Posted on 02/25/2007 4:34:29 PM PST by blam
University of Queensland
Date: February 25, 2007
No Single Gene For Eye Color, Researchers Prove
Science Daily A study by researchers from The University of Queensland's Institute for Molecular Bioscience (IMB) and the Queensland Institute of Medical Research is the first to prove conclusively that there is no single gene for eye colour.
Says Dr. Rick Sturm, the IMB researcher who led the study: "... the model of eye colour inheritance using a single gene is insufficient to explain the range of eye colours that appear in humans. We believe instead that there are two major genes -- one that controls for brown or blue, and one that controls for green or hazel -- and others that modify this trait." (Credit: Image courtesy of University of Queensland)
Instead, it found that several genes determine the colour of an individual's eyes, although some have more influence than others.
Each individual has two versions of a gene, inheriting one from each parent, and these versions can be the same as each other or different, Dr Rick Sturm, the IMB researcher who led the study, said.
It used to be thought that eye colour was what we call a simple Mendelian recessive trait - in other words, brown eye colour was dominant over blue, so a person with two brown versions of the gene or a brown and a blue would have brown eyes, and only two blues with no brown could produce blue eyes.
But the model of eye colour inheritance using a single gene is insufficient to explain the range of eye colours that appear in humans. We believe instead that there are two major genes - one that controls for brown or blue, and one that controls for green or hazel - and others that modify this trait.
So contrary to what used to be thought, it is possible for two blue-eyed parents to have a brown-eyed child, although this is not common.
Dr Sturm likens the system to a light bulb.
The mechanism that determines whether an eye is brown or blue is like switching on a light, whereas an eye becoming green or hazel is more like someone unscrewing the light bulb and putting in a different one.
The study was carried out to clarify the role of the OCA2 gene in the inheritance of eye colour and other pigmentary traits associated with skin cancer risk in white populations, and examined nearly 4000 adolescent twins, their siblings and their parents over five years.
The findings are published in this month's edition of the American Journal of Human Genetics, and were supported with grants from Australia's National Health and Medical Research Council and the United States of America's National Cancer Institute.
He's had several cycles of color change over the past 30 years.
My grandmother had her ophthalmologist tell her to go to her doctor, based on iris changes, because she had uterine trouble... She had cancer, which they successfully treated with radiation. That was in the late 60's.
There's a whole field of alternative health diagnosis called iridology which analyzes and diagnoses ailments using markers and changes in the iris. I've knows a few New Age folks who swore by it.
So you *are* a Tigers fan, yes??? ;-P
My mother is Rh neg & has brown eyes, so I don't think the traits are linked. Her maternal line was Prussian & her paternal line was half Norwegian, half Swedish. The brown eyes were from the Prussian side.
This still does not genetically explain why brown-eyed people are intellectually superior to blue-eyed people....?
Interesting.
My parents both have green eyes, but my brother has blue eyes and I have some weird color the DMV lists as "grey" but my friends describe as "dirty white" or "ice cube." They are VERY light in color, and I have a VERY dark ring around the iris.
Hubby's folks are green-eyed and hazel-eyed. BIL has green eyes, hubby has light brown.
Both our boys have strangely-colored eyes. Our oldest's are almost orange, while the little one has my whacky color, as does my brother's daughter.
We must have some really wild genetics going on all over the place around here, but I find this topic fascinating. When you have a big extended family such as ours, I love to watch and see where stuff like eye color pops up.
Thanks for posting this,
Regards,
The cancer was noticed because of certain spots in the iris, I think. So no worry there.... ;-)
My kids are determined I'll be a Red Wings fan! I saw the Storm beat the Charlotte Checkers just last week. LOL
Everyone in my extended family have bright blue eyes.
My husband and I have hazel eyes, and were shocked when we produced three blue eyed children. The fourth has brown eyes, and then we were shocked that they weren't blue. :)
Not us...we've got every color in the rainbow. We also have a lot of red hair (my brother and I are both auburn-haired), but neither of our parents are. I've got aunts and uncles on both sides with red hair, and my maternal grandfather was a redhead, but still...that red hair shows up unexpectedly sometimes!
My SIL has one bright blue eye and one eye that is half blue and half brown. Now THAT'S wild looking. It was the first thing I noticed after the surprise of meeting a woman even taller than I am. No red hair, though, poor girl.
Thanks again for the fun thread.
Regards,
Did their daddy have a lot of blue eyes, or do the kids just sorta win and lose 'em, like marbles?
;-)
What an interesting mix. We are all blue - every one of us
My mom and dad both have blue eyes.
I and my two brothers have blue eyes.
My son's father has blue eyes and my son does as well. Son married a blue eyed gal but no children yet but they will have to be blue I believe.
My one brother married a blue-eyed woman and his daughters both have beautiful blue eyes.
My other brother never had children so will never know.
Every one of my aunts and uncles on both sides have blue eyes.
Somehow methinks the reality of physical manifestations of genetics does not work according to our ignorantly assigned categories.
Interesting, will read about it. Thanks.
Thanks.
I'll look at that book.
"Maybe you should ask them more politely."
Really? Is that all?:) I've been trying to give one gas and all I smell is soap bubbles.
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