Why are human females rarely haemophilic?

Explanation

Haemophilia is an X-linked recessive disease. It is also known as bleeder.s disease, because in the event of an injury, the blood fails to coagulate. Inheritance of haemophilia follows the criss-cross pattern. The females have haemophilic allele on a single X-chromosome, thus they do not produce haemophilic phenotype. Such females are called as carriers of the haemophilic allele. The female parent transmits one each of her X-chromosomes to her sons and daughters in equal proportion. Thus, the mother of a carrier haemophilic female has to be atleast a carrier and father to be a haemophilic. Thus, human females having two defective copies of the gene is very rare.