A woman has normal vision although her maternal grandfather

A woman has normal vision although her maternal grandfather (her mother’s father) had red- green colorblindness, a sex-linked recessive trait. Her maternal grandmother and the woman’s own father are assumed to not possess a copy of the mutant allele. The woman marries a man with normal vision although his father was colorblind. What is the probability that the first child of this couple will be colorblind?

Solution

Ans:

The probability that the first child of this couple will be colorblind is 1/8.