A study of Gm allotypes and immunoglobulin heavy gamma IGHG genes in Berbers, Arabs and sub-Saharan Africans from Jerba Island, Tunisia

The Gm polymorphism of human IgG immunoglobulins was investigated in three different ethnic groups - Arabs, Berbers and 'dark-skinned people' - on Jer ba Island, Tunisia. The genetic relationships among these groups and severa l populations from North Africa, sub-Saharan Africa, west Asia and Europe w ere analysed by principal coordinate analysis, Fst significance testing, an d analysis of molecular variance based on haplotype frequencies. The result s revealed a non-significant genetic differentiation between Arabs and Berb ers from Jerba. However, the Jerbian population of sub-Saharan African orig in was close to Ethiopians. Gene flow among the three Jerbian populations, as well as an East African origin of the dark-skinned individuals, is propo sed to account for the observed genetic pattern. However, the genetic diver sity observed among the different Tunisian populations did not show any sig nificant correlation with either geographic or linguistic differentiation. A preliminary analysis of the restriction fragment length polymorphism of t he IGHG genes in Arabs and Berbers from Jerba confirmed the close genetic r elationship between the two populations. However, it also indicated a lower level of genetic diversity in the Berbers, which may be explained by more rapid genetic drift due to longer isolation on the island.