Figure 2

Autosomal and X-linked patterns of inheritance. In autosomal dominant inheritance, family history typically reveals that the disorder is usually present in every generation, and there is a 50% chance of inheriting the mutation. In autosomal recessive inheritance, the condition appears to "skip" generations. Parents of an affected have a 25% chance of having an affected child and a 50% chance of having a carrier child in each pregnancy. In X-linked dominant inheritance, all daughters of an affected man are affected, sons and daughters of carrier women have a 50% risk of being affected. In X-linked recessive inheritance, there is a 50% chance that each son of a carrier woman will also be affected. No male-male transmission is observed.