinian corpuscles are present in the skin to detect touch sensation. It has very large receptive area
that receives vibratory sensation. It is onion like in appearance. Other receptors for pressure detection
are Meissner’s corpuscles for Speed of stimulus application, Merkel’s for location of stimulus and
Ruffni’s corpuscles for magnitude and duration of stimuli.
PROLACTIN
Prolactin is the only pituitary hormone which is directly inhibited by the Hypothalamus. Other
hormones receive positive response through Releasing Factors-RF. Prolactin Inhibiting Factor – PIF –
which is chemically Dopamine is produced from the hypothalamus. It inhibits the Prolactin. When the
brain is transected, due to the absence of PIF, Prolactin amount increases. But other hormones like
ACTH, GH, TH etc decrease.
Gap Gene
Gap gene is a type of gene involved in the development of the segmented embryos of
some arthropods. Gap genes are defined by the effect of a mutation in that gene, which causes the loss
of contiguous body segments, resembling a gap in the normal body plan. Each gap gene, therefore, is
necessary for the development of a section of the organism.
Homeotic genes
Genes that affect embryo development by specifying the character of a body segment. The classic
example is Antennapedia, a gene that, when mutated, causes a fruitfly to grow a leg in place of
antenna. Homeotic genes are homeobox genes that are responsible for segment identity in metazoan
organisms. Inappropriate expression of Homeotic genes will, in general, transform parts of the body
into structures appropriate to other positions. An example would be the Antennapedia mutant of the
fruit fly Drosophila, in which legs are found sprouting where antennae would normally be. Localized
expression of Homeotic genes is controlled by upstream maternal proteins, gap genes, and pair rule
genes in the developmental cascade.
Lamp brush chromosome
Lamp brush chromosome is a kind of Giant or Polytene chromosome found in the developing
Oocytes of some Animals. It was discovered by Ruckert in 1892. The Lamp brush chromosome
contains lateral loops and appears like a brush. Hence the name lamp brush chromosomes. It is found
in the Oocytes of Sagitta, Sepia, Echinaster (Echinoderm), insects, sharks, amphibians, reptiles, and
birds. Each lamp brush chromosome consists of a main axis and many lateral loops. The main axis of
each chromosome is formed of 4 chromatids. The main axis contains a series of thickenings called
chromomere. From each chromomere a pair of lateral loops one on each side. Each loop has an axial
fibre. The axial fibre is the continuation of the chromonema of the main axis. Hence it contains DNA.
MITOCHONDIAL GENETICS
Mitochondrial genetics is the study of the genetics of the DNA contained in mitochondria.
Mitochondria are small structures in cells that generate energy for the cell to use, and are hence
referred to as the "powerhouses" of the cell.
Mitochondrial DNA (mtDNA) is not transmitted through nuclear DNA (nDNA), and in most
multicellular organisms, virtually all mitochondria are inherited from the mother's ovum, as it is
unusual for sperm cells to contribute mitochondria when fertilising ova.
Mitochondrial inheritance is therefore non-Mendelian, as Mendelian inheritance presumes that half the
genetic material of a fertilized egg (zygote) derives from each parent.
Restriction Endonuclease
A restriction enzyme (or restriction Endonuclease) is an enzyme that cuts double-stranded or single
stranded DNA at specific recognition nucleotide sequences known as restriction sites. Such enzymes,
found in bacteria and archaea, are thought to have evolved to provide a defense mechanism against
invading viruses. Inside a bacterial host, the restriction enzymes selectively cut up foreign DNA in a
process called restriction; host DNA is methylated by a modification enzyme (a methylase) to protect
it from the restriction enzyme’s activity. Collectively, these two processes form the restriction
modification system. To cut the DNA, a restriction enzyme makes two incisions, once through each
sugar-phosphate backbone (i.e. each strand) of the DNA double helix.
Retrotransposons
Retrotransposons (also called transposons via RNA intermediates) are genetic elements that can
amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic
organisms. They are a subclass of transposon. They are particularly abundant in plants, where they are
often a principal component of nuclear DNA. In maize, 49-78% of the genome is made up of
retrotransposons. In wheat, about 90% of the genome consists of repeated sequences and 68% of
transposable elements. In mammals, almost half the genome (45% to 48%) comprises transposons or
remnants of transposons. Around 42% of the human genome is made up of retrotransposons while
DNA transposons account for about 2-3%.
Gene Frequency
Gene frequency or Allele frequency is the proportion of all copies of a gene that is made up of a
particular gene variant (allele). In other words, it is the number of copies of a particular allele divided
by the number of copies of all alleles at the genetic place (locus) in a population. It can be expressed
for example as a percentage. In population genetics, allele frequencies are used to depict the amount
of genetic diversity at the individual, population, and species level. It is also the relative proportion of
all alleles of a gene that are of a designed type.
Gene Pool
A gene pool is the complete set of unique alleles in a species or population. A large gene pool
indicates extensive genetic diversity, which is associated with robust populations that can survive bouts
of intense selection. Meanwhile, low genetic diversity can cause reduced biological fitness and an
increased chance of extinction. When all individuals in a population are identical with regard to a
particular phenotypic trait, the population is said to be monomorphic. When the individuals show
several variants of a particular trait they are said to be polymorphic.
Genetic polymorphism
Genetic polymorphism is the simultaneous occurrence in the same locality of two or more
discontinuous forms in such proportions that the rarest of them cannot be maintained just by recurrent
mutation.Genetic polymorphism is actively and steadily maintained in populations by natural selection,
in contrast to transient polymorphisms where a form is progressively replaced by another. By
definition, genetic polymorphism relates to a balance or equilibrium between morphs.
Founder Effect
The founder effect refers to the loss of genetic variation when a new colony is established by a very
small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1952,
using existing theoretical work by those such as Sewall Wright. As a result of the loss of genetic
variation, the new population may be distinctively different, both genetically and phenotypically, from
the parent population from which it is derived. In extreme cases, the founder effect is thought to lead to
the speciation and subsequent evolution of new species.
Genetic Drift
The genetic drift or allelic drift is the evolutionary process of change in the allele frequencies (or
gene frequencies) of a population from one generation to the next due to the phenomena of probability
in which purely chance events determine which alleles (variants of a gene) within a reproductive
population will be carried forward while others disappear. Especially in the case of small populations,
the statistical effect of sampling error during random sampling of certain alleles from the overall
population may result in an allele, and the biological traits that it confers, to become more common or
rare over successive generations, and result in evolutionary change over time.
The concept of Genetic drift was first introduced by Sewall Wright in the 1920s, and is now held to be
one of the primary mechanisms of biological evolution. It is distinct from natural selection, a nonrandom evolutionary selection process in which the tendency of alleles to become more or less
widespread in a population over time is due to the alleles' effects on adaptive and reproductive success.
Gene Pool
The gene pool is the complete set of unique alleles in a species or population. A large gene pool
indicates extensive genetic diversity, which is associated with robust populations that can survive.
Meanwhile, low genetic diversity can cause reduced biological fitness and an increased chance of
extinction. When all individuals in a population are identical with regard to a particular phenotypic
trait they are known as Monomorphic.
Hardy-Weinberg Principle
Hardy-Weinberg principle states that when no evolution occurs in a population the allele and genotype
frequencies do not change from one generation to the next. No evolution refers to no mutation, no gene
flow, no natural selection, and no genetic drift. To be in equilibrium two more assumptions need to be
made that random mating occurs and there are discrete, non-overlapping generations.
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F.
Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or
'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages.Whether
genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion.
There are four geographic modes of speciation in nature, based on the extent to which speciating
populations are geographically isolated from one another: allopatric, peripatric, parapatric, and
sympatric. Speciation may also be induced artificially, through animal husbandry or laboratory
experiments. Observed examples of each kind of speciation are provided throughout.
Chromosome Banding
It is the cytological technique in which the metaphase chromosome is stained using appropriate stains
to see the banding pattern of the chromosome. Chromosome band is the transverse band produced
on the chromosomes by differential staining techniques. Depending on the particular staining
technique, the bands are alternating light and dark or fluorescent and non fluorescent.
GenBank
The GenBank sequence database is the open access database. It is the annotated collection of all
publicly available nucleotide sequences and their protein translations. The GenBank is produced at
National Center for Biotechnology Information-NCBI- as part of the International Nucleotide
Sequence Database Collaboration. GenBank receive sequences produced in laboratories throughout the
world. GenBank contains the data of over 65 billion nucleotide bases.
Human Cytome project
Cytomes are the cellular systems, subsystems, and functional components of the body. The cytome is
the collection of the complex and dynamic cellular processes (structure and function) underlying
physiological processes. It describes the structural and functional heterogeneity of the cellular diversity
of an organism. The study of Cytome is called Cytomics.
Molecular Cloning
Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple
copies of it in vitro. Cloning is frequently employed to amplify DNA fragments containing genes, but
it can be used to amplify any DNA sequence such as promoters, non-coding sequences, chemically
synthesized oligonucleotide and randomly fragmented DNA. Cloning is used in a wide array of
biological experiments and technological applications such as large scale protein production.
Electroencephalography (EEG)
EEG is the recording of electrical activity along the scalp produced by the firing of neurons within the
brain. In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity
over a short period of time, usually 20-40 minutes, as recorded from multiple electrodes placed on the
scalp. In neurology, the main diagnostic application of EEG is in the case of epilepsy, as epileptic
activity can create clear abnormalities on a standard EEG study. A secondary clinical use of EEG is in
the diagnosis of coma and encephalopathies. EEG used to be a first-line method for the diagnosis of
tumors, stroke and other focal brain disorders, but this use has decreased with the advent of anatomical
imaging techniques such as MRI and CT.
Electroporation
Electroporation is the artificial means of DNA transfer into the cells using an electrical field. It is
defined as the use of electrical field to reversibly form micropores in the cell membrane. It is relatively
new, simple and rapid technique to introduce DNA in a wide variety of cells. This technique is based
on the original observation of Zimmermann in 1983 that high current pulses can induce cell
membranes to fuse.
ESEM
The invention of Environmental SEM (ESEM) during 1980s allowed samples to be observed in lowpressure gaseous environments of 1-50 Torr and high relative humidity. This was made possible by the
development of a secondary-electron detector capable of operating in the presence of water vapour and
by the use of pressure-limiting apertures with differential pumping in the path of the electron beam to
separate the vacuum regions around the gun and lenses from the sample chamber. The first commercial
ESEMs were produced by the ElectroScan Corporation in USA in 1988.
ESEM uses a proprietary Environmental Secondary Detector (ESD) which can function in non-vacuum
environment instead of Everhart-Thornley (ET) detector used in SEM. The ESD uses the principle of
gas ionization. By applying a positive potential of a few hundred volts to the detector, the secondary
electron emitted by the sample when interacts with electron beam is attracted to detector. As the
electrons accelerate in the detector field, they collide with gas molecules. The resulting ionizations
create additional electrons, amplifying original secondary electron signal, and positive ions. The
detector collects secondary electron signal and passes it directly to an electron amplifier. In
nonconductive samples the positive ions created in gas ionization process are attracted to the sample
surface and they effectively suppress charging artifacts.
Functional MRI or functional Magnetic Resonance Imaging (fMRI) is a type of specialized MRI
scan. It measures the haemodynamic response related to neural activity in the brain or spinal cord of
humans or other animals. It is one of the most recently developed forms of neuroimaging. Since the
early 1990s, fMRI has come to dominate the brain mapping field due to its low invasiveness, lack of
radiation exposure, and relatively wide availability.
GENE MAPPING
Gene mapping refers to one of two different ways of definitively locating the gene on a chromosome.
The first type of gene mapping is also called genetic mapping. Genetic mapping refers to the use of
linkage analysis to determine how two genes on a chromosome relate in their positions. Physical
mapping, the other type of gene mapping, locates genes by their absolute positions on a
chromosome using any technique available. Once a gene is located, it can be cloned, its DNA
sequence determined, and its molecular product studied.
Light Microscopy
Leeuwenhoek developed the first powerful microscope
Chromatic aberration
Chromatic aberration is caused by a lens having a different refractive index for different wavelengths
of light (the dispersion of the lens).Longitudinal and lateral chromatic aberration of a lens is seen as
"fringes" of color around the image, because each color in the optical spectrum cannot be focused at a
single common point on the optical axis.
Numerical aperture
Numerical aperture (NA) is the light gathering ability of the Lens
The numerical aperture of an optical system such as an objective lens is defined by
where n is the index of refraction of the medium in which the lens is working (1.0 for air, 1.33 for pure
water, and up to 1.56 for oils)
θ is the half-angle of the maximum cone of light that can enter or exit the lens.
In microscopy, NA is important because it indicates the resolving power of a lens.
The size of the finest detail that can be resolved is proportional to λ/NA, where λ is the wavelength of
the light.
A lens with a larger numerical aperture will be able to visualize finer details than a lens with a smaller
numerical aperture. Lenses with larger numerical apertures also collect more light and will generally
provide a brighter image.
NA of the condenser lens control resolution of the objective
Lm = λ / NA of objective + NA of condenser
NA of oil immersion objective is 1 to 1.35
Lm = 0.61 λ / 1.3 = 0.5 λ
In air NA is less than 1.
The practical way to increase NA is to increase refractive index of the medium
Refractive index of Air is 1. Optical lenses less than 1.6. Oil 1.4
Resolution
Optical resolution describes the ability of an imaging system to resolve detail in the object that is being
imaged. Lens resolution is the ability of a lens to resolve detail is usually determined by the quality of
the lens but is ultimately limited by diffraction.
A measure of the resolving power of a lens is given by its numerical aperture, NA:
where λ is the wavelength of light. From this it is clear that a good resolution (small δ) is connected
with a high numerical aperture.
The ability to distinguish two close points as distinct points is called Resolving power or Limit of
resolution
Limit of resolution of light microscope Lm = 0.16 / NA
Limit of resolution of unaided human eye is 100 micrometer
Limit of resolution of optical microscope is 0.25 micrometer
Limit of resolution is inversely proportional to the wavelength of light.
Lm is determined using the Abbe equation Lm = 0.61λ / NA
Lm is the limit of resolution; λ is the wavelength of light and NA numerical aperture
Lm can be improved by
1. Using shorter wavelength of light
2. Increasing refractive index of the medium (n) or Sine of semi angle of light (Sin )
Sin
is the sine of angle of light passing into the objective from the specimen
It can be higher than 1. Because Sin 90 degree is equal to 1, while Sine 70 degree = 0.94
For best objective lens semi angle is 70 degree
Resolution of a microscope is roughly ½ the wavelength of the illumination light
Average wavelength of light is 500 – 600 nm which gives a resolution of 250 – 300 nm or 0.25 – 0.3
micrometer.
The visible light of shortest wavelength is around 426 nm giving an Lm of 200 nm or 0.2 micrometer
So superior microscopes uses blue light or blue filters
Magnification
Enlargement or Ratio of size of an object obtained under the microscope and its actual size seen with
the naked eye
Magnification equals to the magnification of the objective lens multiplied by the magnification of the
eye piece
Working Distance
Distance between the object (or cover glass) and the surface of the front lens of objective
Low power objectives (10X, 45X) have large working distance and smaller NA
High power objectives (100X) have short working distance and large NA
Magnification is also a number describing by which factor an object was magnified. When this number
is less than one it refers to a reduction in size, sometimes called Minification.
Depth of Field
In optics, particularly as it relates to film and photography, the depth of field (DOF) is the portion of a
scene that appears sharp in the image.
The DOF is determined by the subject distance the lens focal length, and the lens f-number (relative
aperture)
Real Image
A real image is a representation of an actual object (source) formed by rays of light passing through the
image. If a screen is placed in the plane of a real image the image will generally become visible.
Virtual Image
A virtual image is an image in which the outgoing rays from a point on the object never actually
intersect at a point.
Wavelength
Wavelength is the distance between repeating units of a propagating wave of a given frequency.
It is commonly designated by the Greek letter lambda (λ). Examples of wave-like phenomena are light,
water waves, and sound waves.
The wavelength is related to the frequency by the formula: wavelength = wave speed / frequency.
Wavelength is therefore inversely proportional to frequency.
Higher frequencies have shorter wavelengths. Lower frequencies have longer wavelengths, assuming
the speed of the wave is the same.
Magnetic resonance imaging (MRI),
Magnetic resonance imaging (MRI), or nuclear magnetic resonance imaging (NMRI), is primarily a
medical imaging technique most commonly used in radiology to visualize the structure and function of
the body. It provides detailed images of the body in any plane. MRI provides much greater contrast
between the different soft tissues of the body than computed tomography (CT) does, making it
especially useful in neurological (brain), musculoskeletal, cardiovascular, and oncological (cancer)
imaging. Unlike CT, it uses no ionizing radiation, but uses a powerful magnetic field to align the
nuclear magnetization of (usually) hydrogen atoms in water in the body. Radiofrequency fields are
used to systematically alter the alignment of this magnetization, causing the hydrogen nuclei to
produce a rotating magnetic field detectable by the scanner. This signal can be manipulated by
additional magnetic fields to build up enough information to construct an image of the body.
MEDICAL INSTRUMENTS
Non Invasive Techniques
body
Einthoven
Techniques and instruments which are free from risk of injury to the
Father of Electrocardiography
Echocardiography
Also called Sonography – Used to image Aorta, Heart valves, Heart wall
etc. It is also used to record blood flow velocity and blood turbulence
Vector cardiography
To analyze Q wave and Intra ventricular conduction abnormalities
SQUID
Super conducting Quantum
encephalograph.
Interference
Device.
Eg.
Magneto
MET
Magneto Encephalographic Technique and SQUID are used to give
information about the health of various parts of the brain. It can be used
to study weaker magnetic fields for the brain.
Auto Analyzer
Fully computerized, automatic instrument which can analyze
qualitatively and quantitatively various bio chemicals present in body
fluids.
Tomography
Technique of development of three dimensional impression of internal
organs imaging of different layers. Tomography can indicate cysts,
tubercular foci , calculi , cancers etc.
CT Scanning
Uses short X rays for radiographic imaging of internal organs. CT
scanning employs more than 30,000, 2-4 mm beams of X-rays. It uses
low level X-rays so that radiation damage is little. CT scanning is used to
diagnose parts like abdomen, chest, spinal cord, brain, tumors, oedema
etc. It is commonly used to investigate the brain after a Stroke.
CAT
Computerized Axial Tomography. Uses X- rays to study internal parts in
the skull. CAT is now replaced by CT scanning.
PET
Positron Emission Tomography. Used to measure metabolic rate,
regional blood volume, blood flow , area of abnormalities. Special
centers of the brain, like colour processing in visual cortex of humans
can be detected by PET.PET uses positron emitting radio isotopes like
Carbon eleven.
MRI
Magnetic Resonance Imaging. Uses strong magnetic field for generating
resonance and low radio frequency in protons present in the body. The
most common proton is the H1 nuclei present in water molecules. MRI is
superior than CT because
1. It uses non ionizing radiations
2. It gives 2 or 3D pictures.
3. Image is obtained from any plane.
4. Provides better information about tumors and infections.
MRI scanning cannot be performed in patients carrying Ferro magnetic
devices like artificial pace makers, metal cardiac valves etc because the
MRI magnets will interfere with this. In such a situation CT scanning is
recommended.
Sonography
Also called Echography. It uses ultrasound to produces images of the
internal organs. Ultrasound is beyond human hearing power or above
20,000 Hz or 20 kHz. Visual record is called Sonogram or Echogram.
Ultra sound is produced through piezoelectric effect. Ultrasound is
produced by lead zirconate. Sex determination of Foetus using
Sonography is banned in 1994 under prenatal diagnostic act
Doppler ultrasound
Scanning
Used to scan blood flow in vessels, blood clots , and heart abnormalities.
HEI
Hall Effect Imaging. Used to pinpoint diseased tissues like cancerous
tissue.
Pace maker
Devised by Greatbach and Chardack in 1960. Pace maker has a pulse
generating device having a long lasting Lithium halide cell. Pace makers
may be External pace maker, Epicardial pace maker, Endocardial pace
maker, Permanent pace maker etc. Pace maker is an implant.
LASER
Used to detect gall bladder and kidney stones. Laser is a form of
monochromatic light. LASER is also used in surgery, to break
chromosomes in genetic engineering etc.
Intra aortic balloon pump Improve blood supply to heart muscles after a clot. It is used to save life
in emergency conditions by restoring the functions of organs. The
devices of intra aortic balloon pump are
1. Implants like artificial heart valve , arteries
2. Disposables like oxygenators, blood bags etc.
3. External prosthetics like artificial foot.
It assists heart in pumping of blood.
Angioplasty
Used to remove bocks in the coronary artery.
A balloon is used to remove the blocks. A contrasting
dye is injected to locate the block and then the
Balloon is inflated to clear the path of blood flow.
First coronary angioplasty was done in 1977.
Coronary angioplasty is also called as PTCA
(Percutaneous Transluminal Coronary Angioplasty)
It is also called Baloon Procedure.
Angiography or
Arteriography
A radio opaque contrast medium is used for the study of heart walls,
valves, atria, ventricles etc.
Artificial Arteries
Vascular grafts or arteries made of Dacron (fibrous plastic or Terylene)
or Teflon (polytetra fluro ethylene). Vascular graft is required in
Aneurysm.
Heart Lung bypass
Instrument used during open heart surgery. Roller pump takes the
function of heart and Oxygenator takes the function of lung
Blood bag
Used to store blood, separation of components of blood and transfusion
of blood.
Artificial blood
Perflurocarbon can function as blood.
Cyclopean
Also called Biological fluid connector. Blood purifying device.
Laennec
Invented Stethoscope
Phonocardiogram
Instrument used to amplify heart sounds.
Keratoplasy
Transplanting of cornea. It is safe because it will
not produce immune response due to the
lack of blood in the cornea.
Artificial valve
Heart valve made up of metal or rubber. Person carrying artificial valve
in the heart should have to take small doses of Anticoagulant daily to
preventing clot in the valve.
cDIVA
It is the Gene for human growth
Thermometer
Discovered by Galileo in 1593.
Defibrillator
Used to reduce fibrillation of heart by giving mild electric shock.
Haemometer
Used to measure the amount of haemoglobin per 100 ml blood.
Bertholt method
Quantitative measurement of Urea in blood plasma or serum. Blood urea
will decrease in early pregnancy.
Barium X ray
Used to investigate digestive tract.
Air encephalography
X ray test of the brain parts that contain fluid.
NMR
Nuclear Magnetic Resonance is the method used to map internal organs
including molecular structure. It completely avoids the use of ionizing
radiations. It uses radio frequency in a controlled magnetic field.
Resonance of Hydrogen in the water molecule and their energy release is
the basis of NMR.
Myoelectric arm
Used to move prosthetic hand and wrist.
Peritoneal dialysis
Used to remove fluid from peritoneum. In peritoneal dialysis, dialysate
pass in to abdominal cavity.
RBE
Relative Biological Effectiveness. It is related to radiation dose
Haemocytometer
Used to counting leucocytes.
Prosthesis
Implantation of artificial body parts Eg. Jaipur (Rajasthan) Foot. Sethi is
famous for Jaipur foot
Patch Clamp Technique
Patch Clamp Technique is a laboratory technique in electrophysiology that allows the study of single
or multiple ion channels in cells. This discovery made it possible to record the currents of single ion
channels for the first time, proving their involvement in fundamental cell processes such as action
potential conduction. Erwin Neher and Bert Sakmann developed the patch clamp in the late 1970s and
early 1980s.They received the Nobel Prize in Physiology and Medicine in 1991 for this work. Patch
Clamp technique can be applied to a wide variety of cells, but is especially useful in the study of
excitable cells such as neurons, cardiomyocytes, muscle fibers and pancreatic beta cells. It can also be
applied to the study of bacterial ion channels in specially prepared giant spheroplasts.
Positron emission tomography (PET)
Positron emission tomography (PET) is a nuclear medicine imaging technique which produces a
three-dimensional image or picture of functional processes in the body. The system detects pairs of
gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into
the body on a biologically active molecule. Images of tracer concentration in 3-dimensional space
within the body are then reconstructed by computer analysis. In modern scanners, this reconstruction is
often accomplished with the aid of a CT X-ray scan performed on the patient during the same session,
in the same machine.
Plasmon Resonance
The excitation of surface Plasmons by light is known as a Surface Plasmon Resonance or SPR. This is
observed in nanometer-sized metallic structures. Surface Plasmons, are surface electromagnetic waves
that propagate in a direction parallel to the metal or dielectric interface .This phenomenon is the basis
of many standard tools for measuring adsorption of material onto planar metal (typically gold and
silver) surfaces or onto the surface of metal nano particles.
Q Banding
Quinacrine mustard, an alkylating agent, was the first chemical to be used for chromosome banding.
T. Caspersson and his colleagues, who developed the technique, noticed that bright and dull
fluorescent bands appeared after chromosomes stained with quinacrine mustard were viewed under a
fluorescence microscope. Quinacrine dihydrochloride was subsequently substituted for quinacrine
mustard. The alternating bands of bright and dull fluorescence were called Q bands. Quinacrinebright bands were composed primarily of DNA that was rich in the bases adenine and thymine, and
Quinacrine-dull bands were composed of DNA that was rich in the bases guanine and cytosine.
SCANNING ELECTRON MICROSCOPE (SEM)
The scanning electron microscope (SEM) is a type of electron microscope that images the sample
surface by scanning it with a high-energy beam of electrons in a raster scan pattern. The electrons
interact with the atoms that make up the sample producing signals that contain information about the
sample's surface topography, composition and other properties such as electrical conductivity.
The types of signals made by an SEM can include secondary electrons, back scattered electrons,
characteristic x-rays and light (cathodoluminescence). These signals come from the beam of electrons
striking the surface of the specimen and interacting with the sample at or near its surface. In its primary
detection mode, secondary electron imaging, the SEM can produce very high-resolution images of a
sample surface, revealing details about 1 to 5 nm in size. Due to the way these images are created,
SEM micrographs have a very large depth of focus yielding a characteristic three-dimensional
appearance useful for understanding the surface structure of a sample. This great depth of field and the
wide range of magnifications (commonly from about 25 times to 250,000 times) are available in the
most common imaging mode for specimens in the SEM, secondary electron imaging, such as the
micrograph taken of pollen shown to the right. Characteristic x-rays are the second most common
imaging mode for an SEM. X-rays are emitted when the electron beam removes an inner shell electron
from the sample, causing a higher energy electron to fill the shell and give off energy. These
characteristic x-rays are used to identify the elemental composition of the sample. Back-scattered
electrons (BSE) that come from the sample may also be used to form an image. BSE images are often
used in analytical SEM along with the spectra made from the characteristic x-rays as clues to the
elemental composition of the sample.
Single-unit recording
Single Unit Recording is the use of an electrode to record the electrophysiological activity (action
potentials) from a single neuron. The electrode introduced into the brain of a living animal will detect
electrical activity that is generated by the neurons adjacent to the electrode tip. If the electrode is a
microelectrode, with a tip size of 3 to 10 micrometers, the electrode will often isolate the activity of a
single neuron. The activity consists of the voltages generated in the extra cellular matrix by the current
fields outside the cell when it generates an action potential. Recording in this way is generally called
"single-unit" recording. The recorded action potentials look very much like the action potentials that
are recorded intracellularly, but the signals are very much smaller (typically about 0.1 mV).
TRANSMISSION ELECTRON MICROSCOPE (TEM )
Transmission electron microscopy (TEM) is a microscopy technique whereby a beam of electrons is
transmitted through an ultra thin specimen, interacting with the specimen as it passes through it. An
image is formed from the electrons transmitted through the specimen, magnified and focused by an
objective lens and appears on an imaging screen, a fluorescent screen in most TEMs, plus a monitor, or
on a layer of photographic film, or to be detected by a sensor such as a CCD camera. The first practical
transmission electron microscope was built by Albert Prebus and James Hillier at the University of
Toronto in 1938 using concepts developed earlier by Max Knoll and Ernst Ruska.
Agrobacterium tumefaciens
It has the ability to transfer and stably integrate foreign DNA into plant genome. Nif genes are tied to
T1 plasmid and are allowed to integrate into genome of non-leguminous plants.
Azospirillum lipoferum
Nitrogen fixing bacteria present in the roots of Brazilian grasses and Maize. Scientists are trying to
associate Azospirillum with cereals to reduce the use of chemical pesticides.
Penicillin
Antibiotic obtained from Penicillium notatum and Penicillium chrysogenum. Penicillin is a broad
spectrum antibiotic. It prevents wall formation in bacteria and kills them.
Aspergillus niger
It is used in commercial preparation of citric acid from sugar beet and sugarcane molasses. It can
convert 40% of sucrose to citric acid.
Embryo rescue technique
Technique used to prevent the death of hybrid embryos. The technique involves excision and growth of
hybrid embryo in a culture on a nutrient medium. It helps to produce hybrids that are disease resistant.
Adaptive radiation
A phenomenon in evolution. It is the emergence of numerous species from a common ancestor
introduced into an environment presenting a diversity of new opportunities and problems.
Allosteric site
It is a specific site on the enzyme molecule. It is different from the active site. Molecule that binds to
the Allosteric site change the shape of the active site making the enzyme either more or less receptive
to the substrate.
Alpha diversity
It is defined as the diversity of organisms sharing the same community or habitat. A combination of
species richness and evenness is used to represent alpha diversity.
Alpha helix
It represents the coiling form of polypeptide. The spiral shape of the protein is due to alpha helix
coiling. Alpha helix is due to the formation of hydrogen bonds.
Amphidiploid
It is a tetraploid individual having 2 sets of chromosomes derived from two species. It is a form of
allotetraploid.
Apical dominance
It occurs during plant growth. Concentration of growth occurs at the tip of the shoot and the terminal
bud partially inhibits the growth of axillary bud.
Autoradiography
It is the method used to localize radioactive atoms in microscopic preparations of biological materials
by exposing a photographic film emulsion to radioactive atoms incorporated in the biological
specimen.
BAC
Bacterial Artificial Chromosome. It consists of F plasmid of bacteria and can be used for transferring
eukaryotic genes.
Balanced polymorphism
It is a type of polymorphism in which the frequencies of the coexisting forms do not change noticeably
over many generations.
Bacillus thuringienesis
It is the soil bacterium produces a crystal protein called Cry protein in its spores which is toxic to
larvae of certain insects. The gene encoding Cry protein is called cry gene and has been isolated and
efforts are being made by scientists to transfer this gene into Chick pea and other pulses to protect
them from severe damaged caused by insect pests.
Biopatency
Patency is a right given officially to an inventor to make or sell his/her invention and to prevent others
from copying it. Countries like USA, Japan and European union award Biopatency for strains of
microorganisms, cell lines, genetically modified plants and animals, DNA sequences, biotechnology
products, procedures etc.
Biopiracy
It is the unauthorized use of patent resources by organizations and multinational companies of other
nations. For example, the patent claimed by USA for the Basmati rice whose germplasm originally
belong to India. The protein Brazzein from West African plant Pentadipiandra brazeana which is a low
calorie sweetner has been patented in the USA.
Biowar
This involves the use of biological weapons against humans, crops and animals. Biological warfare
involves bioweapon agents or toxins which attack humans, crops and animals and its use in war has
been dated back to 5th century B.C. Bioweapon agents are contained in the containers and delivered as
powders, sprays etc. Some of the potent pathogens used in biowarfare are Anthrax, Small pox,
Botulinum pathogens.
Bioethics
It involves the set of standards that are used to regulate and monitor our activities in relation to
biological world. Biotechnology has greatly exploited the biological world and there are several
bioethical concerns which include over use, disrespect given to plants and animals and also the risk
involved in the experiments.
Biological magnification
It is a trophic process in which retained substances become more concentrated with each link in the
food chain.
Bioremediation
It is the use of microorganisms for the removal of pollutants.
Blood-Brain barrier
This is a specialized capillary arrangement in the brain that restricts the passage of most substances
into the brain, thereby preventing dramatic fluctuations in the brain’s environment.
Biological Oxygen Demand
It is the quantitative expression of the oxygen depleting impact. It is an expression of how much
oxygen is needed for microorganisms to oxidize their organic matter.
Bottle neck effect
Genetic drift resulting from reduction of a population, typically by natural disaster, such that the
surviving population is no longer genetically representative of the original population.
c-DNA
It is a duplex DNA complementary to m RNA synthesized from it by reverse transcription. It lacks
introns because there is no introns in m RNA. C DNA is called complementary DNA.
Cell mediated immunity
The type of immunity that functions in defense against fungi, protests, bacteria and viruses in side host
cells and against tissue transplants with highly specialized cells that circulates in the blood and
lymphoid tissues.
Chaparrel
A scrub land biome of dense, spiny, evergreen shrubs found along coasts where Cold Ocean currents
circulate off shore, characterized by mild, rainy winters and long, hot, dry summers.
Chemiosmosis
The ability of certain membranes to use chemical energy to pump hydrogen ions and then harness the
energy stored in the Hydrogen ion gradient to drive cellular work including ATP synthesis.
Co factor
Any non-protein molecule or ion that is required for the proper functioning of an enzyme. Co factors
can be permanently bound to the active site or may bind loosely with the substrate during catalysis
Competitive exclusion principle
The concept that when the populations of two species compete for the same limited resources, one
population will use the resources more efficiently and have a reproductive advantage that will
eventually lead to the elimination of the other population.
Complement system
A group of at least 20 blood proteins that cooperate with other defense mechanisms, may amplify the
inflammatory response, enhance phagocytosis or directly lyses pathogens; activated by the onset of the
immune response or by surface chemicals on microorganisms.
Convergent evolution
The independent development of similarities between species as a result of their having similar
ecological roles and selection process.
Corpus luteum
Secreting tissue in the ovary that formed from the collapsed follicle after ovulation and produces
progesterone.
Counter current exchange
The opposite flow of adjacent fluids that maximizes transfer rates. For example, blood in the gills
flows in the opposite direction in which water passes over the gills, maximizing oxygen uptake and
carbon dioxide loss.
Double Bohr Effect
Foetal hemoglobin takes oxygen from mother hemoglobin through the placenta due to double Bohr
Effect. Foetal hemoglobin dissociation curve shifts to left. Foetal hemoglobin is a tetramer having two
alpha chains and two gamma chains. So HbF is insensitive to a shift due to 2-3 DPG and the curve is
Sigmoid.
Oxygen dissociation curve
It is a graph that shows the percent saturation of hemoglobin at various partial pressures of oxygen.
Commonly a curve may be expressed with P50 value. This value represents the pressure at which the
erythrocytes are fifty percent saturated with oxygen. The purpose of the oxygen dissociation curve is to
show the equilibrium of oxyhemoglobin and non- bonded hemoglobin.
Surfactant
It is a lipid surface tension lowering agent present in the lining of alveoli. It is a mixture of Dipalmitoyl
Phosphotidyl Choline (DPPC), other lipids and proteins secreted by the type II alveolar epithelial cells.
Surfactant reduces the surface tension in the fluid on the surface of alveoli, allowing them to expand at
first breath and remain open there after.
2-3 DPG
2-3 Diphospho glycerate is a highly anionic organic phosphate created in the RBC, during glycolysis.
It binds to hemoglobin and reduces the oxygen affinity. This is essential to unload oxygen in the tissue
capillaries. In the absence of DPG, body makes more RBC. The RBC membrane become weak and
RBC become irregularly shaped and hemolyse.
Gene bank
Gene bank or Gene library is the collection of cloned genes, frequently comprising cells of the gene
from a particular species. Such libraries may consist of genomic sequences or DNA sequences, the
latter having being made from messenger RNA and intron sequences.
Transgenic organisms
Organisms that has become transformed following the introduction of new DNA into its genome is
called transgenic organism. Transgenic crop plants contain a gene or genes which have been artificially
inserted instead of plant acquiring them through pollination. The inserted gene sequence is called
Transgene may come from another unrelated plant or from a completely different species. For
example, Bt Corn with gene from Bacillus thuringienesis, resistant to over ripening of Tomato.
Transgenic animals have novel genes obtained from outside. For example, Plasminogen activator in
milk (Goat). Transgenic microbes are being used in industry for producing different bio chemicals and
various functions. For example, Pseudomonas putida has been changed by introducing Plasmids of
different strains for Alcoholic fermentation.
Bt Cotton, a transgenic crop variety, has been introduced in India. The Bt cotton variety contains a
foreign gene obtained from Bacillus thuringienesis. This bacterial gene, introduced genetically into the
cotton seeds protects the plant from Bollworm, a major pest of cotton. Bt cotton requires only 2 sprays
of pesticide while the normal variety requires 8 sprays. According to Indian Council of Agricultural
Research (ICAR), India uses about half of its pesticides on cotton to fight against Bollworm menacle.
Use of Bt cotton has led to a 3% - 27% increase in cotton yield in countries where it is grown
Gene transfer techniques
Used to transfer genes from one organism to another
1. Agrobacterium mediated gene transfer
2. Direct gene transfer using Biolistics gun, Electroporation, Microinjection etc.
Transgenic plants
The plants which carry additional stably integrated and expressed foreign genes transferred from other
genetic sources are called as transgenic plants.
Agrobacterium mediated transfer
The most common techniques used to transfer genes to Dicotyledonous plants using Agrobacterium.
Cereals are difficult to transform through Agrobacterium because they do not have the proper wound
response, a necessary requirement for transformation.
Transgenic vegetables
First transgenic plant Flavr Savr- delayed ripening tomato – introduced by Calgene Inc.
USA in 1994.
Cherry, Endless summer (tomato) – contains Bt protein gene against fruit borer.
Freedom II
Squash resistant to water melon mosaic virus
New leaf (Potato)
resistant to Colorado beetle (Leptinotarsa decemlineata)
AmAl
Amaranth
Parthenocarpy fruits Seed less fruits
Golden rice
with high Vit. A content
Biological magnification
It is the process whereby certain substances such as pesticides or heavy metals move up the food chain,
toxins build up a successive link of the food chain. It works their way into river or lakes and is eaten by
aquatic organisms such as fish which in turn are eaten by large birds, animals or humans. The
substance becomes concentrated in the chain. It is like a magnifying glass that makes things look
bigger. Biological magnification makes toxin get bigger and stronger in the ecosystem.
Eg. 1 Some pesticides are considered as Environmental Estrogens. These chemicals interfere with
sex hormones and cause decreases sperm counting, breast cancer, testicular cancer, mis carriage etc.
Methoxyclor, Atrazine, Benomyl are examples.
Eg. 2 Beetals may have very low level of fat soluble pesticides, but the pesticides will build much
greater levels till in a human that eats the beetal eating bird.
Eg. 3 DDT in food chain of coastal water of long island.
Genetic map or Linkage map
These are maps based on the recombination frequency. It includes determination of linkage groups and
determination of map distance. A linkage group does not show the physical distance between genes but
rather their relative positions as determined by how gene loci are inherited together. The closer two
genes are, the more often they will be inherited together. Linkage distance is measured in
Centimorgan unit ( cM)
Chromosome map
These are used to identify the location of genes using special cytological techniques such as
Chromosome Banding.
Bio-informatics
This is a new computer aided technology to store, retrieve, analyze or predict the composition or
structure of bio-molecules. Classical bio-informatics mainly deals with the sequence analysis of DNA
or Protein. The Human Genome Project is currently being completed with the help of Bio-informatics.
New Bio-informatics includes Medical imaging or Image analysis, biologically inspired computation
like Genetic Algorithms.
Pesticides
Organochlorides
DDT, BHC, Aldrin, Endosulphan – These are lipophilic compounds accumulate
In fat depots like liver.
Organophosphates
Malathion, Parathion, Feritrothion- These affect nervous system.
Carbamates
Carbaryl, Carbofuran
- Inhibit Acetylcholine esterase.
Highly toxic pesticides
Well known pesticide
DDT, BHC, Carbofuran, Aldrin
Parathion
Insecticide for Malaria control
Malathion
Furudan
It is Carbofuran
Baygon
It is Propoxus
Herbicides
destroy the weeds by affecting the Photosystem II.
Pesticide Thread Mill
More expensive and more poisonous pesticides used to obtain
target. Eg. Pesticides for Cotton in India.
Biopesticides
These are biological agents used to control pests. Devine and Colego first used Fungal spores in weed
control.
Confusion technique of pest control uses Pheromones. It is used in IPM. Ecdysone,
JH etc are insect hormones used to control pests in IPM.
Pyrethrum is obtained from Chrysanthemum cinerariifolium is a natural plant insecticide. It is usedto
make Mosquito coils.
Neem contains an Anti-feedant called Azadiraclitin.
Food crops
Barley, Cotton, Sorghum
Ethiopia
Maize
Mexico, Central America
Sunflower
USA
Pineapple, Rubber
Brazil
Tomato, Potato
Aeruvian Andes
Orthodox seeds
These are seeds withstand low moisture and low temperature. Eg. Cereals, Legumes.
Recalcitrant seeds
These are seeds killed by drying and freezing. Eg. Jack fruit, Tea, Cocoa, Rubber, Palm.
ANIMAL KINGDOM-ONE WORD ANSWERS
1. Choanocytes or Collar cells of Sponges are concerned with intracellular digestion.
2. Physalia (Portuguese man of War) is a polymorphic form with zooids like Gastro zooid
(feeding), Gonozooid (reproduction), Dactylozooid (protection) and Pneumatophore (floating).
3. Alconium or “Dead man’s Finger” belongs to the class Anthozoa. Coral is formed of Calcium
carbonate.
4. The single polyp in the coral colony is called as Corallite and the colony as Corallum. Some
of the common marine coelenterates are Pennatula (Sea Fan), Virgularia (Sea Whip), Gorgonia
(Sea Fan) etc. Lakhsdeep, Rameswaram and Fiji are Coral islands.
5. Hirudo medicinalis is a leech used in Ayurvedic treatment to remove blood clots. There are 33
segments in the body of leech. Body cavity is filled with Botryoidal tissue. Hirunaria granulose
is the ‘Cattle leech” and Haemodipsa is the “Land leech’
6. Ampullae of Lorenzini are the sense organs of fishes. Placoid scales of Shark resemble the
tooth of mammals in structure.
7. Protopterus is the typical lung fish. Periophthalmus and Polypterus are lung fishes without
internal nostrils. Anguilla is the larval form of Leptocehalus.
8. Rhacophorus is called as” Obstetric toad”.
9. Toxin secreted by the Parotid glands of Toad contains Bufotalin and Bufogin. Bidder’s organ of
toad is endocrine in function.
10. Labyrinthodontia of Devonian period evolved into Amphibians. Crossopterygian fish Latimaria
is considered as the ancestor of Amphibians.
11. Cotylosaurus is the “Stem Reptile” disappeared during Triassic period. High temperature, lack
of vegetation, increased aridity, and absence of mechanisms to protect eggs from mammals are
the reasons for the extinction of Dinosaurs.
12. Heloderma is the only poisonous lizard. Sphenodon is a living fossil.
13. Mammals evolved from reptile like Dimetrodon in Triassic period.
14. Mammals typically have 7 cervical vertebrae. But Sloth, Sea cow and Mantee have 6 to 9
cervical vertebrae.
15. Prototheia is the only one group laying eggs (Echidna, Platypus). Corpus Callosum is absent in
Marsupials (Kangaroo, Opossum).
16. Bats belong to the order Chiroptera. Vampire bat is a blood sucking bat.
17. Tree shrew is considered as the remote ancestor of mammals.
18. Hognose Bat is the smallest mammal (formerly Pigmy water shrew was considered as the
smallest mammal). Dolphin is the intelligent aquatic mammal.
19. Echolocation is found in Bats, Whale and Dolphins. Giraffe is the tallest mammal and Cheetah
is the fastest mammal. Three toed Sloth is the slowest terrestrial mammal.
20. Enhydra lutris is the slowest aquatic mammal.
21. Gorilla is the largest Ape and Chimpanzee is the most intelligent Ape.
22. Gibbon is the only Ape found in India.
23. Closest primate relative of man is Gorilla.
24. Blue whale is the largest living mammal (30-50 tons body weight).
EVOLUTION – ONE WORD ANSWERS
25. Theory of Biogenesis was put forwarded by Louist Pasteur in 1862 to explain the origin of life.
It states that life originate only from pre existing life.
26. Protobionts are aggregates of artificially produced pre-biotic molecules in experimental
conditions. It shows the capacity to maintain internal environment but lacks the ability of
division.
27. Coacervate is a mixture of proteins and polysaccharides surrounded by a film of water. Since a
lipid bilayer is absent, it lacks the ability to divide.
28. Congogeny refers to the evolution of perception, expression and communication in the
primitive organism (Eiobionts). Congogeny marked the diversification and evolution of
photosynthesis.
29. Specimens with fake structures similar to plant parts are called as Pseudofossils.
30. Paleontology is the study of fossils.
31. Fossils are dead remains of plants and animals lived in the past ages. Fossils may be Unaltered
fossils (whole body buried in resin or ice),
32. Petrified fossils (replacement of body parts by minerals),
33. Moulds (hardened mud surrounding the fossil) Casts (petrified fossil with moulds) and Prints
(foot prints of animals).
34. Determination of the age of fossils is called Dating of fossils. Various methods used for dating
the fossils are Radioactive clock method, Radiocarbon method and Potassium Argon method.
35. The most accurate method of fossil dating is Electron-Spin Resonance method.
36. Convergent evolution is the formation of similar structures in unrelated groups of organisms.
Wings of insects and birds evolved in the same line. Aquatic vertebrates also show characters
evolved through convergent evolution.
37. Parallel evolution is the convergent evolution in closely related animals. For example the
running adaptations in Horse and Deer.
38. Homologous organs have same structure but perform different functions. Examples are
Pentadacyl limbs of vertebrates, Mouth parts of insects etc.
39. Molecular Homology is also found in animals. Example is the Blood Proteins of Man and
Apes.
40. Analogous organs have different structures but perform same functions. Examples are Wing of
insects, birds and bat, Flippers of whale and fins of fishes etc.
41. Vestigial organs are rudimentary non functional organs which were well developed and
functional in the ancestors. About 90 Vestigial organs are found in man. Some of them are
Nictitating membrane, Coccyx, Ear muscles, Vermiform appendix, Wisdom teeth, Hair on the
body etc. Rudimentary pelvic girdle of Python, Wings of flightless birds, and Splint bone in the
leg of horse are also vestigial organs.
42. Connecting link is an organism which possesses the characters of two different groups.
Examples are Euglena, (plant and animal) Proterospongia (protozoa and porifera), Peripatus
(annelida and arthropoda), Neoplina (annelida and mollusca), Lung fishes, Egg laying
mammals, Archaeopteryx etc.
43. Atavism or Reversion is the reappearance of ancestral characters in present animals. Examples
are ability to move ear pinna, hairy body, short tail, long canines etc.
VITAMINS-ONE WORD ANSWERS
Vitamins are regulators necessary for the normal metabolic activities. Deficiency of vitamins
(Hypovitaminosis) causes Deficiency diseases. Vitamins are classified into Fat soluble (Vit. A, D, E
and K) vitamins and Water soluble (Vit. B complex and Vit. C) Vitamins.
Fat-soluble vitamins
Vitamin A is called as Retinol, which is necessary for the synthesis of visual pigment Rhodopsin in the
retina. It is richly present in red colored fruits and vegetables, milk etc. Deficiency of Vitamin A
causes Nyctalopia (Night blindness) and Xerophthalmia (hardening of cornea).
Vitamin D is the Ergostertol synthesized in the skin from 7-dehydro cholesterol by the action of UV
rays of sunlight. Vitamin D is present in butter, liver, eggs etc and is essential for the absorption of
calcium and phosphorous from the intestine. Deficiency of vitamin D causes Rickets (malformed
skeleton) in children and Osteomalacia (weakening of bones) in adults.
Vitamin E or Tocopherol is necessary for the reproductive functions. It is present in green vegetables,
egg yolk etc.
Vitamin K or Phylloquinone is the Coagulation vitamin necessary for the synthesis of Prothrombin in
the blood. It is present in leafy vegetables, egg, yolk etc. The colon bacteria also synthesize it.
Water soluble vitamins
Vitamin B complex and Vitamin C are water-soluble and cannot be stored in the body. Therefore daily
supply of these vitamins is required.
Vitamin B1 or Thiamine is present in rice bran, yeast etc. It forms a major component of coenzyme
carboxylase. Deficiency of Thiamine leads to Beriberi (loss of appetite, weakness etc.)
Vitamin B2 is Riboflavin is necessary for the formation of FAD. It is present in green vegetables and
its deficiency is Cheilosis (ulcers in the lips and tongue)
Vitamin B3 or Niacin is the active part of NAD and is available in yeast, milk, pulses etc. Pellagra
(inflammation of skin, diarrhoea) is the deficiency disease.
Vitamin B5 (Panthothenic acid), Vitamin B6 (Pyridoxine) Vitamin H (Biotin) are also necessary for
the cellular activities. Vitamin B12 or Cyanocobalamin is a Cobalt containing vitamin present in milk,
fish etc. It is also synthesized in the intestine by the bacteria. Cobalamine is necessary for the synthesis
of haemoglobin so the deficiency leads to Pernicious anemia.
Vitamin C or Ascorbic acid is richly available in Citrus fruits like lemon, orange etc. The richest
source of Vit. C is Gooseberry. Vit.C is necessary for the immune system, skin, connective tissue etc.
Deficiency of Vit. C leads to Scurvy.
Genetics Capsule
44. Codominance is the condition in which two dominant genes express together. Eg. AB blood
group in man, Coat color in Cattle etc. Incomplete dominance is the partial expression of two
dominant genes to produce a mixture of two characters. Eg. Sickle cell anemia, Pink flower in
Mirabilis.
45. Polygenes (Multiple genes) are groups of genes controlling the same character. Eg. Skin color
in man.
46. Multiple alleles are alternate forms of a gene expressing the same character. Eg. Blood groups
in man, Coat color in Rabbit etc.
47. Epistatic gene suppresses the character of a gene (Hypostatic Gene). Eg. Coat color in Dogs,
Coat color in Mice.
48. Pleotropism is the condition in which a gene produces multiple effects. Eg. Gene for sickle
cell anemia, Eye color in Drosophila.
49. Lethal genes are harmful genes destroying the possessor. Eg. Thalassemia and Huntington’s
chorea in man, leaf color in Snapdragon (Homozygous dominant). Some times homozygous
recessive genes become lethal. Eg. Congenital Ichthyosis and Amaurotic idiocy in man.
50. Pedigree analysis is the method to trace back the ancestral characters by taking one or more
characters from an individual. In the Pedigree tree, Squares represents males and Circles
females. Shaded squares or circles indicate dominant traits and open squares or circles denote
recessive traits.
51. Giant chromosomes are found in Dipteran insects. Polytene chromosome (Salivary gland of
Drosophila) and Lamp brush chromosome (Amphibian Oocytes) are giant chromosomes. SAT
chromosome possesses a swollen part (Satellite body) at the tip of the chromosome.
52. Somatic genes in the Y chromosomes are called Y linked or Holandric genes. Eg. Gene
producing Hypertrychosis (hair in the ear pinna) in man.
53. Sex limited characters express only in one sex. It will not express in the other sex even if the
gene is present. Eg. Feather pattern in Poultry, premature baldness in human males, milk
production in cattles.
54. Sex influenced characters behave like Dominant in one sex and Recessive in the other sex.
Phenotype will be different even though the genotype is same. Eg. Horn in Sheep, baldness in
man, Hare lip etc.
55. Mutation is a sudden heritable change in organisms leading to variations. Mutation was
observed by Hugo de Vris in Oenothera lamarkiana (Evening Prim rose).
56. Gene mutations (Point mutations) affect the genes.
57. Cladogenic agents (X-ray, Gamma rays) are chromosome breaking agents.
58. Cri-du-chat syndrome is caused due to a deletion in the short arm of 5th chromosome.
59. Philadelphia chromosome is the small 22nd chromosome in man produced due to the
translocation between the chromosomes 9 and 22. It is seen in patients with Chronic myeloid
leukemia (CML).
60. Colchicine is called as Mitotic Poison since it destroys spindle fibers and arrest mitosis. It is
used to induce Polyploidy in plants. Triticale is the first man made Cereal produced by
crossing Wheat and Rye and then inducing polyploidy.
61. Mutagens are agents causing mutations. Physical mutagens are X-ray, alpha, beta, gamma
rays, UV rays etc. Chemical mutagens include Nitrous acid, Ethyl methane sulphonate (EMS),
Acridine orange etc. Sharbati Sonora is a variety of Wheat produced by induced mutation.
62. Cistron is the smallest unit of DNA that transcribes a messenger RNA.
63. Recon is the unit of recombination and Muton is the part of DNA that undergoes mutation.
64. B-DNA is the usual form of right handed DNA with 10 base pairs in one turn. A-DNA
(11 base pairs), C-DNA (9 base pairs) and D-DNA (8 base pairs) are forms of DNA produced
in experimental conditions.
65. Z-DNA is the left handed DNA discovered by Rich, Nordheim and Wang in 1984. It has 12
base pairs per turn.
66. Palindrome DNA has inverted repetition of base sequences.
67. H-DNA contains inverted repetition of base sequences to form Triple helix DNA.
68. Watson, Crick, Wilkins and Rosalind Franklin are associated with the Double Helical model of
DNA. There are 10 base pairs per turn in the DNA. The base pairs are separated by a distance
of 3.4 Angstrom so the total length of the turn is 34 Angstroms.
69. Hydrogen bonds in the DNA stabilize the topology and antiparallel nature of DNA.
70. Phospho diester bonds maintain the polarity (3’-5’ and 5’-3’) of the DNA strands.
71. Helicase is the enzyme that separate DNA strands during replication.
72. Topisomerase (Relaxing enzyme) reduces tension in the DNA during unwinding. DNA
Polymerases I , II and III are DNA synthesizing enzymes. DNA polymerase III is the most
active enzyme. Bacterial DNA Polymerases are Pol I and Pol II (DNA repair) and Pol III
(Chromosome replication).
73. Ligase (Molecular glue) joins DNA segments after synthesis.
74. Telomerase is the enzyme containing RNA and protein. It terminates DNA replication.
75. Reverse Transcriptase is the bacterial Polymerase that synthesise DNA from RNA.
76. Primase (RNA polymerase) is used to synthesize Primer RNA during replication.
77. RNA Editing is the modification of the m-RNA before translation.
78. Recombinant DNA technology involves manipulation of DNA which involves DNA cloning,
DNA profiling etc.
79. R-DNA or Recombinant DNA contains a bacterial plasmid and a desired gene sequence of
another organism.
80. Restriction enzymes are “Molecular Scissors” that cut double stranded DNA at specific sites
producing ‘Staggered ends’. These enzymes are present in bacteria to destroy foreign DNA
such as Viral DNA. The enzyme will not destroy the own DNA of bacteria because it is kept in
the methylated form. Most widely used restriction enzymes are Eco R1, Bam 1, Hind III etc.
Molecular genetics
81. Cistron is the smallest unit of DNA that transcribes a messenger RNA. Recon is the unit of
recombination and Muton is the part of DNA that undergoes mutation.
82. B-DNA is the usual form of right handed DNA with 10 base pairs in one turn. A-DNA
(11 base pairs), C-DNA (9 base pairs) and D-DNA (8 base pairs) are forms of DNA produced
in experimental conditions. Z-DNA is the left handed DNA discovered by Rich, Nordheim and
Wang in 1984. It has 12 base pairs per turn. Palindrome DNA has inverted repetition of base
sequences. H-DNA contains inverted repetition of base sequences to form Triple helix DNA.
83. Watson, Crick, Wilkins and Rosalind Franklin are associated with the Double Helical model of
DNA. There are 10 base pairs per turn in the DNA. The base pairs are separated by a distance
of 3.4 Angstrom so the total length of the turn is 34 Angstroms. Hydrogen bonds in the DNA
stabilize the topology and antiparallel nature of DNA. Phospho diester bonds maintain the
polarity (3’-5’ and 5’-3’) of the DNA strands.
84. In Semi-conservative replication of DNA (proposed by Matthew, Mehelson and Stahl), two
daughter DNA are formed each having a new and old strands. In Conservative replication, the
parent helix remains intact. In Dispersive replication, all the four strands of two daughter DNA
are mixture of parental and daughter DNA. Rolling circle model of DNA replication is
proposed for the replication of Circular DNA of bacteria.
85. Helicase is the enzyme that separate DNA strands during replication. Topisomerase (Relaxing
enzyme) reduces tension in the DNA during unwinding. DNA Polymerases I , II and III are
DNA synthesizing enzymes. DNA polymerase III is the most active enzyme. Bacterial DNA
Polymerases are Pol I and Pol II (DNA repair) and Pol III (Chromosome replication). Ligase
(Molecular glue) joins DNA segments after synthesis. Telomerase is the enzyme containing
RNA and protein. It terminates DNA replication. Reverse Transcriptase is the bacterial
Polymerase that synthesise DNA from RNA. Primase (RNA polymerase) is used to synthesize
Primer RNA during replication.
86. DNA replication occurs in the 5’-3’ direction because the DNA polymerase III can act only in
this direction. “Leading strand” synthesis occurs in the 5’-3’direction. “Lagging strand”
synthesis (Discontinuous synthesis) occurs as DNA segments called “Okasaki Fragments”.
This is because the second strand of DNA has 3’-5 direction and Polymerase III can act only in
the 5’-3’ direction.
87. Beadle and Tatum conducted experiments in Neurospora crassa (Pink bread mold) to show the
relation ship between genes and enzymes. Wild type Neurospora (Prototroph) grow in Minimal
medium containing few salts and minerals. Mutant forms (Auxotroph) grow only when amino
acids like Ornithine, Citrulline and Arginine are added to the culture. Beadle and Tatum
conducted tetrad analysis in Neurospora and proposed the “One Gene One Enzyme”
hypothesis.
88. RNA Splicing involves the removal of Introns (non coding sequences) from the m-RNA. Then
the Exons ( coding sequences) are joined together. RNA Editing is the modification of the mRNA before translation. SnRNPs or Spurps are ribonucleoproteins binds to the m-RNA during
RNA splicing. Spliceosomes are formed by the interaction of SnRNPs with other proteins.
RNA capping is the process by which a guanine nucleotide (with methyl group) is added to the
5’ end of RNA after splicing. RNA cap determines the site of translation. PolyA tailing is the
process by which a long tail of Adenine residue is added to the 3’ end of m-RNA during
splicing. Ribozymes are RNA molecules act as enzymes. RNase P is a Ribozyme.
89. Recombinant DNA technology involves manipulation of DNA which involves DNA cloning,
DNA profiling etc. R-DNA or Recombinant DNA contains a bacterial plasmid and a desired
gene sequence of another organism. Restriction enzymes are “Molecular Scissors” that cut
double stranded DNA at specific sites producing ‘Staggered ends’. These enzymes are present
in bacteria to destroy foreign DNA such as Viral DNA. The enzyme will not destroy the own
DNA of bacteria because it is kept in the methylated form. Most widely used restriction
enzymes are Eco R1, Bam 1, Hind III etc.
Classical Genetics
90. Germinal variations affect the reproductive cells. These are also called as Fluctuating
variations, Sports or Saltations. Germinal variations are heritable. Genome denotes to the
haploid set of chromosomes in a cell. Test cross is the back cross of F1 generation with the
Recessive parent. Alleles are the alternate forms of a gene. Locus is the position of a gene.
91. Correns and Tschermak rediscovered Mendelism. Bateson and Punnet discovered
Complementary action of genes. Davenport discovered Polygenic inheritance (Skin color) in
man. Waldeyer coined the term Chromosome. Balbiani discovered Polytene chromosomes in
Drosophila. Muller discovered mutagenic property of X- rays. Hershey and Chase conducted
experiments in viral replication. Jacob and Monad proposed the Operon concept. Alec Jeffrey
introduced DNA finger printing. Kari Mullis discovered Polymerase chain reaction (PCR).
92. Codominance is the condition in which two dominant genes express together. Eg. AB blood
group in man, Coat color in Cattle etc. Incomplete dominance is the partial expression of two
dominant genes to produce a mixture of two characters. Eg. Sickle cell anemia, Pink flower in
Mirabilis. Polygenes (Multiple genes) are groups of genes controlling the same character. Eg.
Skin color in man. Multiple alleles are alternate forms of a gene expressing the same character.
Eg. Blood groups in man, Coat color in Rabbit etc. Epistatic gene suppresses the character of a
gene (Hypostatic Gene). Eg. Coat color in Dogs, Coat color in Mice. Pleotropism is the
condition in which a gene produces multiple effects. Eg. Gene for sickle cell anemia, Eye color
in Drosophila. Lethal genes are harmful genes destroying the possessor. Eg. Thalassemia and
Huntington’s chorea in man, leaf color in Snapdragon (Homozygous dominant). Some times
homozygous recessive genes become lethal. Eg. Congenital Ichthyosis and Amaurotic idiocy in
man.
93. Pedigree analysis is the method to trace back the ancestral characters by taking one or more
characters from an individual. In the Pedigree tree, Squares represents males and Circles
females. Shaded squares or circles indicate dominant traits and open squares or circles denote
recessive traits.
94. Hofmeister first reported Chromosomes in 1849. Sutton and Bovery in 1902 independently
proposed the Chromosome theory of Heredity. Chromosomes may be Metacentric (centromere
in the middle), Submetacentric (centromere towards one end), Acrocentric (centromere near the
end) and Telocentric (centromere at the tip). Giant chromosomes are found in Dipteran insects.
Polytene chromosome (Salivary gland of Drosophila) and Lamp brush chromosome
(Amphibian Oocytes) are giant chromosomes. SAT chromosome possesses a swollen part
(Satellite body) at the tip of the chromosome.
95. Somatic genes in the Y chromosomes are called Y linked or Holandric genes. Eg. Gene
producing Hypertrychosis (hair in the ear pinna) in man. Sex limited characters express only in
one sex. It will not express in the other sex even if the gene is present. Eg. Feather pattern in
Poultry, premature baldness in human males, milk production in cattles. Sex influenced
characters behave like Dominant in one sex and Recessive in the other sex. Phenotype will be
different even though the genotype is same. Eg. Horn in Sheep, baldness in man, Hare lip etc.
96. Mutation is a sudden heritable change in organisms leading to variations. Mutation was
observed by Hugo de Vris in Oenothera lamarkiana (Evening Prim rose). Gene mutations
(Point mutations) affect the genes. It may be Deletion (removal of bases), Addition or Insertion
and Substitution (replacement of one base by another one). Substitution may be Transition
(Purine-Purine or Pyrimidine-Pyrimidine change) or Tranversion (Purine-Pyrimidine change
or vice versa). Transition is caused by Tautomerization (shifting of protons), Deamination
(removal of amino group) or through base analogues (5-Bromo Uracil).
97. Gene mutations change the arrangement of genetic code in the DNA. So these are called Frame
shift mutations. Mis-sense mutation changes the amino acid sequence in the protein. Non
sense mutations results in termination codons. Silent mutations do not alter the amino acid
sequence in the protein. Cladogenic agents (X-ray, Gamma rays) are chromosome breaking
agents. Cri-du-chat syndrome is caused due to a deletion in the short arm of 5th chromosome.
Philadelphia chromosome is the small 22nd chromosome in man produced due to the
translocation between the chromosomes 9 and 22. It is seen in patients with Chronic myeloid
leukemia (CML).
98. Colchicine is called as Mitotic Poison since it destroys spindle fibers and arrest mitosis. It is
used to induce Polyploidy in plants. Triticale is the first man made Cereal produced by crossing
Wheat and Rye and then inducing polyploidy.
Mutagens are agents causing mutations. Physical mutagens are X-ray, alpha, beta, gamma rays,
UV rays etc. Chemical mutagens include Nitrous acid, Ethyl methane sulphonate (EMS),
Acridine orange etc. Sharbati Sonora is a variety of Wheat produced by induced mutation