Analysis of paternal lineages in Brazilian and African populations

The present-day Brazilian population is a consequence of the admixture of various peoples of very different origins, namely, Amerindians, Europeans and Africans. The proportion of each genetic contribution is known to be very heterogeneous throughout the country. The aim of the present study was to compare the male lineages present in two distinct Brazilian populations, as well as to evaluate the African contribution to their male genetic substrate. Thus, two Brazilian population samples from Manaus (State of Amazon) and Ribeirão Preto (State of São Paulo) and three African samples from Guinea Bissau, Angola and Mozambique were typed for a set of nine Y chromosome specific STRs. The data were compared with those from African, Amerindian and European populations. By using Y-STR haplotype information, low genetic distances were found between the Manaus and Ribeirão Preto populations, as well as between these and others from Iberia. Likewise, no significant distances were observed between any of the African samples from Angola, Mozambique and Guinea Bissau. Highly significant Rst values were found between both Brazilian samples and all the African and Amerindian populations. The absence of a significant Sub-Saharan African male component resulting from the slave trade, and the low frequency in Amerindian ancestry Y-lineages in the Manaus and Ribeirão Preto population samples are in accordance with the accentuated gender asymmetry in admixture processes that has been systematically reported in colonial South American populations.

Análisis de la estructura genética en una muestra poblacional de Bucaramanga, departamento de Santander / An assessment of genetic structure in a Bucaramanga, department of Santander, population sample

Introducción: El fenómeno de sub-estructura en las poblaciones ha tenido desde hace varios años un abordaje amplio, que se enfocó, entre otros, en la identificación y cuantificación de la mezcla étnica presente en estudios de mapeo asociativo, para comprobar la asociación de marcadores polimórficos en el desarrollo de enfermedades comunes complejas, como responsable de falsos positivos. No obstante el reconocimiento de este problema, no se tiene suficiente información genética en el contexto nacional ni local que permita determinar la posible diferenciación de subgrupos poblacionales en cada región en particular. Objetivo: Determinar la estructura genética en una muestra poblacional de la ciudad de Bucaramanga, a partir del análisis de 19 marcadores microsatélites autosómicos en distintos subgrupos poblacionales. Metodología: De la base de datos del Laboratorio de Genética Humana de la Universidad Industrial de Santander, se seleccionaron aleatoriamente 350 muestras de ADN, y se amplificaron 19 marcadores autosómicos Short Tandem Repeat mediante los "kits Powerplex® 16 y FFFL (Promega)".Resultados: En el análisis de equilibrio Hardy Weinberg, no se obtuvieron diferencias estadísticamente significativas en 18 de 19 marcadores Short Tandem Repeat autosómicos analizados en la población de Bucaramanga. El único marcador que mostró no estar en equilibrio Hardy Weinberg en la población de Bucaramanga fue el F13B (valor de significancia de p=0.00264, después de aplicar la corrección de Bonferroni). Discusión: Las poblaciones representadas en los seis estratos socioeconómicos mostraron alta diversidad genética intragrupos, que ratificó una alta variabilidad entre los individuos de la ciudad de Bucaramanga, acorde con el bajo valor de FST entre distintos grupos, determinado en el análisis molecular de varianza con base en frecuencias alélicas observadas para los 19 Short Tandem Repeat analizados.

Introduction: The phenomenon of substructure in the populations has been greatly analyzed for several years, and it has been focused especially on the identification and quantification of ethnic mixture present in studies of associative mapping to verify the association of polymorphic markers in the development of complex and common diseases responsible for false positives. Nevertheless, despite the recognition of this issue, there is insufficient genetic information within the national or local contexts that allow assessing the possible differentiation of population sub-groups in each particular region. Objective: To determine the genetic structure in the city of Bucaramanga through the analysis of 19 autosomal microsatellite markers in different subgroups of the population. Methodology: A total of 350 DNA samples were randomly selected from the database of the Human Genetic Laboratory at Universidad Industrial de Santander by using Epi Info version 6.04 2001. Also, 19 Short Tandem Repeat markers were amplified using "kits Powerplex® 16 and FFFL (Promega)". Results: In the Hardy Weinberg equilibrium analysis (100 steps in Markov chain and 1000 dememorization steps), no statistically significant differences in 18 out of the 19 analyzed STRs markers in the population of Bucaramanga were obtained. A unique marker that proved not present in HWE in the population of Bucaramanga was the F13B (for a significance value of p=0.00264, after applying the Bonferroni correction). Discussion: The populations represented in the six socioeconomic levels presented high genetic diversity intragroups, which ratified the high variability among the individuals in this city according to the low value of FST for different groups, determined via the molecular analysis of variance based on the allelic frequencies observed for the 19 analyzed Short Tandem Repeats.

Population and mutation analysis of Y-STR loci in a sample from the city of São Paulo (Brazil)

The haplotypes of seven Y-chromosome STR loci (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, and DYS393) were determined in a sample of 634 healthy Brazilian males (190 adult individuals and 222 father-son pairs). The 412 adults were unrelated, and the 222 father-son pairs had their biological relationship confirmed using autosomal STRs (LR > 10,000). Among the 412 adults, a total of 264 different 7-loci haplotypes were identified, 210 of which were unique. The most frequent haplotype was detected in 31 instances, occurring with a frequency of 7.52 percent. The haplotype diversity index was calculated as 98.83 percent. Upon transmission of the 1,554 alleles, in 222 father-son pairs, six mutations were observed, with an average overall rate of 3.86 x 10-3 per locus. A haplotype with a duplicated DYS389I locus, and another with duplicated DYS389I, DYS389II, and DYS439 loci were detected in both fathers and their respective sons.

Variabilidad genética en 17 microsatélites del Cromosoma Y en dos poblaciones nativas de Argentina (Tobas, Collas) / Genetic Variability in 17 Y-STR loci of a native population from Argentine (Tobas, Collas)

Se analizan 17 marcadores microsatélites del cromosoma Y del tipo Short Tandem Repeats (STRs) (DYS19,DYS3891, DYS38911, DYS390, DYS391, DYS392, DYS393, DYS385, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635, y GATA H4)en dos poblaciones nativas de las regiones Norte y Noroeste de la Argentina (Tobas y Collas)