RESUMO
We analyzed the European genetic contribution to 10 populations of African descent in the United States (Maywood, Illinois; Detroit; New York; Philadelphia; Pittsburgh; Baltimore; Charleston, South Carolina; New Orleans; and Houston) and in Jamaica, using nine autosomal DNA markers. These markers either are population-specific or show frequency differences >45% between the parental populations and are thus especially informative for admixture. European genetic ancestry ranged from 6.8% (Jamaica) to 22.5% (New Orleans). The unique utility of these markers is reflected in the low variance associated with these admixture estimates (SEM 1.3%-2.7%). We also estimated the male and female European contribution to African Americans, on the basis of informative mtDNA (haplogroups H and L) and Y Alu polymorphic markers. Results indicate a sex-biased gene flow from Europeans, the male contribution being substantially greater than the female contribution. mtDNA haplogroups analysis shows no evidence of a significant maternal Amerindian contribution to any of the 10 populations. We detected significant nonrandom association between two markers located 22 cM apart (FY-null and AT3), most likely due to admixture linkage disequilibrium created in the interbreeding of the two parental populations. The strength of this association and the substantial genetic distance between FY and AT3 emphasize the importance of admixed populations as a useful resource for mapping traits with different prevalence in two parental populations.
Assuntos
Alelos , População Negra/genética , Genética Populacional , África/etnologia , Negro ou Afro-Americano , Elementos Alu/genética , População Negra/classificação , DNA Mitocondrial/genética , Europa (Continente)/etnologia , Feminino , Frequência do Gene , Pool Gênico , Marcadores Genéticos , Haplótipos/genética , Humanos , Jamaica , Desequilíbrio de Ligação , Masculino , Polimorfismo Genético , Razão de Masculinidade , Estados Unidos , Cromossomo Y/genéticaRESUMO
We analyzed the European genetic contribution to 10 populations of Africans descent in the United States (Maywood, Illinois; Detroit; New York; Philadelphia; Pittsburgh; Baltimore; Charleston, South Carolina; New Orleans; and Houston) and in Jamaica, using nine autosomal DNA markers. These markers either are population-specific or show frequency differences >45 percent between the parental populations and are thus especially informative for admixture. European genetic ancestry ranged from 6.8 percent (Jamaica) to 22.5 percent (New Orleans). The unique utility of these markers is reflected in the low variance associated with these admixture estimates (SEM 1.3 percent -2.7 percent). We also estimated the male and female European contribution to African Americans. on the basis of informative mtDNA (haplogroups H and L) and Y Alu polymorphic markers. Results indicate a sex-biased gene flow from Europeans, the male contribution being substantially greater that the female contribution. mtDNA haplogroups analysis shows no evidence of a significant maternal Amerindian contribution to any of the 10 populations. We detected significant nonrandom association between two markers located 22 cM apart (FY-null and AT3), most likely due to admixture linkage disequilibrium created in the interbreeding of the two parental populations. The strength of this association and the substantial genetic distance between FY and AT3 emphasize the importance of admixed populations as a useful resources for mapping traits with different prevalence in two parental populations (AU)
Assuntos
Feminino , Humanos , Masculino , Alelos , Genética Populacional , /genética , África/etnologia , Elementos Alu/genética , Negro ou Afro-Americano , DNA Mitocondrial/genética , Europa (Continente)/etnologia , Frequência do Gene , Pool Gênico , Marcadores Genéticos , Haplótipos/genética , Jamaica , Desequilíbrio de Ligação , /classificação , Polimorfismo Genético , Razão de Masculinidade , Estados Unidos , Cromossomo Y/genéticaRESUMO
The haplotypes of the alpha-globin gene cluster were determined for 99 Indians from the Brazilian Amazon region who belong to 5 tribes: Wayampí, Wayana-Apalaí, Kayapó, Arára, and Yanomámi. Three predominant haplotypes were identified: Ia (present in 38.9% of chromosomes), IIIa (25.8%), and IIe (22.1%). The only alpha-globin gene rearrangement detected was alpha alpha alpha 3.7 I gene triplication associated with haplotype IIIa, found in high frequencies (5.6% and 10.6%) in two tribes and absent in the others. alpha-Globin gene deletions that cause alpha-thalassemia were not seen, supporting the argument that malaria was absent in these populations until recently. The heterogeneous distribution of alpha-globin gene haplotypes and rearrangements among the different tribes differs markedly from the homogeneous distribution of beta-globin gene cluster haplotypes and reflects the action of various genetic mechanisms (genetic drift, founder effect, consanguinity) on small isolated population groups with a complicated history of divergence-fusion events. The alpha-globin gene haplotype distribution has some similarities to distributions observed in Southeast Asian and Pacific Island populations, indicating that these populations have considerable genetic affinities. However, the absence of several features of the alpha-globin gene cluster that are consistently present among the Pacific Islanders suggests that the similarity of haplotypes between Brazilian Indians and people from Polynesia, Micronesia, and Melanesia is more likely to result of ancient common ancestry rather than the consequence of recent direct genetic contribution through immigration.