Monday, November 05, 2007

OCA2 and eye color

OCA2 and other genes have previously been implicated in eye color (here, here, and a new paper that I haven't blogged on yet) Here, they look at more variants in OCA2 and are able to predict eye color from a "modest number of SNPs in the gene."

Multilocus OCA2 genotypes specify human iris colors

Tony Frudakis, Timothy Terravainen and Matthew Thomas

Human Genetics Volume 122, Numbers 3-4 / November, 2007
Human iris color is a quantitative, multifactorial phenotype that exhibits quasi-Mendelian inheritance. Recent studies have shown that OCA2 polymorphism underlies most of the natural variability in human iris pigmentation but to date, only a few associated polymorphisms in this gene have been described. Herein, we describe an iris color score (C) for quantifying iris melanin content in-silico and undertake a more detailed survey of the OCA2 locus (n = 271 SNPs). In 1,317 subjects, we confirmed six previously described associations and identified another 27 strongly associated with C that were not explained by continental population stratification (OR 1.5–17.9, P = 0.03 to less than 0.001). Haplotype analysis with respect to these 33 SNPs revealed six haplotype blocks and 11 hap-tags within these blocks. To identify genetic features for best-predicting iris color, we selected sets of SNPs by parsing P values among possible combinations and identified four discontinuous and non-overlapping sets across the LD blocks (p-Selected SNP sets). In a second, partially overlapping sample of 1,072, samples with matching diplotypes comprised of these p-Selected OCA2 SNPs exhibited a rate of C concordance of 96.3% (n = 82), which was significantly greater than that obtained from randomly selected samples (62.6%, n = 246, P less than 0.0001). In contrast, the rate of C concordance using diplotypes comprised of the 11 identified hap-tags was only 83.7%, and that obtained using diplotypes comprised of all 33 SNPs organized as contiguous sets along the locus (defined by the LD block structure) was only 93.3%. These results confirm that OCA2 is the major human iris color gene and suggest that using an empirical database-driven system, genotypes from a modest number of SNPs within this gene can be used to accurately predict iris melanin content from DNA.


Lily Bateman said...

how do you get the eye colour you have? does it depend on which parent you are more like? i dont really understad...

Yann Klimentidis said...


You get the eye color you have because of the specific combination of eye color "genes" that you inherit from your ancestors (parents, grandparents etc...). This implies that if your parents had a certain eye color, then you will also probably have that same eye color. However, since eye color can be controlled by more than one gene, it could be that you get a unique combination of eye color "genes" from your parents which results in an eye color that is different than your parents or grandparents.

lili said...

this is just beautiful, it is like jewels, unique and magnificent, i wish i had a beautiful color but i have black olives!

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