Slide show: How genetic disorders are inherited
Illustration of X-linked recessive inheritance with carrier mother
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In an X-linked inheritance pattern, the mutated gene is on the X chromosome. Duchenne muscular dystrophy, color blindness and hemophilia A are examples of X-linked recessive disorders.

For a person to have a recessive disorder, it usually requires two copies of the mutated gene. However, males are affected by a single X-linked recessive gene because they don't have a second X chromosome to override the recessive trait.

A woman who is a carrier of an X-linked recessive disorder has a 25 percent chance of each of the following scenarios: Having an unaffected son, having an affected son, having an unaffected daughter and having an unaffected daughter who also is a carrier.

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