Question

A man whose father was colour blind marries a woman who had a colour blind mother and normal father. What percentage of male children of this couple will be colour blind
A. 0.25
B. 0
C. 0.5
D. 0.75

Answer 1

Correct Answer - A
As colour blindness is a sex-linked recessive genetic disorder, for it is present at X-chromosome. Thus, according the gene to the situation given in the question, a man whose father was colour blind (will be, i.e. XY normal) marries a woman whose mother was colourblind and father was normal (i.e. this woman will be a carrier) according to the cross given below.

Thus, when marriage will happen between a normal man and a carrier woman. in that case percentage of a male child to be colourblind is 25% (this can be easily observed from the cross given below)