Blue-eyed humans have a single, common ancestor (1/31/2008)
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| Blue eye color phenotype |
New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.
What is the genetic mutation
"Originally, we all had brown eyes", said Professor Eiberg from the Department of Cellular and Molecular Medicine. "But 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". The OCA2 gene codes for the so-called P protein, which is involved in the production of melanin, the pigment that gives colour to our hair, eyes and skin. The "switch", which is located in the gene adjacent to OCA2 does not, however, turn off the gene entirely, but rather limits its action to reducing the production of melanin in the iris - effectively "diluting" brown eyes to blue. The switch's effect on OCA2 is very specific therefore. If the OCA2 gene had been completely destroyed or turned off, human beings would be without melanin in their hair, eyes or skin colour - a condition known as albinism.
Limited genetic variation
Variation in the colour of the eyes from brown to green can all be explained by the amount of melanin in the iris, but blue-eyed individuals only have a small degree of variation in the amount of melanin in their eyes. "From this we can conclude that all blue-eyed individuals are linked to the same ancestor," says Professor Eiberg. "They have all inherited the same switch at exactly the same spot in their DNA." Brown-eyed individuals, by contrast, have considerable individual variation in the area of their DNA that controls melanin production.
Professor Eiberg and his team examined mitochondrial DNA and compared the eye colour of blue-eyed individuals in countries as diverse as Jordan, Denmark and Turkey. His findings are the latest in a decade of genetic research, which began in 1996, when Professor Eiberg first implicated the OCA2 gene as being responsible for eye colour.
Nature shuffles our genes
The mutation of brown eyes to blue represents neither a positive nor a negative mutation. It is one of several mutations such as hair colour, baldness, freckles and beauty spots, which neither increases nor reduces a human's chance of survival. As Professor Eiberg says, "it simply shows that nature is constantly shuffling the human genome, creating a genetic cocktail of human chromosomes and trying out different changes as it does so."
You can view the Full Article Online
Note: This story has been adapted from a news release issued by the University of Copenhagen
Comments:
| 1. |
Ted |
1/31/2008 8:20:24 PM MST |
What can be said for those of us whose eye colour varie's from blue-gray to hazel.
Is it more of a genetic mutation or is the genetic system trying to correct/control the mutation?
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| 2. |
Steve |
1/31/2008 8:25:16 PM MST |
Nope. You're just a freak. |
| 3. |
Mike |
1/31/2008 9:07:17 PM MST |
Ted, I've always wondered about that. Post back here if you find anything on it. |
| 4. |
emma |
2/1/2008 11:47:59 AM MST |
i'm like ted, my eyes are blue on the outside and brown/orange on the middle. but isn't eye color a multiple allele kinda thing? |
| 5. |
lee |
2/1/2008 3:16:58 PM MST |
My eyes are brown, means im a thoroughbred an the rest of u are mungrels |
| 6. |
matt |
2/1/2008 7:03:56 PM MST |
The actual article has a lot more information if you are interested in the other mutations. |
| 7. |
victoria |
2/1/2008 8:36:44 PM MST |
i agree.... my eyes are blue/grey/green and brown closer to the iris.... my eyes change color all the time... what of that? |
| 8. |
Boogey |
2/1/2008 10:28:53 PM MST |
This doesn't seem right. Eye colour is determined by more than one gene, and blue eyes are a recessive trait. That means that even if the "common ancestor" had one gene turned off, other genes would likely make up for it and perhaps they would have a slightly lighter color of brown in their eye. Even if they were blue-eyed, since they were the only blue-eyed individual, their children would all be brown-eyed anyway since blue eyes are a recessive trait... |
| 9. |
nellie jones |
2/5/2008 3:11:50 PM MST |
with Boogey on this , the recessive gene thing - though the OCA2 gene code is compelling, in that it is a start. I have light brown eyes but a friend I have known for some years thought that my eyes were blue. I do have genes for blue eyes! |
| 10. |
danny |
2/6/2008 11:45:04 AM MST |
Everything you think you know about genes is wrong. |
| 11. |
GJ |
2/6/2008 11:54:44 AM MST |
Boogey - when this mutation occurred I don't believe there were societal controls on reproduction and quite likely that interbreeding occurred in isolated populations. So Father/Daughter Brother/Sister Halfbrother/halfsister offspring with this recessive gene could show up as blue eyes at second generation. Even if this interbreeding didn't occur between siblings or parents/offspring, the blue-eyed phenotype would show up, though further away in time from the original mutation.
As to more than one gene causing eye color, I am not an expert but why do you believe this? That would certainly be a killer for this study.
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| 12. |
wook |
2/7/2008 4:01:22 AM MST |
Recessive genes do not exist. Its a conspiracy drummed up by the milkman/mailman's lobby to hide the fact that your kids look more like them than you. Its a known fact that more than 75% of the earths population is fathered by them. Thats the truth cuz I seen it on fox news!! |
| 13. |
Adam |
2/8/2008 2:41:50 PM MST |
Wook, that would explain why my sister and I came out looking decidedly...ethnic, despite our grandparents' insistence that our background is strictly swiss, german, and irish. |
| 14. |
mindboggled |
2/8/2008 6:00:23 PM MST |
WoW! A common ancestor? You don't say. |
| 15. |
chris |
2/12/2008 4:07:44 PM MST |
you get a 1 gene for eye color from each of your parents.
a couple with brown or green eyes CAN have a child with blue eyes IF they both have a recessive blue gene for eyes.
two blue eyed parents can ONLY have a brown eyed child if the mother had an affair or they adopt.
10,000 years ago a small family tribe got busy with each other alot, then got busy with the rest of the world....alot.
whoever thinks this is "neither a positive or negative" mutation is stupid...a LARGE portion of the population either has blue eyes OR carries the gene for blue eyes...i'd call that a positive for breeders everywhere.
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| 16. |
shawn |
2/16/2008 6:58:17 PM MST |
This is freaky to me. Imagine having red eyes if human do evolve in the next 100 years or so |
| 17. |
brett |
2/16/2008 8:16:37 PM MST |
I wish i had eyes, all i have is this lousy t shirt from the eye doctor that says (so they tell me) "Ifi had eyes theyd be blue"!
Thats right. enjoy he gay and lesbian fight!
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| 18. |
UberGeek |
2/19/2008 7:57:41 PM MST |
As mindboggled has already implied, this could more completely be stated as "ALL humans have a single, common ancestor" |
| 19. |
Jennifer |
2/22/2008 5:51:23 PM MST |
See this webpage for a clearer understanding of eye color genetics. |
| 20. |
Jennifer |
2/22/2008 5:52:31 PM MST |
Oops - this website
http://museum.thetech.org/ugenetics/eyeCalc/eyecalculator.html
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