Principles of Inheritance and Variation


What is point mutation? Give one example.


Mutations arising due to change in single base pair of DNA is called point mutation. Eg., sickle cell anaemia, haemophilia.


Principles of Inheritance and Variation

Q 1.

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

Q 2.

What is point mutation? Give one example.

Q 3.

Explain the following terms with example
(b)Incomplete dominance

Q 4.

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?

Q 5.

Mention any two autosomal genetic disorders with their symptoms.

Q 6.

The pedigree chart given below shows a particular trait which is absent in parents but present in the next generation irrespective of sexes. Draw your conclusion on the basis of the pedigree.

Q 7.

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

Q 8.

How was it concluded that genes are located on chromosomes?

Q 9.

Discuss why Drosophila has been used extensively for genetical studies.

Q 10.

Explain the Law of Dominance using a monohybrid cross.

Q 11.

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

Q 12.

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?

Q 13.

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

Q 14.

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

Q 15.

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

Q 16.

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

Q 17.

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

Q 18.

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

Q 19.

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

Q 20.

Mention the advantages of selecting pea plant for experiment by Mendel

Q 21.

Discuss the genetic basis of wrinkled phenotype of pea seed.

Q 22.

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

Q 23.

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

Q 24.

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

Q 25.

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

Q 26.

Who had proposed the chromosomal theory of the inheritance?

Q 27.

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

Q 28.

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?

Q 29.

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

Q 30.

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?

Q 31.

A child has blood group O. If the father has blood group A and mother of blood group B, work out the genotypes of the parents and the possible genotypes of the other off springs.

Q 32.

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

Q 33.

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 off spring produced.

Q 34.

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

Q 35.

Define and design a test-cross.

Q 36.

How is sex determined in human beings?

Q 37.

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.

Q 38.

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.

Q 39.

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 geno type of plants of parental generation.

Q 40.

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

Q 41.

How does a mutagen induce mutation? Explain with example.

Q 42.

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?

Q 43.

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.

Q 44.

(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.

Q 45.

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?

Q 46.

Define aneuploidy. How is it different from polyploidy? Describe the individuals having the following chromosomal abnormalities.
a. Trisomy of 21st chromosome
b. XXY
c. XO

Q 47.

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
Mention the genotypes of the two parents and of the four offspring types.

Q 48.

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

Q 49.

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

Q 50.

Differentiate between the following –
(a)Dominance and Recessive
(b)Homozygous and Heterozygous
(c)Monohybrid and Dihybrid.