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Scientists research cause of blue eyes


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Genetic mutation makes those brown eyes blue

Scientists find that blue-eyed individuals have a single, common ancestor

by Jeanna Bryner

updated 12:01 p.m. MT, Thurs., Jan. 31, 2008People with blue eyes have a single, common ancestor, according to new research.

A team of scientists has tracked down a genetic mutation that leads to blue eyes. The mutation occurred between 6,000 and 10,000 years ago, so before then, there were no blue eyes.

"Originally, we all had brown eyes," said Hans Eiberg from the Department of Cellular and Molecular Medicine at the University of Copenhagen.

The mutation affected the so-called OCA2 gene, which is involved in the production of melanin, the pigment that gives color to our hair, eyes and skin.

"A genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch,' which literally 'turned off' the ability to produce brown eyes," Eiberg said.

The genetic switch is located in the gene adjacent to OCA2 and rather than completely turning off the gene, the switch limits its action, which reduces the production of melanin in the iris. In effect, the turned-down switch diluted brown eyes to blue.

If the OCA2 gene had been completely shut down, our hair, eyes and skin would be melanin-less, a condition known as albinism.

"It's exactly what I sort of expected to see from what we know about selection around this area," said John Hawks of the University of Wisconsin-Madison, referring to the study results regarding the OCA2 gene. Hawks was not involved in the current study.

Baby blues

Eiberg and his team examined DNA from mitochondria, the cells' energy-making structures, of blue-eyed individuals in countries including Jordan, Denmark and Turkey. This genetic material comes from females, so it can trace maternal lineages.

They specifically looked at sequences of DNA on the OCA2 gene and the genetic mutation associated with turning down melanin production.

Over the course of several generations, segments of ancestral DNA get shuffled so that individuals have varying sequences. Some of these segments, however, that haven't been reshuffled are called haplotypes. If a group of individuals shares long haplotypes, that means the sequence arose relatively recently in our human ancestors. The DNA sequence didn't have enough time to get mixed up.

"What they were able to show is that the people who have blue eyes in Denmark, as far as Jordan, these people all have this same haplotype, they all have exactly the same gene changes that are all linked to this one mutation that makes eyes blue," Hawks said in a telephone interview.

Melanin switch

The mutation is what regulates the OCA2 switch for melanin production. And depending on the amount of melanin in the iris, a person can end up with eye color ranging from brown to green. Brown-eyed individuals have considerable individual variation in the area of their DNA that controls melanin production. But they found that blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes.

"Out of 800 persons we have only found one person which didn't fit — but his eye color was blue with a single brown spot," Eiberg told LiveScience, referring to the finding that blue-eyed individuals all had the same sequence of DNA linked with melanin production.

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So you say, so you say. Don't you know blue eyes send out stronger energy beams? Superman's eyes are blue.

And have you noted that there are only two blue-eyed smilies?

:computertrash: :'(

I think those blue-ies are trying to tell us something... :blink:

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so, blue eyes are a result of evolution then, no kidding, well there's a surprise <_<

:beer: and now that we blueys (is that a word ?) have been outed as mutants, we have a genuine reason to go on the rampage, conquering the world and exploiting it's resources .........

......... oh sorry, we've been there done that already :shifty:

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so, blue eyes are a result of evolution then, no kidding, well there's a surprise <_<

:beer: and now that we blueys (is that a word ?) have been outed as mutants, we have a genuine reason to go on the rampage, conquering the world and exploiting it's resources .........

......... oh sorry, we've been there done that already :shifty:

:thumbsup:

I am a proud member of the melanin-impoverished mutant albino genetic-recessive global minority!

I have a theory that since blue eyes and light skin is only a recent development in the evolution of human beings. Then it must follow that we are also an improvement over earlier models.

:yay:

:P

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My eyes are hazel, green with a smattering of brown, we have a high amount of grey eyes in my family, my daughter inherited them as well. Lot's of folks with jet black hair, pale skin and grey eyes in my clan...my sister is the oddball with brown eyes, she always felt like she was jipped !

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My favorite physical part of a woman is the eyes, ................

Suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuure........ :lol:

My wife will still dispute this;but the first night I ever met her;the very first thing I noticed about her was her beautiful green eyes.-I still could look into them forever. :wub:

Now;as far as the second thing I noticed,or should I say "things", I ain't sayin'..... :whistling:

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Suuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuure........ :lol:

My wife will still dispute this;but the first night I ever met her;the very first thing I noticed about her was her beautiful green eyes.-I still could look into them forever. :wub:

Now;as far as the second thing I noticed,or should I say "things", I ain't sayin'..... :whistling:

I'm not saying I don't notice other things. :D But eyes make my stomach flip. All the beauty of the sunset or the ocean condensed into one set of peepers- Pretty eyes can enslave me. Copious back rubs, midnight trips to the store, the whole enchilada.

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