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Principles of Inheritance and Variation · Question 125

AIPMT 2005MCQEasy📈 Topic in 50% papers+4−1
1

A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance do you suggest for this disease?

  1. Autosomal dominant
  2. Sex-linked recessive
  3. Sex-linked dominant
  4. Sex-limited recessive

Answer

(2) Sex-linked recessive

Solution

∵ Both parents are normal but some children are affected ⇒ the trait is recessive (an autosomal dominant trait would show in a parent).

∵ Only sons are affected and no daughter ⇒ the gene is X-linked.

⇒ Mother is a carrier ( XHXh), father normal ( XHY): sons receive Xh with 50% chance and are affected; daughters get the normal X from the father and are not affected.

∴ As per NCERT (like haemophilia and colour blindness), this is sex-linked recessive inheritance.

Answer: (2)

AIPMT 2005

Keep practising — Principles of Inheritance and Variation

2

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

  1. Superfemaleness
  2. Turner's syndrome
  3. Triploidy
  4. Down's syndrome
AIPMT 2005
3

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
AIPMT 2005
4

Which of the following is not a hereditary disease?

  1. Cretinism
  2. Cystic fibrosis
  3. Haemophilia
  4. Thalassemia
AIPMT 2005
5

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.
AIPMT 2005
6

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
AIPMT 2005
7

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
AIPMT 2004
8

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
AIPMT 2004
9

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
AIPMT 2004
10

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
AIPMT 2004
11

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
AIPMT 2004

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