DIFFERENT GENETIC COMPONENTS IN THE ETHIOPIAN POPULATION, IDENTIFIED BY MTDNA AND Y-CHROMOSOME POLYMORPHISMS

Seventy-seven Ethiopians were investigated for mtDNA and Y chromosome- specific variations, in order to (1) define the different maternal and paternal components of the Ethiopian gene pool, (2) infer the origins of these maternal and paternal lineages and estimate their relative c ontributions, and (3) obtain information about ancient populations liv ing in Ethiopia. The mtDNA was studied for the RFLPs relative to the s ix classical enzymes (HpaI, BamHI, HaeII, MspI, AvaII, and HincII) tha t identify the African haplogroup L and the Caucasoid haplogroups I an d T. The sample was also examined at restriction sites that define the other Caucasoid haplogroups (H, U, V, W, X, J, and K) and for the sim ultaneous presence of the DdeI(10394) and AluI(10397) sites, which def ines the Asian haplogroup M, Four polymorphic systems were examined on the Y chromosome: the TaqI/12f2 and the 49a,f RFLPs, the Y Alu polymo rphic element (DYS287), and the sY81-A/G (DYS271) polymorphism. For co mparison, the last two Y polymorphisms were also examined in 87 Senega lese previously classified for the two TaqI RFLPs. Results from these markers led to the hypothesis that the Ethiopian population (1) experi enced Caucasoid gene flow mainly through males, (2) contains African c omponents ascribable to Bantu migrations and to an in situ differentia tion process from an ancestral African gene pool, and (3) exhibits som e Y-chromosome affinities with the Tsumkwe San (a very ancient African group). Our finding of a high (20%) frequency of the ''Asian'' DdeI(1 0394)AluI(10394), (++) mtDNA haplotype in Ethiopia is discussed in ter ms of the ''out of Africa'' model.