An autosomal dominant gene is an abnormal gene on one of the autosomal (non-sex determining) chromosomes. Because it is dominant, it need only exist in the inherited chromosomes of one parent for it to cause disease. The chances of an autosomal dominant disorder being inherited are 50% if one parent has the gene. Some diseases inherit in this fashion but still affect less than 50% of the offspring; in this case the disease is termed of having incomplete penetrance.

Other forms of inheritance are: autosomal recessive, X-linked and mitochondrial.