Founder effect in beta-thalassaemia in Portneuf, Québec.

The genealogies of seven individuals with beta-thalassaemia minor carrying the (beta+IVS-1, nt110) mutation were reconstructed to determine the origin of the mutation in the French Canadian population of Portneuf County. A set of 55 ancestors common to all seven carriers was defined. These founders included 38 born in Europe of whom 34 came from 13 different regions of France and in particular from Languedoc (2 ancestors), a French province along the Mediterranean sea in which the mutation is still present. Descendants of these two individuals settled in Portneuf County where the gene frequency increased due to a high level of endogamy. However, present results cannot exclude a possibility that the (beta+IVS-1, nt110) mutation was introduced into the French Canadian population by settlers originating from a non-malarial region of France. The beta-thalassaemia gene has since spread from Portneuf County over the last century.