INHERITANCE
Q. Define the following terms.
GENETICS
Genetics
is the branch of biology that is concerned with the study of genes, genetic
variation and heredity in organisms.
VARIATIONS
Genetic
variation is the difference in DNA among individuals or the differences between
populations.
There
are multiple sources of genetic variation, including mutation and genetic
recombination.
HEREDITY
The
way by which genes transmit characters from parents to offspring is called
Heredity.
INHERITANCE
The
process by which genetic information is passed from one parent to offspring is
called inheritance.
GENE
A
unit of heredity which is transferred from parent to offspring and is held to
determine some characteristics of the offspring is called gene.
GENE LOCUS
The part of the chromosome where gene resides is
called gene locus.
ALLELE
The variation in the gene of a trait gives rise to
two or more than two alternative forms which is called allele or allelomorph.
Q. Define chromosomes. Also describe the types of chromosomes.
CHROMOSOMES
The
term Chromosomes is given by German embryologist Walter Fleming in 1882.
Chromosome can be define as a threadlike structure of nucleic acids and proteins found in the nucleus of most living cells, carrying genetic information in the form of genes.
TYPES OF CHROMOSOMES
Chromosomes
are made up of DNA and basic protein, Histones, appear during the cell division
in the shape of rod. It has two parts arms and centromere. Depending upon
position of centromere, their types are:
·
Metacentric
·
Sub metacentric
·
Acrocentric OR Sub -telocentric
·
Telocentric
|
Metacentric |
Chromosomes
with equal arms |
|
Sub metacentric |
Chromosomes
with un equal arms |
|
Acrocentric OR Sub –telocentric |
Rod
like chromosomes with one arm very small and other very long. The centromere
is sub terminal. |
|
Telocentric |
Location
of centromere at the end of chromosomes |
Q. Describe the chemical composition of
Chromosome.
CHEMICAL COMPOSITION OF
CHROMOSOME
The
chemical material of chromosome is a nucleoprotein (Deoxyribo Nucleoprotein)
called chromatin. Chromatin consists of 40% DNA and 60% protein part.
DNA
is made up of billions of units called Deoxyribo-nculeotide. Each nucleotide is
made up of:
·
Deoxy
ribose sugar
·
Phosphoric
acid
·
Nitrogenous
bases
Q. Describe brief structure of DNA.
STRUCTURE OF DNA
The
double helix structure of DNA was suggested by Watson and Crick. According to
this model,
·
DNA
is a double helical structure,
·
Each
helix is a polynucleotide, which twist around each other,
·
The
outer part of helix is called upright which are made up of Deoxy-ribose sugar
and phosphate.
·
The
inner part of helix is called Rungs which are made up of paired nitrogenous
bases,
·
Both
helix are complementary to each other and held together by Hydrogen bond,
·
Complementary
helixes have complementary base pairs i.e.
o
Adenine
pairs with thymine
o
Cytosine
pairs with guanine
Q. Define replication.
REPLICATION
The
process of duplication of DNA in the nucleus is called Replication.
Q. What is mean by central dogma of protein
synthesis by gene?
CENTRAL DOGMA
The
central dogma refers to a set of beliefs where a gene expresses by synthesizing
a protein. This protein produces a metabolical product which further develops
into a character.
Q. How does the transfer of genetic information
take place?
The
genetic information transfers from DNA to mRNA than to ribosome in cytoplasm.
The process consists of two steps of protein synthesis.
·
Transcription
·
Translation
Q. Write brief note on Transcription and
Translation.
TRANSCRPTION
The
process of copying a segment of DNA to RNA is called Transcription.
The
step of protein synthesis where information from DNA is copied in complimentary
form in RNA is called transcription.
The
mRNA transfers this information from nucleus to cytoplasm.
TRANSLATION
In
the second step, two other types tRNA and rRNA translate the information of
mRNA into the specific sequence of amino acid which help to synthesize the
protein.
Q. Who is Gregor John Mendel? How many
characters did he study?
Gregor
John Mendel is known as Father of Genetics. He studies seven traits
(characters) in pea plants one by one including;
·
Height
·
Seed
shape
·
Pod
shape
·
Seed
color
·
Flower
color
·
Flower
position
·
Pod
color
Q. What is mean by pure breed?
Pure
breed refers to the offspring having exactly similar characters as of the
parent plant. The pure breed results in the process of self fertilization.
Q. Define the following terms.
DOMINANT
The
factor/character that expresses and masks the expression of other factor in
heterozygous condition is called dominant character.
RECESSIVE
The
factor/character that is unable to expresses and masks the expression of other
factor in heterozygous condition is called recessive character.
PHENOTYPE
It
is the physical appearance of the trait on the basis of inherited genes like
tall, dwarf, round, wrinkle etc.
GENOTYPE
The
genetic makeup of a trait is called Genotype. For instance; TT, Tt, tt etc.
HOMOZYGOUS
An
individual having same factors (allele) of a trait called homozygous.
For
instance; TT (factor for tallness)
HETEROZYGOUS
An
individual having different factors (allele) of a trait called heterozygous.
For
instance; Tt (factor for tallness and dwarfness, both)
PARENTAL GENERATION (P1)
The
original true breeding organisms are called parental generation or P1
generation.
FIRST FILIAL GENERATION (F1)
The
offspring of true breeding organisms are called first filial generation or F1
generation
SECOND FILIAL GENERATION (F2)
The
offspring of first filial generation produced by crossing self fertilization
are called second filial generation or F2 generation.
Q. Discuss law of complete Dominance.
LAW OF COMPLETE
DOMINANCE
According
to Gregor John Mendel,
‘When a pair of
contrasting characters (heterozygous) is brought together in a cross, only
one factor will express in the offspring while the other character will
be masked.’
OR
‘Complete dominance
refers to a relationship between two versions of a gene in which presence of a
dominant allele will always mask the presence of recessive allele.’
EXPERIMENT
Mendel
crossed pure tall stem and short stem. He found all the plants were of tall
stem in first generation. He repeated his experiment on pea plants with various
traits having contrasting characters, and got the same result.
P1
Generation Tall Short (Dwarf)
Genotype
TT tt
Gametes
T t
F1
generation Tt
Q. State and explain Law of independent
assortment OR law of purity of gametes.
LAW OF SEGREGATION OR
LAW OF PURITY OF GAMETES
This
law states that; ‘An assortment of each pair of traits is independent to
other.’
OR
‘In
an organism, the factor exists in pairs but during gamete formation these
factors segregate cleanly from each other.’
EXPERIMENT
Mendel
crossed pure tall and dwarf plant and got all heterozygous tall plants in F1
generation. He allowed to F1 generation to self pollinate. But in the F2
generation, he found both tall and dwarf stem plants in the ration of 3:1.
CONCLUSION
Mendel
concluded that when the plants of F1 generation form their gametes, the factors
separate or segregate again in such a way that only one of the two alleles
enters each gamete.
|
|
T |
T |
|
T |
Tt |
Tt |
|
T |
Tt |
tt |
Q. State and explain Mendel’s law of independent assortment.
LAW OF INDEPENDENT
ASSORTMENT
It
states that,
‘The genes of assorted
traits are independent in their inheritance.’
OR
‘Member of one pair of
genes separate from each other during gametes formation.’
EXPERIMENT
Mendel
crossed yellow cotyledon and rounded seed containing plant with green cotyledon
and wrinkled seed containing plant. He observed all the plants with yellow
cotyledon and round seeds.
Parental
generation RY ry
F1
generation RyYy
Mendel
self fertilized the F1 generation and observed the following results.
|
|
RY |
rY |
Ry |
Ry |
|
RY |
RRYY |
RyYY |
RRYy |
RrYy |
|
rY |
RyYY |
rrYY
|
RryY |
rrYy |
|
Ry |
RRYy |
RrYy |
RRyy |
Rryy |
|
ry
|
RrYy |
rrYy |
Rryy |
Rryy |
Mendel calculated the F2 generation in the ratio of 9:3:3:1 for the four phenotypes which shows the genes for seed color and seed structures are independent in their inheritance.
CONCLUSION
Mendel’s
experiment proved that allele for round seed is dominant over wrinkled while
yellow cotyledon over green.
Q. What is mean by multiple allele?
MULTIPLE ALLE
Some
trait has more than two and more than two alternative forms which are called
multiple alleles.
The
first ever discovered Multiple allele in Human is ABO Blood group.
Q. Draw a table to show the antigens of ABO
Blood group.
|
Blood group |
Antigen |
Genotype |
Phenotype |
|
A |
A |
IA‑IA IA‑i |
A
homozygous A
heterozygous |
|
B |
B |
IB‑IB IB‑i |
B
Homozygous B-heterozygous
|
|
AB |
A and B |
IA‑IB |
AB
Heterozygous |
|
O |
None |
i.i |
O
Homozygous |
What is mean by Rh Blood type?
Rh Blood
Rh
gene produces a protein which is found on the surface of RBC as well. This
trait has 2 allele i.e. a dominant (Rh) and a recessive (rh). The Rh gene produce
Rh protein therefore person is called Rh+ve while rh gene is unable to produce
Rh protein so the person is called Rh-ve.
Q. Which
blood group can be transfused to other body’s blood group? Also mention the
reasons.
|
Blood type |
Antigens on RBCs |
Can donate Blood to |
Antibodies in serum |
Can receive blood from |
|
A |
A |
A, AB |
Anti-B |
A, O |
|
B |
B |
B, AB |
Anti-A |
B, O |
|
AB |
A and B |
AB |
None |
A, B, AB, O |
|
O |
None |
A, B, AB, O |
Anti-A and Anti-B |
O |
Q. What is co dominance?
CO-DOMINANACE
‘Co-dominance
or Complete dominance refers to a relationship between two versions of a gene.
Individuals receive one version of a gene from each parent. If both the alleles
are different, the organism is hybrid or Heterozygous. If both the alleles are
same, the organism is pure or Homozygous.’
Which
of the phenomenon of inheritance is there where both factor express in
heterozygous condition?
OR
Q. What is incomplete dominance?
INCOMPLETE DOMINANCE
The
phenomenon of inheritance where both the alleles are heterozygous and their
expressions get blended to produce new phenotype is called incomplete
dominance.
OR
Incomplete dominance is
a form of Gene interaction in which both the alleles of a gene are partially
expressed, often resulting in an intermediate or different phenotype.
EXPERIMENT
Carl
Correns crossed a pure breed ref flowered Japanese 4 O’clock plant with pure
breed white flowered. He got the surprising results that all the plants in F1
generation were Pink in color. He self pollinated the F1 generation.
In
F2 generation, all the three phenotypes were present with the ratio of 2:1:1
i.e. 2 pink, 1 red, 1 white.
CONCLUSION
It
was found that when alleles for red and white were present in the same plant,
neither of them masked the effect of other. Therefore, expression of both the genes
blended to produce phenotype.
Q. What is variation? What are their types?
VARIATION
Genetic
variation is the difference in DNA among individuals or the differences between
populations is called Variation.
TYPES OF VARIATIONS
Following
are the major types of variations.
· Environmental variations
· Heritable variations
· Continuous variations
· Discontinuous variations
Environmental variation
Variations
which are caused by the environment among the members of same species are
called environmental variations.
For
instance; development of muscles in athletes, loss of body parts due to
accident or disease.
Heritable variation OR Genetic Variation
The
variations caused due to the change in genetic material are called genetic
variations or Heritable variations.
Continuous variation
The
differences in characteristics like height, skin color, inteliigence etc are
called continuous variations.
Discontinuous variations
These
are the sharp and sudden changes among the member of same species. They are
purely heritable.
For
instance; Blood group, six fingers in hand or foot etc.
Q. What
are the causes of Variations?
CAUSES OF VARIATIONS
· Mutation
Any alteration in the sequence of DNA is called
Mutation.
OR
The change in the genetic material of an
organism is called mutation.
For instance; Person having six fingers in the
hand.
· Crossing over
The process of mutual sharing of segments of
chromatids between two non sister chromatids of homologous chromosome is called
crossing over.
This crossing over results in the mixing and
segregation of maternal and paternal chromosome. It occurs in Prophase of 1st
meiotic division.
· Independent assortment
of chromosome
In meiosis I, during metaphase, homologous
chromosomes come together in the form of pairs and subsequently segregate
during anaphase I into the daughter cells independently.
OR
Random fertilization of the gametes produced by
meiosis is called independent assortment.
Independent assortment produces a wide variety
of different gametes.
· Fertilization
The different combinations of characters in an
individual are possible as a result of fertilization because the set of alleles
of each gamete is unique and always differ from each other.
Q. Describe Darwinism OR Theory of Natural
Selection.
DARWIN’S THEORY OF
NATURAL SELECTION
Charles
Darwin was an Englishman. He proposed his theory “Theory of Natural Selection’
in his book ‘Origin of Species’. The main postulates of this theory are as
under:
· Over production
· Struggling for existence
· Heritable variation
· Natural selection
Over production
All
organisms possess enormous fertility. They multiply in geometric ratio. Living
organisms reproduce so that their kind continues to exist.
For
instance;
Female
rabbit gives birth to six young ones in one litter and produce four litter in a
year. Six-month rabbit is capable of reproduction.
If
all the rabbits survived and multiplied at this rate, their number would be
very large after some time.
Struggle for existence
Due
to the limited resources, living organisms don’t fight with each other but also
with the member of different species. Due to this struggle, a large number of
organisms are eliminated.
The
struggle for existence can be of three types.
· Intraspecific Struggle: Struggle between the individuals of the same species because of food, shelter, breeding, places etc.
· Interspecific Struggle: Struggle between the
individuals of different species is called interspecific struggle. For
instance; a fox hunts out a rabbit while the fox is preyed upon by a tiger.
· Environmental Struggle: Struggle between the
organisms and environmental factors such as heavy rains, earthquakes, extreme
hot or cold etc.
Heritable
variations
The
differences among the individuals are called variations. Due to the variations,
some individuals would be better adjusted towards the surroundings than the
others.
Those
individuals whose inherited characters fit them best to their environment would
survive and produce more offspring than less fit individuals who will vanish.
Natural
selection
Those
organisms which are provided with favorable variations would survive, because
they are the fittest to face their surroundings while the unfit are destroyed.
Nature selects the fittest individual to survive and reproduce.
Q. What is mean by artificial selection?
ARTIFICIAL SELECTION
The
intentional breeding of plants and animals is called artificial selection.
For
instance; broccoli, Cauli flower, and cabbage were all derived from the wild
mustard plant.
Q. Relate
artificial selection with natural selection.
Artificial
selection is different from natural selection because it describes selection
applied by humans in order to produce genetic change.
