A woman heterozygous for color blindness (an X-linked recessive allele) marries a man with normal color vision. What is the probability that their first child will be color-blind?

Question

Quizplus · Accepted Answer

The probability that their first child will be color-blind is 25 percent. The woman can pass on either the normal vision allele or the color-blind allele, while the man can only pass on the normal vision allele. Sons have a 50% chance of being color-blind, while daughters will not be color-blind. Since there is a 50% chance of having a son, the overall probability is 25%.

A Woman Heterozygous for Color Blindness (An X-Linked Recessive Allele)