Hapsburg family tree

Hapsburg family tree: inheritance of the "Hapsburg Lip"
Mandibular prognathism is the name of a heritable genetic conditions where growth of the maxilla (upper jaw) is retarded with respect to the the mandible (lower jaw), which results in a projecting chin, rolled-out lower lip, and a crossbite of the incisors. The phenomenon is known as the 'Hapsburg Lip' because of its occurrence in multiple generations of members of the European royal House of Hapsburg, as documented in their portraits over 200 years [above]. The trait is inherited as a single-gene autosomal dominant with incomplete penetrance (~ 0.90), and shows up frequently because of extensive intermarriage between different branches of the family. extensive inbreeding. Queen Isabella I and King Ferdinand II of Castile & Aragon, Columbus' patrons on his voyages to America, are early case. Kings Charles II and Philip IV of Spain, and Leopold of Austria, have particularly prominent cases. It may be assumed that portrait artists 'improved' the appearance of their subjects in some cases.

HOMEWORK: Redraw the portrait gallery above as a pedigree. Show that inheritance is consistent with an autosomal recessive. (Note that only affected persons are shown: this causes an ascertainment bias).

Text material © 2021 by Steven M. Carr