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Is hemophilia inherited?

Hemophilia is inherited in an X-linked recessive pattern. A condition is considered X-linked when gene mutation that causes it is located on the X chromosome, one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is enough to cause the condition. Since females have two X chromosomes, a mutation must be present in both copies of the gene to cause the hemophilia. Males are affected by X-linked recessive disorders much more frequently than females. A major characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

A female who is a carrier has a 1 in 2 (50 percent) chance to pass on her X chromosome with the gene mutation for hemophilia A or B to a boy who will be affected. She has a 1 in 2 (50 percent) chance to pass on her X chromosome with the normally functioning gene to a boy who will not have hemophilia.

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