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NDA 2023 GAT · General Knowledge · Genetics and Heredity · medium

A woman who is a carrier of haemophilia (an X-linked recessive disorder) marries a normal man. The probability that a given son of the couple is…

Single correct option

A woman who is a carrier of haemophilia (an X-linked recessive disorder) marries a normal man. The probability that a given son of the couple is haemophilic is
  1. A. 1/4
  2. B. 0
  3. C. 1/2
  4. D. 1
Show answer and solution

Answer: (C) 1/2

The mother is XhX and the father XY. A son receives the father's Y and one of the mother's X chromosomes with equal chance, so half of the sons get Xh and are haemophilic. Daughters cannot be affected because they always receive the father's normal X.
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Original question written in the NDA 2023 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake