Question

A colour blind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their grandson becoming colour blind

• A. 0.5
• B. 1
• C. Nil
• D. 0.25.

Answer 1

The correct option is C Nil

Genotype of colour blind man = XcY

Genotype of normal female = XX

Thus, the cross between these two individuals will give the possible combinations and from the Punnett Square it is evident that none of the sons are victims of the disease. So none of them will be colour blind.

Male/Female	Xc	Y
X	XXc	XY
X	XXc	XY

So the correct option is 'Nil'.