question_answer

A man whose father was colourblind marries a woman, who had a colourblind mother and normal father. What percentage of male children of this couple will be colourblind?

A) 25%                             

B) 0%    

C) 50%     

D) 75%

Correct Answer: C

Solution :

[c] Colour blindness is a sex-linked recessive genetic disorder involving the X-chromosome. Thus, according to the situation given in the question, a man whose father was colourblind will be, normal, i.e. XY and a woman whose mother was colourblind and father was normal is a carrier, i.e. XX. Thus, when marriage happens between two such individuals percentage of a male child to be colourblind is 50% (this can be easily observed from the cross given below)