Genetic diversity of two African and sixteen South American populations determined on the basis of six hypervariable loci.

A total of 582 individuals (1,164 chromosomes) from two African, eight African-derived South American, five South American Amerindian, and three Brazilian urban populations were studied at four variable number of tandem repeat (VNTR) and two short tandem repeat (STR) hypervariable loci. These two sets of loci did not show distinct allele profiles, which might be expected if different processes promoted their molecular differentiation. The two African groups showed little difference between them, and their intrapopulational variation was similar to those obtained in the African-derived South American communities. The latter showed different degrees of interpopulation variability, despite the fact that they presented almost identical average degrees of non-African admixture. The F(ST) single locus estimates differed in the five sets of populations, probably due to genetic drift, indicating the need to consider population structure in the evaluation of their total variability. A high interpopulational diversity was found among Amerindian populations in relation to Brazilian African-derived isolated communities. This is probably a consequence of the differences in the patterns of gene flow and genetic drift that each of these semi-isolated groups experienced.

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.

The age at menarche in Carabobo, Venezuela with a note on the secular trend.

A study of the age at menarche was conducted in the state of Carabobo as part of Project Venezuela, a National Human Growth, Nutrition and Family Survey. The study was performed during 1978 on a cross-sectional random stratified sample which included 955 girls between the ages of 9 and 20 years. Data were collected using the status quo method. The median age at menarche was estimated by logits at 12.68 0.08 for all socio-economic groups. Sexual maturation occurred earlier in girls from stratum III and later in those from strata IV and V; 12.34 0.11, 12.59 0.11, and 12.86 0.12, respectively. Small sample size did not permit comparisons with strata I and II girls. The results indicate a secular trend in the age of menarche when compared with previous Venezuelan studies. Median age for all Carabobo girls is comparable and often slightly lower than recent data from European and American studies.