Chromosome studies in patients with congenital malformations and mental retardation.

16 (41%) out of 39 individuals referred by physicians because of sexual anomalies showed abnormal karyotypes; the corresponding figure for those investigated due to suspected autosomal aberrations was 37 out of 104 (36%). A special survey was also conducted among 51 mentally defective children with at least 3 malformations; 5 individuals (10%) were observed with chromosome abnormalities plus 3(6%) with rare variants. These results were compared with those presented in 26 other surveys reported in the literature.     

High interpopulation homogeneity in Central Argentina as assessed by Ancestry Informative Markers (AIMs)

The population of Argentina has already been studied with regard to several genetic markers, but much more data are needed for the appropriate definition of its genetic profile. This study aimed at investigating the admixture patterns and genetic structure in Central Argentina, using biparental markers and comparing the results with those previously obtained by us with mitochondrial DNA (mtDNA) in the same samples. A total of 521 healthy unrelated individuals living in 13 villages of the Córdoba and San Luis provinces were tested. The individuals were genotyped for ten autosomal ancestry informative markers (AIMs). Allele frequencies were compared with those of African, European and Native American populations, chosen to represent parental contributions. The AIM estimates indicated a greater influence of the Native American ancestry as compared to previous studies in the same or other Argentinean regions, but smaller than that observed with the mtDNA tests. These differences can be explained, respectively, by different genetic contributions between rural and urban areas, and asymmetric gene flow occurred in the past. But a most unexpected finding was the marked interpopulation genetic homogeneity found in villages located in diverse geographic environments across a wide territory, suggesting considerable gene flow.     

Brief communication: Population data support the adaptive nature of HACNS1 sapiens/neandertal‐chimpanzee differences in a limb expression domain

The 546‐base pair enhancer of limb expression HACNS1, which is highly constrained in all terrestrial vertebrates, has accumulated 16 human‐specific changes after the human‐chimpanzee split. There has been discussion whether this process was driven by positive selection or biased gene conversion, without considering population data. We studied 83 South Amerindian, 11 Eskimo, 35 Europeans, 37 Bantu, and non‐Bantu Sub‐Saharan speakers, and 28 Brazilian mestizo samples and found no variation in this DNA region. Similar lack of variability in this region was found in four Africans, five Europeans or Euro‐derived, two Asians, one Paleo‐Eskimo, and one Neandertal sequence, whose whole genomes are publicly available. No difference was found. This result favors the interpretation of past positive and present conservative selection, as would expected in a region which influences Homo‐specific traits as important as opposable thumbs, manual dexterity, and bipedal walking. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Beta-globin gene cluster haplotype distribution in five Brazilian Indian tribes

Haplotypes derived from five polymorphic restriction sites in the beta-globin gene cluster were investigated in 139 individuals from five different Brazilian Indian tribes by the polymerase chain reaction (PCR). Eight haplotypes were identified. Haplotypes 2 (+????) and 6 (?++?+) were the most frequent and were common to all tribes. Their prevalences ranged from 60% to 93% and from 3% to 18%, respectively. Average heterozy-gosity measured by the Gini-Simpson index is markedly reduced among these Brazilian Indians when compared with Europeans (56%), but much less (8%) in relation to Asiatics, suggesting the absence of an important bottleneck effect in the early colonization of South America. The coefficient of gene differentiation (GST′) was estimated as 0.082 among six Brazilian Indian tribes, but when only three Tupi-Mondé-speaking tribes were considered, this estimate was reduced to 0.030. © 1995 Wiley-Liss, Inc.