Abstract
This lecture lays the historical and methodological foundations for answering a fundamental question : how much of our biological diversity is attributable to genetics ? Following a retrospective of Mendel's work on heredity, it will look at examples of monogenic diseases with high heritability, such as hemophilia. The discussion will then focus on the notions of penetrance and expressivity, illustrated by examples such as Huntington's disease. The lecture will also introduce heritability as a statistical concept and discuss complex traits with variable heritability, as well as the evolution of the concept ofgenetic architecture : from the monogenic to the omnigeneic model, and from the impact of frequent mutations on diseases to that of rare mutations.
