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

Explanation

A colour blind man married a woman, who is daughter of a colourblind father and mother homozygous normal vision that means the woman is carrier i.e, the genotype is `X^+ X^-`

Here all women (daughters) are carriers i.e, `X^+ X^-`
A cross between colour blind man a woman from the above result.

From the above cross the probability of their daughters being colour blind is 50% or `1//2` among the daughters or `1//4`among their child.