Haemophilia is a mainly inherited genetic disorder that prevents blood from clotting. This results in people bleeding more, bruising easier and internal bleeding to happen regularly.
There are 2 main types of haemophilia. Type A and type B. Type A is where there is no factor 8 in blood. Type B is where there isn't enough factor 9 in blood. There are 12 factors and all of the need to connect for blood to clot.
The gene comes from the female parents X chromosome. It is only men affected by this though. The females don't shave the effects even though they are the ones carrying the gene.