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Green Eyes Continued

I find eye color fascinating, and yet many people take it for granted. In fact eye color is usually dumbed down into two categories, Dominant traits vs Recessive traits. Blue eyes are a recessive trait along with other unusual colors such as green, amber, hazel, grey, etc. You can also be a carrier for other colors which is based on your genetic makeup. Let us try and example to clarify, say Dad has brown eyes, but he’s a carrier for blue, green, hazel. Mom has brown eyes as well, and a carrier for blue, and amber. Brown is a dominant trait and all other colors are recessive. Odds are their children will most likely have brown eyes as well, but since they’re both carriers of the recessive blue, there’s a chance that their children could have blue eyes. When both parents have blue eyes, and you have green eyes. Technically blue and green are both recessive traits, so your parents are both carriers of the green eye color and it just happened to come out in you. For comparison, my dad has blue eyes, mother brown. I have blue/grey eyes, my sister has blue and my brother has hazel. Because my dad has a recessive eye color, he doesn’t have the brown (dominant) trait, and a carrier of at least green, grey and hazel And my mother was a carrier of blue, grey and hazel as well. Keep in mind that eye color, hair color, etc. are a bit more complicated than just dominant vs. recessive but this is how basic biology explains it. Here in the US, where 1 in 6 people have blue eyes, having green eyes becomes rare.
They (Green eyes) are most common in Northern and Central Europe. They can also be found in Southern Europe and North Africa. In fact, Turkey, at 20%, is the country with the largest percentage of green eyes. In Iceland, 89% of women and 87% of men have either blue or green eye color. A study of Icelandic and Dutch adults found green eyes to be much more prevalent in women than in men. Among European Americans, green eyes are most common among those of recent Celtic and Germanic ancestry, about 16%. Source
So countries that have a higher percentage of fair eye color also have more people with green eyes. I might be rare here, but in Scotland for example, I could blend in.
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My Rare Green Eyes

I have green eyes. What you see in my eyes is not the same thing that scientists see in them. The current thought behind green eyes is that a thin layer of yellow pigmentation overlays the "blue" color of an iris, and the result is a yellow color.

The gene responsible for this yellow pigmentation is completely separate from the brown/blue gene; thus, to have green eyes, one must have a low concentration of melanin in the iris and produce the yellow pigment.


Here is a chart that demonstrates how melanin in the front and back epithelia of the iris and the structure of the stroma create eye color. You will notice that the specific combination which is required for green eyes is more complicated.

eye color chart

Of course, we're talking about gene networks here so in reality this isn't cut and dry as I made it sound. If it was, there were be a higher percentage of the population with green eyes.

Eye color is complicated than many may think and the combination required to be born with green eyes is rare. And it has been an area of study for scientist for decades. A lot of people tend to tell me it is because of X or Y, but they are just using layman's terms to try and explain something that they are ignorant about. In other words, anyone who says they know definitively isn't being completely insightful or in other cases honest.

Eye color is highly polygenic and not entirely understood.

A lot of genetics is not as simple as Mendel's pea experiments might lead you to think. Mendel figured the basics out mostly because he picked traits that have distinct, qualitative phenotypes that were only controlled by the expression of a single gene.

This tends to be the exception rather than the rule, but it's still taught in schools because it provides a clear simplified way of explaining the mechanism of why traits are passed on or not.

It is more likely that many different genes play a role in determining eye color (which is a spectrum of colors really, not just "green" or "blue"). While some of the Brown vs. Blue in European populations genes have been worked out (OCA2), the mixtures that make up intermediaries are not entirely clear. What would start off as a binary state becomes very messy when you start adding in 11 other SNPs with incomplete penetrance and variable dominance terms.

As for the rarity, that's just simple population genetics.

The alleles for green eyes, whatever their nature, are simply less common in European and Middle Eastern populations than brown or blue. Hence, they are less likely to be observed.

Since eye color is usually not selected for or against when people choose whom they wish to mate with, the frequency of the "green allele" remains more or less the same. Though I did have a boyfriend tell me once that he was only together with me because of my eye color. That sort of creeped me out and I dumped him a week or so later.