Tim Poisal Hemophilia Biology-2nd period Hemophilia Hemophilia is a genetic blood disease, which is characterized by the inability of blood to clot, or coagulate even from minor injuries. This disease is caused by an insufficiency of certain blood proteins, called factors, that participate in blood clotting and often by sudden gene mutation. Therefore, with the absence of factors, the blood clotting process is prolonged. There are different types of hemophilia, hemophilia A and hemophilia B for example. Hemophilia A , the most common form is caused by the lack of factor VIII. In the second most common form of hemophilia, hemophilia B (also known as Christmas disease), factor IX is absent. The condition appears when the person is born. Also, the disease is hereditary, passed on from parent to child. Because of it's genetic makeup, hemophilia is carried by females however those affected are almost always males. In one-third of all cases hemophilia thought to be caused by spontaneous gene mutation with no family history. This is how females are able to be affected by hemophilia. Inheritance is controlled by a recessive sex-linked factor carried by the mother on the X chromosome. There is a fifty percent chance that the sons of a female carrier will have hemophilia. There also is a fifty percent chance that the daughters of a female carrier will be carriers of hemophilia. In addition, all daughters of men with hemophilia are carriers, but his sons are unaffected. Men cannot transmit hemophilia, and female carriers are free of the disease.