Posted on 01/30/2008 2:10:37 PM PST by decimon
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.”
Works for me. What I want to know is why I was born with blue eyes then when I was three they changed to brown and now they are hazel......
Is that the Atlantis influence??
There's a whole lotta mutatin' goin' on here. ;-)
I don’t think David Bowie had a concussion, but I do remember that there was SOME kind of accident years ago, in childhood I believe. If you look closely, his eyes are in fact the same color, but because the left pupil is so dilated, it appears to be a much darker color.
Regards,
Regards,
NOT GUILTY! Oh wait, that’s not this kind of thread. Oh well, either way, she’s definitely not guilty...nasty or not.
BTW my Father has green eyes and my Mother had blue. All their five chileren are either blue or green eyed.
I agree that girl is very pretty. I wouldn't say the prettiest I have ever seen but not too far from it.
[Unless the hospital swapped babies!]
Lol, my kids all look alike. My mom had blue eyes.
THere is no such color as “green” in mammals. Human “green” eye color is actually a mixture of brown and blue. If you look very closely at a green human eye, you will see light brown patches or specs intermingled with blue patches or specs.
“green” results when the blue outnumbers or overpowers the brown. Hazel results when the brown outnumbers the blue. Blue-green is when the brown is almost non-existant.
I don’t know what the technical explanation is for grey or steel blue eyes...or the rust brown/red eye color that is common in redheads. THe red color is most interesting to me because it seems to be exactly the same shade of rust-brown as the freckles on the face of some natural redheads.
Sometimes the percieved eye color changes with the change in intensity of light. I once knew a mediteranean guy that had dark brown eyes indoors, but in direct bright sunlight his eyes changed to a brilliant true baby blue. It was freaky.
No. You are a mongrel. A cur is a class or family, like spaniel, molosser, or terrier. A mongrel is a mix.
I once knew a girl ( a truly beautiful natural blonde) whose eyes were partly blue and partly brown, not mixed but half one color and half the other. Actually it was two thirds blue and one third brown. I took quite a few pictures of her and her eyes really were striking.
She told me her eyes were not as uncommon as one would think as she had run into several others with the same type of eyes.
Wow, Kristin really is a looker.
Kentucky?
I had a grandfather with one pure blue eye, and the other one pure blue with a very well defined patch of dark brown...the brown patch was about 20% of the iris. If you looked at it just right in just the right light, it appeared he had an oblong shaped pupil.
Didn't want to show her face but this is what her eyes looked like.
The word cur has always meant a dog of mixed breed, I thought. One of our dogs is a Black Mouth Cur, she is a hound but it is not a registered breed.
Well, now I’m going to have to look it up.
To me “cur” meant less desireable or less useful, lower quality, etc. But NOT mixed breed. A cur dog, as I understood it, was a class or family of dog that was incompletely domesticated...hence the less useful/quality meaning. Cur dogs are headstrong and independent and less controllable. Very fierce in the hunt and good trackers, but worthless as a flusher, retriever, setter, etc. Poor obedience. And therefore expendable...perfect for hunting bear and boar in packs.
I always assumed cur dogs fell out of favor in the mainstream because it took a heavy hand and frequent use of a whip to keep them under control. That and the fact that they were about as expensive to purchase as a plain old yellow tabby house cat. There’s no bragging rights to owning one. A german shorthair, or english pointer commands a high dollar price and is quite a status symbol among hunters...and displays impressive obedience. Such dogs would never be put at risk chasing bear or boar.
GGG, Genetic Genealogy ping
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