Hemophilia is an Xlinked recessive disease A normal woman wh

Hemophilia is an X-linked recessive disease. A normal woman whose father is affected marries a normal man. They decide to have three children. What is the probability that they will have three sons with the disease? 2/3 1/2 1/64 1/32 1/16

Solution

Women have two X chromosomes whereas men have a X and Y chromosome.Haemophilia is a X linked recessive disease,which means that it is passed from mother to son on the X chromosome.If the mother carries the gene for haemophilia on one of her X chromosomes,Each of her sons will have a 50% chance of having haemophilia.

Therefore probability is equal to 1/2.