Question

A woman who is a carrier for x-linked recessive hemophilia (she does not have the disease) marries a man who does not have hemophilia. they have a daughter, named angela, who does not have the disease. angela marries george, who also does not have hemophilia. angela and george have a son named robbie. what is the chance that robbie will have hemophilia?

Answer 1

The answer is 25%

Hemofilia is inherited by x-linked recessive pattern. Only woman could become recessive since woman has two x genes but man only has one.

The first generation is a carrier woman with normal man. The chance of their daughter to inherit the defect gene from her mother would be 50%. Then the daughter(angela) marries a normal man (George). The chance of Angela giving defect gene also 50%. The resultant chance would be: 50%*50%= 25%