Thursday, March 27, 2008

resisting the kelly clarkson reference

i have hazel eyes and since i went on spring break they have changed from their winter browny to their summer greeny color. i like the greeny color better because it fluctuates shade more and has a ton of colors in it. sometimes in winter they'll get green if i wear a bright color or or something, but not too often. and usually i don't even notice.

i thought it had to do with the light around me being reflected in my eye but wasn't too sure so i googled. apparently no one else really knows, either. but here's geneticist Rick Sturm's explanation (from USA TODAY, written by April Holladay)

the bottom pic i found when i googled "hazel eyes" and shows a range of eye color that i thought was pretty.

Hazel is in the eye of the beholder; more on memory


Q: What exactly are hazel ey
es, and what color are they? Rita Lichtenburg South Africa

A: It seemed like a simple question, when I first read it. Then I went to various sources, and found no consensus.

Hmmm. This is a question for a world-renown expert.

"The question of Hazel eye colour has haunted the literature," muses geneticist Rick Sturm, principal research fellow at the University of Queensland in Australia. "The fact is eye color (like skin and hair color) is a continuous spectrum — from the lightest shades of blue to the darkest brown/black."

Moreover, it's subjective. "Visual impressions of colour can change as often as you change the lighting conditions."

Also, hazel eyes, like blue eyes and all light eyes, reflect colors around them, as a pool reflects the sky.

Sturm and his team have studied adolescent twins to determine the genetic underpinnings of eye color. In the course of these studies, he's taken 1,937 eye photographs, and divided the group into three major eye-color definitions. Sixty-percent of the twins fall in the 'blue' category, 26% in 'green/hazel' and 14% 'brown.'

"Surprisingly," 74% of the green/hazel eyes had a brown ring around the pupil. "This major pattern may explain a lot of eye color that is commonly referred to as Hazel."

These statistical findings are unpublished, and not yet accepted by peer review; they "only represent my opinion at this stage" says Sturm.

How do such eyes occur? Certainly the simple model we learned in school about brown-eye color being dominant over blue falls short of an explanation. Indeed that one-gene theory is kaput. There is no single gene for eye color. Now, we know two major genes and other minor ones account for the tremendous variation of human eye color, says Sturm, part of the team making this discovery, reported in 2007.

The gene OCA2 produces a protein that allows the hair, skin and eyes to make pigment (called melanin) that colors these body parts. The more pigment in the eye, the darker it is. Much pigment results in brown eyes; little pigment causes blue eyes.

Furthermore, a change happens fairly frequently to the pigment protein under the control of the OCA2 gene. When the protein changes, its function changes. It makes a different pigment that then colors the eyes green or hazel. Sturm likens this process to "changing a light bulb from brown to green."

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