Principles of Inheritance and Variation

Haemophilia is more commonly seen in human males than in human females because -

1. This disease is due to an X-linked dominant mutation
2. This disease is due to a Y-linked recessive mutation
3. This disease is due to an X-linked recessive mutation
4. A greater proportion of girls die in infancy

Which of the following is not a hereditary disease?

1. Cretinism
2. Cystic fibrosis
3. Haemophilia
4. Thalassemia

A woman with normal vision, but whose father was colour blind, marries a colour blind man. Suppose that the fourth child of this couple was a boy. This boy -

1. May be colour blind or may have normal vision
2. Must have normal colour vision
3. Must be colour blind
4. Will be partially colour blind since he is heterozygous for the colour blind mutant allele.

A woman with 47 chromosomes due to three copies of chromosome 21 is characterized by

1. triploidy
2. Down’s syndrome
3. superfemaleness
4. Turner’s syndrome

In a plant, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). If a plant with RRTt genotype is crossed with a plant that is rrtt

1. 75% will be tall with red fruit
2. 25% will be tall with red fruit
3. 50% will be tall with red fruit
4. All the offspring will be tall with red fruit

A male human is heterozygous for autosomal genes A and B and is also hemizygous for hemophilic gene h. What proportion of his sperms will be abh?

1. 1/16
2. 1/32
3. 1/8
4. 1/4

Lack of independent assortment of two genes A and B in fruit fly Drosophila is due to

1. Linkage
2. Recombination
3. Repulsion
4. Crossing over

One of the parents of a cross has a mutation in its mitochondria. In that cross, that parent is taken as a male. During segregation of F2 progenies that mutation is found in -

1. 50% of the progenies
2. 1/3 of the progenies
3. None of the progenies
4. All the progenies

A normal woman, whose father was colour-blind is married to a normal man. The sons would be :-

1. All colour-blind
2. 75% colour-blind
3. All normal
4. 50% colour-blind

The recessive genes located on X-chromosomes in humans are always -

1. Expressed in females
2. Sub-lethal
3. Expressed in males
4. Lethal