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Genes and skin color

Tecnociencia cor da pele NOVADaniel BuenoAlterations in different segments of one or more genes may influence the skin pigmentation of populations having a high degree of miscegenation, according to a study coordinated by geneticist Maria Cátira Bortolini from the Genetics Department at the Federal University of Rio Grande do Sul (UFRGS). In the study, biologist Caio Cerqueira analyzed 18 genetic alterations, known as single nucleotide polymorphisms (SNPs), distributed across nine genes associated with pigmentation of the skin, eyes, and hair.  SNPs are genetic alterations in which only one of the “letters” of a DNA sequence (A, T, C, or G) is swapped out for another.  It has been known for some time that these 18 alterations are directly or indirectly linked to human pigmentation. In their work, Cerqueira and colleagues searched for potential associations between these SNPs and levels of melanin, the pigment that gives skin its color, in 352 people from the state of Rio Grande do Sul and 148 from the state of Bahia (PLOS One, May 2014). These states were selected because of the contrast in the components of their miscegenation; in Bahia, far more Africans and native South Americans mixed with Europeans than in Rio Grande do Sul, where descendants of immigrants from many European countries predominate. Four of the alterations were found to be good predictors of the degree of skin pigmentation in these mixed-race populations. But only two of them were directly linked with melanin levels in the participants from both Brazilian states. According to Bortolini, these alterations could be very valuable to forensic scientists because they were linked to pigmentation levels in both groups, regardless of degree of miscegenation. “Using this type of information and a DNA sample found at the scene of a crime, the police might obtain a more detailed portrait of the suspect based on these two genetic alterations that are related to skin color,” the geneticist explains.