Hemophilia is a sex-linked disorder that is caused by a recessive allele. If the mom is a carrier of hemophilia and the dad doesn't have hemophilia, what is the chance that they will have a child with hemophilia?
A. 50% chance
B. 75% chance
C. 100% chance
D. 25% chance
D. 25% chance
Explanation: In this scenario, the mother is a carrier of hemophilia, which means she has one normal allele and one allele for hemophilia. The father does not have hemophilia, so he must have two normal alleles.
When they have a child, there is a 50% chance that the child will inherit the mother's normal allele and a 50% chance that the child will inherit the mother's hemophilia allele. Therefore, there is a 25% chance (50% x 50%) that the child will inherit two hemophilia alleles and have hemophilia.