Santos Alonso Alegre, Neskuts Izagirre Arribalzaga, Iker Garcia Jimenez, Concepción de la Rúa Vaca
Univ. of the Basque Country, Dept. Genetics, Physical Anthropology and Animal Physiology, Faculty of Science and Technology, Barrio Sarriena s/n 48940 Leioa (Bizkaia)
The apportionment of human diversity in skin colour is atypical. Thus, variation in skin reflectance among populations of the major geographical regions represents an 88% of the global diversity. Despite the intuitive adaptive nature of skin pigmentation, evidence supporting it has been indirect and thus, there are a number of hypotheses on the mechanisms that endow pigmentation with an adaptive value. One would expect to see a signature of positive selection on the sequence diversity and divergence patterns of those genes that played a role in the putative adaptive properties of pigmentation. These genes would point to particular biological pathways which could help us cast some light on the evolutionary meaning of pigmentation. Thus, herein, we apply the phylogenetic approach to detect positive selection in coding sequences by looking at the ratio dN/dS to a battery of over 70 loci in which mutations can affect pigmentation, using trios of mouse, chimp and human orthologues. We also test the Fst values of SNPs of these loci among the three major human groups using as reference the SNP frequency data available online. The amount of SNPs with Fst values greater than background level (considering population history) is significantly greater in the set of loci showing some evidence of positive selection by the phylogenetic approach. However, negatively selected loci also showed some SNPs with significant Fst values. The set of selected SNPs was able to identify 3 different population groups by means of structure.
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