Principle Of Inheritance And Variation Question 476

Question: If a boy’s father has haemophilia and his mother has one gene for haemophilia; what is the chance that the boy will inherit the disease [CPMT 1980, 2000; DPMT 1992; AIIMS 1999; Pb. PMT 1999]

Options:

A) 25%

B) 50%

C) 75%

D) 100%

Show Answer

Answer:

Correct Answer: B

Solution:

Chance of a boy inheriting haemophilia solely depends upon the mother’s nature irrespective of his father’s nature.

If mother is heterozygous for disease, chances are 50% and if she is homozygous similarly, then all his sons will inherit the disease.