An Explanation of the Inheritance of Autosomal Dominant Diseases. An autosomal dominant disease usually, but not always, appears in every generation. Sometimes, the expression of a dominant trait may be so slight that it appears not to be present. This is called non-penetrance and explains how a generation can be skipped. Males and females usually are affected equally often and are equally capable of transmitting the disease to further generations.
Transmission is vertical, from parent to child to grandchild on down the line.
Only one parent need be affected and the probability that an affected individual will transmit the disease to an offspring is 50 percent with each pregnancy. In summary, in pregnancies with autosomal dominant diseases, there is a 50 percent chance for recurrence among each offspring, male or female. The disease is transmitted by a single gene derived from one parent, and the defective gene may be inherited from either side of the family. The carrier of a dominant disease usually has the disorder. Examples of Neuromuscular Diseases with Autosomal Dominant Inheritance Facioscapulohumeral muscular dystrophy.