One form of hemophilia is caused by a sex-linked recessive gene.Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia.What is the probability that they will have a daughter with hemophilia? (Note: In this problem,you must include the probability of having a daughter in your computation of the final probability.)

Question

Quizplus · Accepted Answer

Since hemophilia is a sex-linked recessive trait, the father with hemophilia will pass on the recessive allele to all of his daughters (since he only passes on a Y chromosome to his sons). The normal woman is a carrier of the recessive allele since her father had hemophilia. Therefore, the probability of having a daughter with hemophilia is 1/4, or 25%. To find the overall probability, we need to multiply the probability of having a daughter (1/2) by the probability of having a daughter with hemophilia (1/4):
1/2 x 1/4 = 1/8
So the probability of this couple having a daughter with hemophilia is 1/8 or 12.5%. Therefore, the best choice is option C, 1/4.

One Form of Hemophilia Is Caused by a Sex-Linked Recessive