Question

A male carries a recessive mutation on the X chromosome that causes hemophilia, a blood clotting disorder. He marries a female who is phenotypically normal, but whose father had hemophilia. Suppose they have a child. What is the probability that the child will have hemophilia

Answer 1

Answer:

Explanation:

Hemophilia is a X linked recessive genetic disorder caused by low amount of clotting factors. Hence, it becomes difficult to stop bleeding in case of an an injury and takes more time to clot. Here,

c= recessive allele for hemophilia gene

C= dominant allele for hemophilia gene

Genotype of male: XcY since he carries the recessive allele for hemophilia trait

Genotype of female: XCXc. She does not have hemophilia but her father had hemophilia so she she must have received one X chromosome from him and hence is a carrier for hemophilia.

Their children:

XcY  X   XCXc = XCXc,  XcXc,  XCY,  XcY

Out of resultant genotypes 2 out of 4 i.e. XcXc and XcY show hemophilia trait hence there is 50% probability that the child will have hemophilia.