Explain the pattern of inheritance of haemophilia in humans. Why is the possibility of a human female becoming a haemophilic is extremely rare? Explain.

Explanation

A woman has two X chromosomes, If only one X-chromosome bears an allele for haemophilia, its dominant allele present on the other X-chromosome will not allow the expression of recessive haemophilia allele since haemophilia is a sex linked recessive disease, Such females will be normal but are called carriers for hemophilia gene. This disease occurs mostly in the males because they have one X-chromosome (XY) only Haemophilia is a disorder of the blood which prevents its clotting due to whence of anti-haemophilic globulin. The patient will continue to bleed even from a minor skin cut and as a result of continuous bleeding, he or she may die due to excessive blood loss.