Human transferrin (Tf) and group-specific component (Gc) subtypes in Tunisia

Summary Simultaneous subtyping of two genetic markers—group-specific component (Gc) and transferrin (Tf)—by electrofocusing enabled us to compute the following gene frequencies for the Tunisian population: Gc ^IS .0.525; Gc ^IF , 0.260; Gc ², 0.215; Tf ^CI , 0.770; Tf ^C2 , 0.215; Tf ^D1 , 0.015.The frequencies of Tf ^D , Tf ^C2 , and Gc ¹ are higher than those found in Caucasoid populations and can be explained by Negroid contribution. A selective advantage related to the metabolic role of this vitamin D-binding protein does not seem very likely for any particular Gc type or subtype. It is postulated that the differences in the frequencies of the Gc alleles might be related to selective advantage for genes belonging to other genetic systems originally closely linked to either Gc ¹ or to Gc ² alleles.This work was supported in part by the Faculté de Pharmacie et de Médecine Dentaire of Monastir and by a grant from the Ambassade de France in Tunisia