Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Brazil.
PLoS One. 2012;7(7):e40007. doi: 10.1371/journal.pone.0040007. Epub 2012 Jul 10.
In a large variety of genetic studies, probabilistic inferences are made based on information available in population databases. The accuracy of the estimates based on population samples are highly dependent on the number of chromosomes being analyzed as well as the correct representation of the reference population. For frequency calculations the size of a database is especially critical for haploid markers, and for countries with complex admixture histories it is important to assess possible substructure effects that can influence the coverage of the database. Aiming to establish a representative Brazilian population database for haplotypes based on 23 Y chromosome STRs, more than 2,500 Y chromosomes belonging to Brazilian, European and African populations were analyzed. No matter the differences in the colonization history of the five geopolitical regions that currently exist in Brazil, for the Y chromosome haplotypes of the 23 studied Y-STRs, a lack of genetic heterogeneity was found, together with a predominance of European male lineages in all regions of the country. Therefore, if we do not consider the diverse Native American or Afro-descendent isolates, which are spread through the country, a single Y chromosome haplotype frequency database will adequately represent the urban populations in Brazil. In comparison to the most commonly studied group of 17 Y-STRs, the 23 markers included in this work allowed a high discrimination capacity between haplotypes from non-related individuals within a population and also increased the capacity to discriminate between paternal relatives. Nevertheless, the expected haplotype mutation rate is still not enough to distinguish the Y chromosome profiles of paternally related individuals. Indeed, even for rapidly mutating Y-STRs, a very large number of markers will be necessary to differentiate male lineages from paternal relatives.
在大量的遗传研究中，基于群体数据库中的信息进行概率推断。基于群体样本的估计的准确性高度依赖于分析的染色体数量以及参考群体的正确表示。对于频率计算，数据库的大小对于单倍体标记尤其重要，对于具有复杂混合历史的国家，评估可能影响数据库覆盖范围的亚结构效应非常重要。为了基于 23 个 Y 染色体 STR 建立一个具有代表性的巴西人群单倍型数据库，分析了属于巴西、欧洲和非洲人群的 2500 多个 Y 染色体。无论巴西目前存在的五个地缘政治区域的殖民历史有何不同，对于 23 个研究的 Y-STRs 的 Y 染色体单倍型，都没有发现遗传异质性，并且在该国所有地区都以欧洲男性血统为主导。因此，如果我们不考虑分布在全国各地的各种美洲原住民或非裔孤立人群，那么一个单一的 Y 染色体单倍型频率数据库将足以代表巴西的城市人口。与最常研究的 17 个 Y-STR 组相比，这项工作中包含的 23 个标记能够在群体内非相关个体的单倍型之间提供高的区分能力，并且增加了区分父系亲属的能力。然而，预期的单倍型突变率仍然不足以区分父系相关个体的 Y 染色体谱。事实上，即使对于快速突变的 Y-STR，也需要大量的标记来区分男性血统和父系亲属。
