Chapter-5 Principles of Inheritance and Variation

Discuss in detail the contributions of Morgan and Sturvant in the area
of genetics.

A normal visioned woman, whose father is colour blind, marries a normal
visioned man. What would be probability of her sons and daughters to
be colour blind? Explain with the help of a pedigree chart.

a. In humans, males are heterogametic and females are homogametic.
Explain. Are there any examples where males are homogametic
and females heterogametic?
b. Also describe as to, who determines the sex of an unborn child?
Mention whether temperature has a role in sex determination.

In a plant tallness is dominant over dwarfness and red flower is dominant
over white. Starting with the parents work out a dihybrid cross. What is
standard dihybrid ratio? Do you think the values would deviate if the
two genes in question are interacting with each other?

It is said, that the harmful alleles get eliminated from population over a
period of time, yet sickle cell anaemia is persisting in human population.
Why?

With the help of an example differentiate between incomplete dominance
and co-dominance.

What is artificial selection? Do you think it affects the process of natural
selection? How?

What is recombination? Discuss the applications of recombination from
the point of view of genetic engineering.

How do genes and chromosomes share similarity from the point of view
of genetical studies?

Discuss why Drosophila has been used extensively for genetical studies.

Discuss why Drosophila has been used extensively for genetical studies.

If a father and son are both defective in red-green colour vision, is it
likely that the son inherited the trait from his father? Comment.

Why is the frequency of red-green colour blindness is many times higher
in males than that in the females?

In peas, tallness is dominant over dwarfness, and red colour of flowers
is dominant over the white colour. When a tall plant bearing red flowers
was pollinated with a dwarf plant bearing white flowers, the different
phenotypic groups were obtained in the progeny in numbers mentioned
against them:
Tall, Red = 138
Tall, White = 132
Dwarf, Red = 136
Dwarf, White = 128

What are the characteristic features of a true-breeding line?

A plant with red flowers was crossed with another plant with yellow
flowers. If F1 showed all flowers orange in colour, explain the inheritance.

How was it concluded that genes are located on chromosomes?

What is Down’s syndrome? Give its symptoms and cause. Why is it that
the chances of having a child with Down’s syndrome increases if the age
of the mother exceeds forty years?

Can a child have blood group O if his parents have blood group ‘A’ and
‘B’. Explain.

In a Mendelian monohybrid cross, the F2 generation shows identical
genotypic and phenotypic ratios. What does it tell us about the nature
of alleles involved? Justify your answer.

How does a mutagen induce mutation? Explain with example.

Even if a character shows multiple allelism, an individual will only have
two alleles for that character. Why?

Discuss the genetic basis of wrinkled phenotype of pea seed.

In our society a woman is often blamed for not bearing male child. Do
you think it is right? Justify.

A, B, D are three independently assorting genes with their recessive alleles
a, b, d, respectively. A cross was made between individuals of Aa bb DD
genotype with aa bb dd. Find out the type of genotypes of the offspring
produced.

For the expression of traits genes provide only the potentiality and the
environment provides the opportunity. Comment on the veracity of the
statement.

In a monohybrid cross of plants with red and white flowered plants,
Mendel got only red flowered plants. On self-pollinating these F1 plants
got both red and white flowered plants in 3:1 ratio. Explain the basis
of using RR and rr symbols to represent the genotype of plants of
parental generation.

How are alleles of particular gene differ from each other? Explain its
significance.

“Genes contain the information that is required to express a particular
trait.” Explain.

In order to obtain the F1 generation Mendel pollinated a pure-breeding
tall plant with a pure breeding dwarf plant. But for getting the F2
generation, he simply self-pollinated the tall F1 plants. Why?

A person has to perform crosses for the purpose of studying inheritance
of a few traits / characters. What should be the criteria for selecting the
organisms?

Enlist the steps of controlled cross pollination. Would emasculation be
needed in a cucurbit plant? Give reasons for your answer.

Do you think Mendel’s laws of inheritance would have been different if
the characters that he chose were located on the same chromosome

What is the cross between the progeny of F1 and the homozygous
recessive parent called? How is it useful?

A dihybrid heterozygous round, yellow seeded garden pea (Pisum sativum)
was crossed with a double recessive plant.
(i) What type of cross is this?
(ii) Work out the genotype and phenotype of the progeny.
(iii) What principle of Mendel is illustrated through the result of this cross?

In Mendel’s breeding experiment on garden pea, the offspring of F2
generation are obtained in the ratio of 25% pure yellow pod, 50% hybrid
green pods and 25% green pods State (i) which pod colour is dominant
(ii) The Phenotypes of the individuals of F1 generation. (iii) Workout the
cross.

Explain the cause of Klinefelter’s syndrome. Give any four symptoms shown
by sufferer of this syndrome.

A woman with O blood group marries a man with AB blood group
(i) work out all the possible phenotypes and genotypes of the progeny.
(ii) Discuss the kind of dominance in the parents and the progeny in this
case.

Differentiate between point mutation and frameshift mutations.

Mention four reasons why Drosophila was chosen by Morgan for his
experiments in genetics.

The human male never passes on the gene for haemophilia to his son.
Why is it so?

Mention two differences between Turner’s syndrome and Klinefelter’s
syndome.

Identify the sex of organism as male or female in which the sex
chromosome are found as
(i) ZW in bird (ii) XY in Drosophila (iii) ZZ in birds. (iv) XO in grasshopper.

A test is performed to know whether the given plant is homozygous
dominant or heterozygous. Name the test and phenotypic ratio of this test
for a monohybrid cross.

A haemophilic man marries a normal homozygous woman. What is the
probability that their daughter will be haemophilic?

Name the base change and the amino acid change, responsible for sickle
cell anaemia.

Name any one plant that shows the phenomenon of incomplete dominance
during the inheritance of its flower colour.

Give any two reasons for the selection of pea plants by Mendel for his
experiments.

A dihybrid heterozygous tall & yellow pea plant was crossed with double
recessive plant.
(i) What type of cross is this?
(ii) Work out the genotype & phenotype of progeny
(iii) What principle of Mendel is illustrated through result of this cross?

A smooth seeded & red – flowered pea plant (SsRr) is crossed with smooth
seeded & white flowered pea plant (Ssrr). Determine the phenotypic &
genotypic ratio in f1 progeny?

How sex is determined in human brings?

What are multiple alleles? Give an example?

What is pedigree Analysis? How is it useful?

Give the chromosomal constitution & related sex in each of the following :-
i) Turner syndrome
ii) Klinefilter syndrome

Name any one plant & its feature that shows the phenomena of incomplete
dominance?

What was the total number of varieties of garden pea which Mendel had taken to
start his experiment?

What is mutagen? Give an example?

In an cross made between a hybrid tall & red plant (TtRr) with dwarf & white
flower (ttrr). What will be the genotype of plants in F1 generation?

A man with AB blood group marries a woman with O group blood.
(i) Work out all the possible phenotypes & genotypes of the progeny.
(ii) Discuss the kind of domination in parents & progeny in this case?

The map distance in certain organism between genes A & B is 4 units,
between B & C is units, & between C & D is 8 units which one of these gene
paves will show more recombination frequency? Give reason.

How is the child affected if it has grown from the zygote formed by an XX-egg
fertilized by Y-carrying sperm? What do you call this abnormality?

Why do sons of haemophilic father never suffer from this trait?

What is a test cross?

Which one change is the cause of sickle – cell anaemia ?

What genetic principle could be derived from a monohybrid cross?

In dogs, barking trait is dominant over silent trait & erect ears are dominant
over drooping ears. What is the expected phenotypic ratio of offspring when
dogs heterozygous for both the traits are crossed?

A red eyed male fruitfly is crossed with white eyed female fruitfly. Work out
the possible genotype & phenotype of F1 & F2 generation. Comment on the
pattern of inheritance in this cross?

In Antirrhinum majus a plant with red flowers was crossed with a plant
with white flowers. Work out all the possible genotypes & phenotypes of F1
& F2 generations comment on the pattern of inheritance in this case?

How will you find out whether a given plant is homozygous or
heterozygous?

Which law of Mendel is universally accepted? State the law?

Give any two similarities between behavior of genes (Mendel’s factor)
during inheritance & chromosomes during cell division.

What is meant by aneuploidy?

Name one trait each in humans & in drosophila whose genes are located on
sex chromosome.

Name the phenomena that occur when homologous chromosomes do not
separate during meiosis.

Mention any two autosomal genetic disorders with their symptoms.

Who had proposed the chromosomal theory of inheritance?

What is point mutation? Give one example.

Explain the following terms with example

(a) Co-dominance

(b) Incomplete dominance

A child has blood group O. If the father has blood group A and mother

blood group B, work out the genotypes of the parents and the possible

genotypes of the other offsprings

How is sex determined in human beings?

What is pedigree analysis? Suggest how such an analysis, can be useful.

What is pedigree analysis? Suggest how such an analysis, can be useful.

Briefly mention the contribution of T.H. Morgan in genetics

Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in F1 generation for a dihybrid cross?

When a cross in made between tall plants with yellow seeds (TtYy) and tall plant with green seed (TtYy), what proportions of phenotype in the offspring could be expected to be

(a) Tall and green.

(b) Dwarf and green.

Using a Punnett square, work out the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.

Define and design a test - cross?

Explain the Law of Dominance using a monohybrid cross.

A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced?

Differentiate between the following -

(a) Dominance and Recessive

(b) Homozygous and Heterozygous

(c) Monohybrid and Dihybrid

Mention the advantages of selecting pea plant for experiment by Mendel.