Eye Color Explained: Everything you know is wrong

Discover Magazine ^ | March 13, 2007 | Boonsri Dickinson

[SunkenCiv]

What most people know about the inheritance of eye color is that brown comes from a dominant gene (needing one copy only) and blue from a recessive gene (needing two copies). University of Queensland geneticist Rick Sturm suggests that the genetics are not so clear. "There is no single gene for eye color," he says, "but the biggest effect is the OCA2 gene." This gene, which controls the amount of melanin pigment produced, accounts for about 74 percent of the total variation in people's eye color.

Sturm has recently shown that the OCA2 gene itself is influenced by other genetic components. After gene-typing about 3,000 people, Sturm found that how OCA2 is expressed -- and how much pigment a person has -- is strongly linked to three single nucleotide polymorphisms (SNPs), or single letter variations, in a DNA sequence near the OCA2 gene. That suggests a more complicated story than the blue-recessive/brown-dominant model of eye color. "For example, among individuals carrying the SNP sequence "TGT" at all three locations on both copies of the gene, 62 percent were blue-eyed," says Sturm's colleague David Duffy. By contrast, only 21 percent of individuals carrying only one TGT copy at each location and 7.5 percent of those lacking the TGT entirely had blue eyes.

Depending on the particular combination of SNPs inherited, a person can have a range of OCA2 activity that lands them on the spectrum between blue and brown eyes. What about green eyes? "Green eyes probably represent the interaction of multiple variants within the OCA2 and in other genes, including perhaps the red-hair gene," Duffy says.

[SunkenCiv]

A sampling of the enormous variation in human eye color

[SunkenCiv]

· join list or digest · view topics · view or post blog · bookmark · post a topic ·
	Gods Graves Glyphs	The article is from March 2007, but apparently it didn't get posted. To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach
·Dogpile · Archaeologica · ArchaeoBlog · Archaeology · Biblical Archaeology Society · · Discover · Nat Geographic · Texas AM Anthro News · Yahoo Anthro & Archaeo · Google · · The Archaeology Channel · Excerpt, or Link only? · cgk's list of ping lists ·

[Perdogg]

what about heterochromia?

[chuck_the_tv_out]

"accounts for about 74 percent of the total variation"

About 74%! Reminds me of when Darwin wrote that the Wealden deposits were 306,662,400 years old. (On the origin of species by means of natural selection or the preservation of favored races in the struggle for life, 1st edition)

It's either 74%, or it's not 74%. It might be "about 75%", but "about 74%" is pure tardedness.

[EyeGuy]

Yes as the article staes, most people are not aware of the fact that iris pigmentation is based completely on the AMOUNT of iris pigment, not its inherent coloration.

Swedes for example simply have less iris pigment for example than Africans.

The presence of pigment throughout the eye, does have some beneficial, protective effects for other ocular pathology, such as age-related macular degneration (ARMD).

[ElayneJ]

for later

[Larry Lucido]

What are you, some kind of homochrome?

[Monkey Face]

..."Green eyes probably represent the interaction of multiple variants within the OCA2 and in other genes, including perhaps the red-hair gene," Duffy says.

Hah! It's my red hair, my dad's blue eyes, and my mom's brown eyes.

Green eyes and red hair...how come only us wimmins have that? I've never seen a guy with red hair and green eyes....

:oþ

[Perdogg]

yep, just like 99% of us.

[MyTwoCopperCoins]

Both parents of this kid are black, BTW.

[raybbr]

It's either 74%, or it's not 74%. It might be "about 75%", but "about 74%" is pure tardedness.

This post is pure childishness.

[Little Bill]

Me.

[To Hell With Poverty]

Wow! Striking. What a beautiful little boy!

[srmorton]

Eye color is an example of what biologists call “continuous variation” - a trait that is obviously influenced by multiple genes. I always remind my students that this is the case even while I am using eye color as an example of a simple Mendelian trait. It is easy for them to relate to since most people have eyes that are some shade of brown or blue.

[Pharmboy]

Mine are hazel, as in the lower left in your photograph. What was particularly interesting to me was that for the first 45 years of my life my eyes were light brown with a few green flecks. After 45, they turned hazel...I even changed the eye color answer on my driver's license. My dad had light blue eyes, my mom brown, and my sister has blue.

And our genes are quite mixed up: Celtic, Romanian, Jewish and Ukrainian.

[svcw]

My eyes get greener as I get older. What’s the deal with that.
My grandson eyes were blue blue blue until he turned fourish and changed to dark brown - freaky really.

[Monkey Face]

Prove it! Show me a photo!! LOL!
Congratulations!!

You rock!
I have six red-haired siblings but they ALL have brown eyes. My hair is the darkest (dark auburn) and my eyes the lightest (hazel green.)

My son’s eyes are “honey” colored.

[fieldmarshaldj]

Is Vanessa Williams his mom ?

[Ole Okie]

It might be "about 75%", but "about 74%" is pure tardedness.

Details, details.

You're right. "About 74%" implies that it falls between 73.5 and 74.5%.

"About 75% would (to me) imply that the value is somewhere between 70 and 80%.

Or, using the law of the WAG, 75% would imply a value somewhere between 50 and 100%.

[Monkey Face]

Hi!

Haven’t seen you for a while!
All my sibs had blue-eyed first-born children except me. My son’s were “honey eyes.” However, after the first child, the eyes could vary, though never seeming to get out of being “blue” or “brown.”

Strange stuff, that.