Causes
Hemophilia is caused by a faulty gene inherited from one or both parent. It is called an inherited sex-linked recessive gene. The gene is located on the X chromosome.
Females carry two copies of the X chromosome. If the faulty gene is only on one X, the normal gene on the second X will take over. As a result, they will not get the disease. Instead they are carriers of the gene. The risk for their male offspring to inherit the gene is 1 in 2 or 50%. The chance that their female offspring will inherit the gene is also 50%. These offspring will be carriers like their mothers.
It is possible for a female to have hemophilia. For this to happen she must inherit the faulty gene from both her mother and her father.
Males carry only one X chromosome. If they get the faulty gene the disease will develop.
Genetic Outcome Possibilities

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Hemophilia A