Haemophilia is a X-linked genetic disorder, which means that it shows criss cross inheritance. Like most recessive sex-linked X chromosome disorders, haemophilia is more likely to occur in males than females. This is because females have two X chromosomes (XX),while males have only one (XY), so the defective gene is guaranteed to manifest in any male who carries it. As females having two defective copies of the gene is very rare
Haemophilia impairs the body's ability to control blood clotting and coagulation.
