Dominant inheritance (not sex-linked)

A disease trait determined by dominant allele affects both sexes and appears as many times among men as among women. It manifests in heterozygote as well as in homozygote except the latter is usually much more serious case and can be lethal. Disease is usually present in every generation and health parents do not transmit it to their offspring. However there is an exception called lack of penetrance when a person carries mutant gene and do not demonstrate the effect. Such individual, just like ill heterozygotes, have a 50% chance of passing the mutant gene to the child. Disease would only skip one generation in this case.

Usually dominantly inherited diseases affect structural, transporting or receptor proteins and are less severe than the recessive ones. Still there are several that are very serious and prevent ill persons from having offspring (mutant gene is not further transmitted). In this case the disease is effect of new mutation. For some of dominantly inherited diseases the risk of new mutation increases with the age of the father.