Estudo de ancestralidade através de marcadores genéticos uniparentais

Abstract

The arrival of the first inhabitants approximately 15.000 years ago and Portuguese settlers and Africans slaves since the 15th century in successive migrations in South America, lead to the formation of a mixed population with considerable diverse background. It is remarkable that population heterogeneity derives from this migrations and from the indigenous amalgamation process after contacts between different ethnic groups, started with America´s colonization by Europeans. Despite of the high genetic heterogeneity, populations that majority keep the genetic identity from their most remote ancestors can still be found in Brazil. The purpose of this research was characterizing the ancestry of the population of Santa Isabel do Rio Negro, Amazonas, with strong Amerindian phenotypic features, and of the indigenous tribe Terena, from Mato Grosso do Sul. We studied paternal uniparental markers linked to no-recombinant region of Y chromosome and maternal markers present in the control region of mitochondrial DNA (mtDNA). Thirty one individuals from Santa Isabel do Rio Negro were genotyped for paternal inheritance. Genotype information of paternal markers from the Terena tribe was already available from a previously study. MtDNA markers were studied in 76 individuals from Santa Isabel do Rio Negro, both male and female, and in 51 male individuals from Terena tribe. Analysis of Y-SNPs markers allowed characterization of Q1a3a* haplogroup, typical of Amerindian, in 55% of Y chromosomes from individuals of Santa Isabel do Rio Negro . By mtDNA markers this study established that haplogroup A is the most common in both populations, occuring in 34% of individuals from Santa Isabel do Rio Negro and 42% of individuals from the Terena tribe. This observation suggests that regarding maternal ancestry, there is no occurrence of significant genetic differentiation among the two populations. On the other hand, Y chromosome analysis revealed occurrence of significant genetic distance between this populations, which can be a result of the difference among populations sample sizes, or can reflect differences between Amerindian s migratory routes previously to colonization. The result also shows that autoctones mitochondrial genomes were better preserved, and new Y chromosome haplogroups were introduced recently in Amerindian population. Therefore, it is, possible to conclude that Santa Isabel do Rio Negro population and Terena indigenous tribe show significant degree of Amerindian ancestry conservation, despite of the long historic contact with European and African, the others people formers the Brazilian population.