Hem > Antropologi, Asien, Europa > Indier och européer delar gen för ljus hud

Indier och européer delar gen för ljus hud

november 10, 2013

En ny studie publicerad i PLOS Genetics visar att indier och européer genom härkomst delar allelen SLC24A5 som ger ljus hudfärg.

I Indien förklarar genen 27 procent av hudfärgsvariationerna. Genen finns hos nästan 100 procent av alla européer. Genvarianten ärvdes från en gemensam förfader som levde för mellan 22 000 och 28 000 år sedan.

I Europa finns det ett naturligt urval för genen eftersom ljusare hy behövs för att producera mer D-vitamin i Europa som har mindre solljus. I Indien korrelerar inte genen med breddgrad trots att det lever både mörka och ljusa människor i både norra och södra delen av landet. Genen korrelerar med språk, geografi och demografi.

Omkring 90 procent har denna genvariant i nordvästa Indien. Bland östasiater och afrikaner saknas genvarianten helt. Frekvensen var ungefär 80 procent bland braminer och 10-20 procent bland stamfolken.

Abstrakt

Skin pigmentation is one of the most variable phenotypic traits in humans. A non-synonymous substitution (rs1426654) in the third exon of SLC24A5 accounts for lighter skin in Europeans but not in East Asians. A previous genome-wide association study carried out in a heterogeneous sample of UK immigrants of South Asian descent suggested that this gene also contributes significantly to skin pigmentation variation among South Asians. In the present study, we have quantitatively assessed skin pigmentation for a largely homogeneous cohort of 1228 individuals from the Southern region of the Indian subcontinent. Our data confirm significant association of rs1426654 SNP with skin pigmentation, explaining about 27% of total phenotypic variation in the cohort studied. Our extensive survey of the polymorphism in 1573 individuals from 54 ethnic populations across the Indian subcontinent reveals wide presence of the derived-A allele, although the frequencies vary substantially among populations. We also show that the geospatial pattern of this allele is complex, but most importantly, reflects strong influence of language, geography and demographic history of the populations. Sequencing 11.74 kb of SLC24A5 in 95 individuals worldwide reveals that the rs1426654-A alleles in South Asian and West Eurasian populations are monophyletic and occur on the background of a common haplotype that is characterized by low genetic diversity. We date the coalescence of the light skin associated allele at 22–28 KYA. Both our sequence and genome-wide genotype data confirm that this gene has been a target for positive selection among Europeans. However, the latter also shows additional evidence of selection in populations of the Middle East, Central Asia, Pakistan and North India but not in South India.

PLOS Genetics
LiveScience

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Kategorier:Antropologi, Asien, Europa
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