Why are women carriers for hemophilia? Why do their sons, but not their daughters get the disease?
Their daughters can! This is because females have two X chromosomes while males have only one, so the defective gene is guaranteed to manifest in any male who carries it. Because females have two X chromosomes and haemophilia is rare, the chance of a female having two defective copies of the gene is very low, so females are ALMOST exclusively asymptomatic carriers of the disorder. Haemophilia A (clotting factor VIII deficiency) is the most common form of the disorder, occurring at about 1 in 5,000–10,000 male births 1 in 10,000 x 10,000 is very unlikely.
