You are a genetic counselor, and a couple comes to you with concerns that if they have a child together, he or she could have hemophilia. Neither of them has hemophilia, but the woman's biological father did have an X-linked recessive form of hemophilia. How should you advise them?

Question

Quizplus · Accepted Answer

Hemophilia is an X-linked recessive disorder. The woman, having a father with hemophilia, is a carrier (XHXh). The man, without hemophilia, has a normal X chromosome (XHY). Their sons (XhY from the mother and XHY from the father) have a 50% chance of having hemophilia depending on whether they inherit the Xh chromosome from their mother. Their daughters (XHXh or XHXH) have a 50% chance of being carriers, depending on whether they inherit the Xh chromosome from their mother or the normal XH from her.

You Are a Genetic Counselor, and a Couple Comes to You