Haemophilia In the human body, each cell contains 23 pairs of chromosomes, one of each pair inherited through the egg from the mother, and the other inherited through the sperm of the father. Of these chromosomes, those that determine sex are X and Y. Females have XX and males have XY. In addition to the information on sex, 'the X chromosomes carry determinants for a number of other features of the body including the levels of factor VIII and factor IX.'1 If the genetic information determining the factor VIII and IX level is defective, haemophilia results. When this happens, the protein factors needed for normal blood clotting are effected. In males, the single X chromosome that is effected