THE BAGANDA OF EAST AFRICA-A CENTER OF EXCEPTIONALLY HIGH GENETIC DIVERSITY.
          L Louie, C Ginther, M Hammer, E Katongole-Mbidde, and W Klitz, School of Public Health, Univ. California, Berkeley, CA, Lab. Molecular Systematics & Evolution, Univ. Arizona, Tuscon, AZ, Uganda Cancer Inst., Makarere Univ., Kampala, Uganda.
          The Baganda, a Bantu-speaking East African people, are the most common ethnic group in Uganda. We assessed genetic diversity in a sample of 49 Baganda at three distinct genetic systems: HLA, Y chromosome and mitochondria. At each of these systems, high levels of genetic diversity were present, characteristic of many Sub-Saharan populations. HLA typing revealed 17, 8, 12 and 15 alleles at DRB1, DQA1, DQB1 and DPB1, respectively, with homozygosity statistics falling below the neutrality expectation for DRB1, DQA1 and DQB1, and above neutrality for DPB1. Although none of these values is significantly different from the neutrality expectation on its own, this same pattern is consistent with many other populations sampled worldwide. Sequence from mitochondrial hypervariable regions 1 and 2 revealed a mean of 15 pairwise differences within 635 examined nucleotides on 46 individuals. The variation is distributed into three major subgroups, often differing more from one another than from Caucasian or Asian sequences. Bagandan mitochondrial diversity is among the highest examined for any group. Heterozygosity of the 27 males tested for a combination Y chromosome haplotype for the three variable sites was 0.83, distributed in eight distinct haplotypes. These values fall above that found for Asian and European samples. In comparison with other Bantu populations our Baganda sample helps create the impression that common Bantu HLA and mitochondrial haplotypes may not exist, in spite of the fact that the Bantu-speaking peoples are thought to have arisen and expanded across Central and Southern Africa relatively recently. The consistent theme of very high interindividual genetic variation in these people leads to several conclusions: A population bottleneck cannot have occurred in the recent to moderate past. Extensive population admixture cannot be ruled out, in spite of the common linguistic heritage. Finally, HLA variation is consistent with a past history of balancing selection, explainable through pathogen-driven selection