Principles of Medical Genetics

The Mendelian Disorders The most comprehensive catalogue of Mendelian phenotypes is that assembled by McKusick.⁵To date, 2336 Mendelian phenotypes have been described. Of these, 1218 are autosomal dominant, 947 are autosomal recessive, and 171 are X-linked, almost all X-linked recessive. Approximately half the entries in each of these three categories are well established, whereas the evidence for the remaining half is less firm. Despite the great advances in molecular genetics, it is still advantageous to define the Mendelian pattern of inheritance of disorders in terms of the genetic constitution of the affected individuals. For example, since blood both from.