A woman who is a carrier for the hemophilia gene has a child with a man who does not have hemophilia.Which prediction is correct?

Question

Quizplus · Accepted Answer

The hemophilia gene is carried on the X chromosome, and since women have two X chromosomes, if one of the X chromosomes carries the hemophilia gene, the other X chromosome can compensate for it. Therefore, carriers of the hemophilia gene usually do not have hemophilia. On the other hand, men have only one X chromosome, so if it carries the hemophilia gene, they will have hemophilia. In this case, since the mother is a carrier and the father does not have hemophilia, there is a 50% chance that each son will inherit the hemophilia gene and, therefore, have hemophilia. Since daughters inherit one X chromosome from each parent, there is also a 50% chance that each daughter will inherit the hemophilia gene. However, since carriers of the gene do not typically have the disease, the daughters who inherit the hemophilia gene will be carriers like their mother, rather than having the disease themselves. Therefore, the correct prediction is that half of the sons and none of the daughters will have hemophilia.

A Woman Who Is a Carrier for the Hemophilia Gene