Posted on 05/31/2009 1:23:07 PM PDT by 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.
(Excerpt) Read more at discovermagazine.com ...
“My eyes get greener as I get older. Whats the deal with that.”
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Lighter in color?
If so, you may be losing iris pigment, which can cause your intraocular pressure to become elevated (I’ll skip the exactbphysiologic mechanism for now).
Have you had an eye exam recently?
Me too!!! I had hazel eyes that were more brown than green when I was younger. But now, my eyes are totally green. Crazy!
Every year, all good.
No not lighter greeener. The color looks fake. They were hazel most my life, some people think I wear green contacts now.
I get exams every year too. Last time, the doc said I have very unusual somethings (forget what he called them) in my eyes... they’re tiger striped. He said they are very pretty to look at through the scope, and pretty rare.
“”About 74%” implies that it falls between 73.5 and 74.5%.”
Exactly, and (a) there’s no way they know that, and (b) that degree of precision would be irrelevant to a populist sciencey article anyway.
It’s just kind of crazy/dumb, in a subtle kind of way.
It weird to be sure.
My husbands eyes are sea blue, very nice.
Our daughters eyes almost looked black in color now that she has gotten older they are just dark brown, which really looks cool because she is a blond. She tans so easily she is the California girl.
Hi right back.
Mine are green with a ring of yellow.
I had a girlfriend with solid gray eyes. I loved them, they were so unusual and unique.
That kid needs to lay off the Spice.
Tigroid fundus.
Benign, actually not TOO rare variability in fundus pigmentation. Maybe yours are very pronounced.
I had a heavy red tinge until I hit 30, now at 63 it is a blondish brown with some red high lites, the gods have cursed me it should be a mature Grey.
I bleached my hair when I was younger, to an ash blonde, and when I ran into my long-time best friend, she didn’t know me. I was wearing contacts, and it was at night, and my eyes looked brown.
She said, “I don’t like brown-eyed blondes!” Then I told her who I was. She said, “I STILL don’t like brown-eyed blondes!”
My dad’s eyes were blue, but my mother’s eyes were the very dark brown of native Americans. So I always wonder what’s in the mix that makes the hair red for all of us sibs!!
And there’s nothing wrong with being a California girl!!
“Mature gray?” LOL!
My “mature gray” still looks mighty red in the sun!
The older sibs tell me that their hair went from red to white, though it takes a few years.
I don’t think may hair had any gray until I hit 58. Now it seems to get grayer by the week. *sigh*
Or, “about 74%” would mean something around 74%, with a 1% margin of error so it could be anywhere between 73% and 75%, or depending on how the scientists like to round things, up to a 9% margin of error (if it was a 10% to 50% margin of error, you’d say 70% or 80%, if it’s above 50% you’ve got serious problems).
Also, given that the sample size was 3000 people, that means each person would account for 0.033% of the total, so knowing it to a value of less than 1% (which would be 30 people in this case) is not only possible, but quite feasible.
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* Lincoln, Jackson, Jefferson and Harding are all rumored to be of mixed blood.
I just saw a Mexican man today in San Diego who had the same thing: clearly Mexican features and coloring and wildly blue eyes~! Cool. V’s wife.
That’s interesting. My FIL (very blue eyes) had macular degeneration.
sw
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