Genetic variability in two Brazilian ethnic groups: a comparison of mitochondrial and protein data.

Sequence data from the first hypervariable segment of the mitochondrial DNA control region of 124 subjects belonging to three African-Brazilian and three Brazilian Indian populations were compared with information related to 12 protein genetic loci from 601 persons living in the same localities. There is high diversity among the mtDNA sites, and the most variable in one ethnic group are not the most variable in the other. No differences in gene diversity between populations within ethnic groups were observed, but the Indians showed a reduced variability. Much more interpopulation variation was observed in the mtDNA data than in the protein set. The relationships obtained for the six populations, however, are the same regardless whether mtDNA or protein loci are considered. African-Brazilians from Porto Alegre and Salvador, situated 3,000 km apart, are more similar to each other than both are to Paredão, despite the geographical proximity between Porto Alegre and Paredão, which are just 50 km apart. The tree topology in relation to the three Indians groups, on the other hand, is that expected when languages, culture, and geography are considered.

Evolutionary relationships between black South American and African populations.

Data related to ten protein genetic loci expressed in blood obtained from four South American black populations were compared with data from seven African countries. Estimates of admixture among South American blacks were revised, and several indexes of gene diversity and genetic distances between the 11 populations were calculated. The admixture values and genetic relationships observed among the South American black communities conform well with those expected on historical grounds, and they show only moderate reductions in genetic diversity.

Protein and hypervariable tandem repeat diversity in eight African-derived South American populations: inferred relationships do not coincide.

We compared data from individuals living in 4 African Venezuelan and 4 African Brazilian communities for 11 protein loci (551 subjects) and 8 hypervariable tandem repeat polymorphisms (252 subjects). There is heterogeneity in diversity within and between the two sets of loci. On the other hand, African-derived Brazilians and Venezuelans do not present marked variability differences between themselves. Although the hypervariable loci show gene diversities that are about four times higher than those obtained from the protein data, they are not more discriminative at the interpopulation level (averages 6% and 4%, respectively). Interpopulation differences do not strictly parallel the geographic distances between the groups, and population relationships obtained from the protein data are not the same as those indicated by hypervariable tandem repeat polymorphisms. Caution is needed in establishing relationships considering just one level of the biological hierarchy.