Someone who inherit two recessive albino genes cannot make the black pigment called melanin. Most of us make melanin in our skin, hair and at the back of our eyes. Again, the pattern of inheritance is a simple one just as for PKU and eye colour. The inheritance of this genetic disease is a bit more complicated because it is sex linked. Women normally have two genes for blood clotting, one on each X chromosome.
Men only have one blood clotting gene because they only have one X chromosome.
This gene is not present on a Y chromosome. Some women carry a defective gene for haemophilia. These women are called carriers. Their daughters may be normal or may be carriers. Their sons are either normal or actually have the disease.