Hemophilia is caused by several genetic factors;one,a recessive allele of an X-linked gene,is the subject of this problem.Assume that a man with hemophilia marries a normal woman whose father had hemophilia.What is the probability that they will have a daughter with hemophilia?

Question

Quizplus · Accepted Answer

A man with hemophilia must have the affected X allele, which he inherited from his mother since it is X-linked. A normal woman whose father had hemophilia must be heterozygous for the affected allele since she is a carrier. When they have children, their daughters will inherit one X chromosome from each parent. The daughter has a 50% chance of inheriting the affected X allele from her father and a 50% chance of inheriting the normal X allele from her mother. Therefore, the probability of their daughter having hemophilia is (1/2)x(1/2) = 1/4.

Hemophilia Is Caused by Several Genetic Factors;one,a Recessive Allele of an X-Linked