Feb
08
2008

Blue’s clues: Geneticists trace roots of blue-eyed traits

Blue for you: Danish researchers have concluded that the genetic trait that leads to blue eyes comes from the mutation of one gene some 6,000 to 10,000 years ago.
Blue for you: Danish researchers have concluded that the genetic trait that leads to blue eyes comes from the mutation of one gene some 6,000 to 10,000 years ago.Courtesy wikipedia
Do you have blue eyes? If yes, you’re genetically connected to Paul Newman, Brad Pitt and Gwyneth Paltrow according to the findings of a new study.

Researchers in Denmark have announced their finding that all people with blue eyes have a single, common ancestor. Their theory is that a genetic mutation occurred 6,000 to 10,000 years ago that was the beginning of the blue-eyed phenomenon.

Through their study, all humans at first had brown eyes. A mutation created an on/off switch in a specific gene controlling eye color of humans. When triggered to switch off, it stopped the body’s ability to make brown eyes, researchers say. More scientifically, the off switch reduces the body’s ability to create melanin in the iris of the eye. With less melanin, brown eye coloring is diluted to blue.

It’s a very specific mix of genetic code that leads to blue eyes, the researchers continue, while there is much diversity in the genetic make-up of brown- or green-eyed individuals.

The best way to think of it, the researchers add, is that our genetic make-up is like a deck of shuffling cards. The traits from our genes recombine in various forms to impact things like hair color, baldness, freckles and beauty spots. Those changes don’t have a huge impact on the survival of their carriers.

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Your Comments, Thoughts, Questions, Ideas

Liza's picture
Liza says:

OK, I read this article. In the news, I mean. And I hoped someone would post it here, because I'm confused.

My mother has green eyes. My father's are blue.
Two of my siblings have blue eyes. My other brother and I have green eyes.

My husband and I both have green eyes.
Our older daughter's eyes are green, but our youngest has blue.

Everyone's done those super-simplified Punnett Squares where you figure the probability of traits for offspring of a parent with blue eyes and a parent with brown eyes. But those are too simple to tell you anything about people with green eyes. And, darn it, isn't it all about me? :)

posted on Fri, 02/08/2008 - 5:42pm
bryan kennedy's picture

The Tech Museum has a good answer to your question from a geneticist. One of their visitors wrote in with a similar question to yours and the answer describes how people actually end up with brown, blue, or even green eyes. As with many things it is more complex than the simple explanation we normally hear. Put simply, eye color isn't linked to one single genetic trait.

posted on Mon, 02/11/2008 - 12:10pm
Anonymous's picture
Anonymous says:

If you have green eyes, it is just a variation of brown eyes but less melanin (mentioned in another article that announced this finding that was the basis of the reader's background information to understand the differences). Unlike blue eyes which is almost absolutely an entire lack of melanin (this is debatable everyone has their own opinions about that). Brown eyes have the most melanin, green have less of the brown melanin but still quite a bit, and blue has (again) none at all (there is usually traces of some however which I think contributes to the different shades of blue; I could be wrong). The Punnet Squares are only for probability. In the eyes case, it determines the probability of how much melanin a child's eyes may have based on the "shuffling" (as mentioned in the article) of the genes that the parents contribute from their parents and so forth. It isn't supposed to be exact only an idea of what to look for. ^_^; I hope that helps

posted on Sun, 05/24/2009 - 6:21am
twila_08's picture
twila_08 says:

That's kind of scary to think that you can be related to someone that you don't even know. But in a way I feel like it's a cool thing. My eyes are not blue but I kind of feel like this pretains to every color eyes.

Twila Turnage

posted on Wed, 02/13/2008 - 7:34pm
Jenna Renald's picture

ok..i have a question for biology. We have this question "if you could choose 5 traites you would want your offspring to have, what would they be and explain why for each. i said i want them to have blue eyes..but i dont know why. HELP!

posted on Tue, 03/11/2008 - 6:18pm
trueblue's picture
trueblue says:

I was just wondering if anyone know's if it has been a proven fact that people with blue eyes or with a very low melitonin count in there eyes have better vision than those with a high level of melitonin in there eyes, or if there is "any" difference in there vision?

posted on Sat, 01/16/2010 - 3:21am
Crist's picture
Crist says:

@trublue

Melatonin is a hormone that performs several functions including but not limited to the synchronization of the sleep cycle in humans.

Melanin is the word you're looking for I'd wager. Cheers.

posted on Tue, 07/02/2013 - 1:33pm
Greg7's picture
Greg7 says:

How does the brain control heart rate?

posted on Fri, 07/05/2013 - 2:28pm

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