06-09-2012, 06:46 AM
The A/G ratio for South Asians was 0.820/0.180 in one survey; which included Tamils, Gujaratis, and Telugus. Another study gave the following ratios for Sinhalese and Tamils from Sri Lanka for A/G: 0.50/0.50 and 0.293/0.707 respectively. Finally, the South Asian genome association study has the following ratios for the lightest and darkest quintiles respectively for A/G: 0.90/0.10 and 0.51/0.49. The population was pooled across Punjabis, Gujaratis, Bengalis and Sri Lankans.
The figures for South Asia have me scratching my head a little. It seems pretty clear that SLC24A5 has an association with skin color; it works across Africans and Europeans and it works within South Asians. Nevertheless, why exactly does it exist at such high frequencies as far south as Sri Lanka? And why didnââ¬â¢t it make it to East Asia? Are the South Asian frequencies the result of a selective sweep which started to the north; or is this an endogenous allele which fixed in Europe later? (one would to look at the markers around the South Asian loss of function variant) It does have a northwest to southeast gradient in South Asia, that seems pretty evident.
The figures for South Asia have me scratching my head a little. It seems pretty clear that SLC24A5 has an association with skin color; it works across Africans and Europeans and it works within South Asians. Nevertheless, why exactly does it exist at such high frequencies as far south as Sri Lanka? And why didnââ¬â¢t it make it to East Asia? Are the South Asian frequencies the result of a selective sweep which started to the north; or is this an endogenous allele which fixed in Europe later? (one would to look at the markers around the South Asian loss of function variant) It does have a northwest to southeast gradient in South Asia, that seems pretty evident.