Estructura genética de la población de guatemana. Aplicaciones en el campo antropológico y forense

Resumen

The development of the new techniques of Molecular Biology has been made possible to study different regions within the DNA (autosomic or sexual chromosome, and mitochondrial DNA) and with the Statistic Analysis for this data to obtain all the information for these markers. Some are distinctive markers useful to distinguish between individuals, polymorphic regions and their inheritance. DNA polymorphism and single mutations make a profoundly genetic characterization of a population. We focused on a population from Guatemala. Guatemala is one of the largest countries in Central America (with Nicaragua and Honduras) and its total population is approximately 13 millions individuals, the most populated country in Central America. In Guatemala, different population groups whose structure expresses that they are isolated because of the influence of geographic, linguistic and cultural factors can be found. The objective of this study was to define the genetic structure within the Guatemalan population, Mestizo and Mayan groups. Moreover, we study the Mestizos group representing 60% of the total of the Guatemala population in the present day. Admixture among Amerindians and Spanish currently constitutes the gene pool of Guatemalan Mestizos; so we study the contribution of Mayas and Spanish samples to the Mestizo gene pool. We analyze the genetic data of 15 autosomal short tandem repeat (STR) polymorphisms in 400 unrelated donors living in Guatemala, 200 Mestizos, 200 representing four Mayan population samples and 200 from unrelated donors from Spain. But also, we studied the genetic structure of five Guatemalan populations and the Spanish population using Y chromosome microsatellite markers. We analyzed 17 STRs polymorphisms from the Y Chromosome in 397 unrelated donors representing a total of six population samples from Guatemala and Spain. And also, the characterization of the mtDNA control region from Mestizo population and four aboriginal Guatemalan populations were done; using samples of 191 mayan and 105 Mestizos living in Guatemala. And compared with 295 unrelated Spanish samples. Haplotype frequencies were calculated by gene counting method. Haplotype diversities were calculated according to Nei using Arlequin software. An analysis of molecular variance was also performed. To make the genetic characterization of this country we also included genetics data of other European, Asiatic, Oceanian, African and especially with American countries to compare with our populations studied. Genetic distance, multidimensional scaling and corresponding analysis have been performed in most of the analysis. The estimation of individual ancestry proportions was studied with STRUCTURE. In addition, the relationship between the samples was inferred by Networks. The most relevant results were, Every single a-STR and Y-STR haplotype has been found as unique, among the individuals from Guatemala, there are 205 unique mitochondrial haplotypes. Power of Discrimination in Identifiler Kit is a very powerful tool for genetic identification both in the Mestizo Guatemalan and Spanish populations, but also in the Mayan populations. Furthermore, although the differences between the discrimination power of the Y-STRs markers were explained in the three populations, all the studied markers offer a high discrimination power. The most common Y-STR haplogroup in the Guatemalan Mayan populations is the Q haplogroup. Q haplogroup is the most representative haplogroup in the Mestizo population but R1b1 haplogruop is significant. In the Spanish population, the most common haplogroup is R1b1. Most of the mitochondrial haplogroups in Mayan and Mestizo populations of Guatemala are A and B haplogroups, while in Spanish population the most prevalent is H haplogroup. The appearance of the European and Native American genetic flows in the Mestizo population will be considered as far as the emergence of new haplogroups in the population structure. The Guatemalan population is divided in two subpopulations, one with Mayan origins (isolated and particular), and some others known as Mestizo, which are the result of the mixture between Mayan and Spanish people. An asymmetric flow of the genetic contribution of Mayan and Spanish populations to the Mestizo population is shown. The influence has been higher in Y chromosome and lesser in DNAmt than in the rest of the genome because the source of variability was mainly male of the high proportion of male Spanish colonizers. In the Mestizo population, there are some individuals that have a high percentage of native population instead of other individuals that present a low proportion of those and high of the immigrant population. He also noted that any analysis performed show us the appearance of an African genetic component in the Mestizo population. Characteristic phenomena of endogamous populations are noticed in these aboriginal groups as decrease of variability, PD and heterozygosity due to the limited genetic pool. Studies performed in the Guatemalan population confirm that the rise of homozygosity and the fall of PD in autosomal chromosomes are not linked to a limited number of DNAmt haplotypes and Y chromosome. The limited inheritance of the markers does not strengthen the effects of endogamy. A Native American population with a high variability is a source of microevolution phenomena: gain of mutations, selection, genetic flows and genetic drift. Native American populations can be defined as a model to study all the microevolution phenomena.