Question

A man known to be a victim of haemophilia marries a normal woman whose father was known to be a bleeder. Then it is expected that:

• A. All their children will be bleeders
• B. Half of their children will be bleeders
• C. One-fourth of their children will be bleeders
• D. None of their children will be a bleeder

Answer 1

The correct option is B Half of their children will be bleeders

Since the man is haemophilic, his genotype will be $X^{H}Y$.
Since the father of the woman is bleeder (haemophilic), the woman will be carrier for haemophilia and hence, her genotype will be $X^{H}X$.
The cross can be represented as shown in the figure.


Hence, out of their four children, one boy and one girl is bleeder i.e., they are haemophilic. Thus, half of their children will be bleeders.