Distribution of Serum Group-specific Components (Gc) in Afghanistan, Korean, Nigerian and Israeli Populations

Abstract

SINCE the discovery of the serum Gc polymorphism by Hirschfeld¹ genetic investigations have confirmed that the three common Gc phenotypes, designated Gc 1–1, Gc 2–1, and Gc 2–2, are controlled by two autosomal co-dominant alleles Gc¹ and Gc². Two genetic variants, one in a Chippewa Indian population, the other in a population of Australian Aborigines, have been recognized and called Gc Chippewa and Gc Aborigine, respectively³. In addition, abnormal patterns have been seen rarely in certain samples of serum from Caucasians (Gc X), and from Negroes (Gc Y)^4–6. In spite of considerable progress in the isolation and chemical characterization of the Gc components⁷, no biological activity has been found thus far and nothing is known of the nature of the selective pressures operating on this polymorphic system. Nevertheless, striking differences have been found in the gene frequency of the Gc protein in a large number of different population and ethnic groups. Low Gc² frequencies are found in the Navajo Indians (0.023), the Nigerian Fulani (0.050), the Nigerian Habe (0.073) and the Negroes of Bandei (0.096), Congo (0.095), Baganda (0.093) and New York City (0.108). In contrast Gc² frequencies are high in a group of Ashkenazi Jews living in Israel (0.338), in Bombay Indians (0.306) and in Xavante Indians of the Brazilian Mato Grosso (0.670) (refs. 7 and 8). All other population groups, including European, Japanese and Arabs, have levels which fall within the intermediate range of 0.12–0.29, apart from an isolated and probably inbred community living on Kokar, an island in the archipelago of Åland between Finland and Sweden (0.385) (ref. 9).