Why Everyone In My Family Has Blue Eyes, Except Me
Today, I discovered “The Spitoon“, the blog from 23andMe, the company dedicated to personal genomics. Really interesting material. I found this article particularly eye-catching:
I’m curious about this, of course, because while I have green eyes, my wife Carolyn & my two sons have blue eyes. It seems that this isn’t even due to a single gene – it’s literally a single nucleotide pair. From the article:
Three recently published papers (here, here, and here) report that a single SNP determines whether a person’s eyes will be blue; every blue-eyed person in the world has the same version. The findings also suggest that the blue-eyed version of the SNP can be traced back to a single ancestor that lived about 6,000 to 10,000 years ago.
It’s been known for a while that eye colors like green and hazel (deviations from the brown color found in the majority of people) can be explained by SNPs in a gene called OCA2. The protein made by this gene is involved in the production of melanin, a pigment found in the cells of the iris. This is the same pigment that gives your hair and skin their color. Darker eyes have more melanin than lighter colored eyes.
But none of the known variations in OCA2 could explain blue eyes. The new research seems to have solved the mystery. A SNP near OCA2, but not in it, determines whether a person will have blue eyes.
The SNP, rs12913832, is actually in a gene called HERC2. Scientists think that instead of affecting HERC2, the SNP controls how much protein will be made from the nearby OCA2 gene. Low levels of OCA2 protein, caused by the G version of the SNP, lead to lower levels of melanin, which in turn leads to blue eyes. 23andMe customers can check their genotype at this SNP in the Genome Explorer or in the Gene Journal (Note: In the Gene Journal you’ll see other SNPs also associated with eye color. The combination of these SNPs with the blue-eyed version of rs12913832 can end up giving a person green eyes instead of blue).
What a great blog. Sign me up for that feed.
As a side note, Michael Arrington has posted his account info from 23andMe on TechCrunch, so you can live vicariously through him in case you are short $1000. I have to admit, seeing those results makes me jealous – I’d love that kind of genetic detail on myself & my family members.