Eye-color Genetics Question

Factual Questions
1

Ok, here’s the deal: I do not know whether I am heterozygous for brown eyes or homozygous for brown eyes. In case you are wondering why it matters to me, I am inquiring about this to better understand the chances of my future children having light eyes or brown eyes. Not that it matters critically, but rather just as a “just wondering” thing.

All data of my relatives’ eye color, simple genotype in parentheses, and country of birth (for ethnic purposes) in brackets, are listed below.

[Russia] maternal grandfather: gray (aa)
[Ukraine] maternal grandmother: hazel (Aa)
[Ukraine] maternal uncle #1: blue (aa)
[Ukraine] maternal uncle #2: gray (aa)
[Ukraine] maternal uncle #3: brown (Aa)

[Ukraine] mother: hazel (Aa)

[Russia] paternal grandfather: gray (aa)
[Ukraine] paternal grandmother: black (AA) - she has an Armenian bloodline so no doubt she is homozygous dominant

[Ukraine] father: brown (Aa)

[America] Me: brown (A?)
[America] Sister: brown (A?)

Using the following Mendelian genetics equation does nothing for me in terms of determining my genotype, except state the obvious–that I am not homozygous recessive.

Aa x Aa = AA Aa Aa aa

It does, however, give me the probabilities that I am homozygous dominant (1/3) or heterozygous dominant (2/3). So odds are that my sister and I are heterozygous dominant. But there is still a big 1/3 possibility that I am homozygous dominant, and I would not be able to have light eyed children.

The Big Question: Is there any other way to objectively determine whether I am homozygous or heterozygous dominant. Is it possible to explore my 15th chromosome pair, locate the OCA2 genes and determine whether one or both chromosomes contain the recessive light-eyed mutation. And even if this was possible do you think I could request lab scientists to check?

Forgive me for the length of this post. If you don’t have a definitive answer, that’s all right, as I can’t seem to find one. All open ideas/input is appreciated. Thanks!

2

It is certainly within the realm of possibility for science to actually have a lab check your chromosomes to determine your eye-color inheritance, but the main problems I see are in time and cost, neither of which you seem likely to want to spend in the (most likely) necessary large quantities, due to the “just wondering” status of your question.

As an aside curiousity, why are you so interested in whether your kids can have light eyes?

3

Thanks for your answer! Very good point about the cost. I don’t think I would be inclined to spend a ton of money just to know my genotype. As for your question, I just think light eyes look nice green, gray, and blue. I like my brown eyes as well, but it would be cool if I had gray ones. And If I had brown-eyed kids, I would still treat them equally to the potential light eyed ones. I was more curious of the possibilities, just as any future parent would be interested in the potential variety of their kids.

4

Damn big of you.

5

Eye color is controlled by more than two alleles, so your basic assumption is wrong.

Also, there is no reason to assume that Armenian = no recessive eye color alleles.

6

A brown eyed person can produce blue eyed off spring, I have a cousin who did …

Actually she has two kids, one brown eyed and one blue eyed. She has blue eyes and her husband has brown eyes.

7

This made me literally laugh out loud, at work. People were staring…:smiley:

8

Yes, that’s just basic genetics. Or rather, it’s basic genetics that some brown-eyed people can have blue-eyed offspring. The OP is already aware of that, and is wondering whether he’s one of the brown-eyed people who can have blue-eyed offspring.

9

Actually, the OP wants to know if he (I thought it was a she) can have “light” eyed offspring, which I think means “non-brown” eyed. Given the eye color of the parents, blue eyes are not an option.

10

Don’t take me for a fool. I am aware that eye color is a polygenic trait involving AT LEAST six genes.

“A study in Rotterdam (2009) found that it was possible to predict the color of eyes with more than 90% accuracy for brown and blue, using just six SNPs (from six genes).”
http://www.sciencedirect.com/science/article/pii/S0960982209005971

However, the OCA2 gene, the more well studied gene, is the one shown to be responsible for the gene switch from brown to lighter colors–blue, gray, green, etc. The other five (HERC2 for example) or so genes determine the melanin concentrations to various sectors and layers of the iris. These genes only matter in considerations of possibilities of blue, gray, and green eyes. I was referring to the single OCA2 gene, which is either mutated or not.

All light eyed people have the exact same mutation in their OCA2 gene and therefore that specific mutation is the difference between light or brown.

“Eiberg’s team then tested 155 blue-eyed people from Scandinavia, Turkey, Jordan and India, looking to see whether they, too, had similar DNA sequences on that gene. To their amazement, they found that each individual had identical DNA sequences in that region of that gene”
http://www.usatoday.com/news/health/2008-02-05-blue-eyes_N.htm

Yes, I am aware of that. But in all fairness, you have got to admit, it is pretty damn rare. By that, it is fair to say, the large majority of Armenians lack the recessive color allele since there are many brown x brown crosses resulting in nearly all brown eyed offspring. The allele frequency of (a) is not zero, but very small.

11

I don’t take you for anything other than what you post.

12

Completely on the anecdotal side:

I come from a long line of people who would screw anything that moved, regardless of color. I married a Scandinavian guy in whose family everybody has light-blue eyes.

My father who is almost-certainly white (you never know), has light-blue eyes too. My dark-skinned but also-mixed mother has light-brown eyes, but her mom had green eyes.

So my daughter has three grandparents with light blue eyes, a grandmother with light-brown eyes, a father with light-blue eyes and a mother (me) with very dark brown (black?) eyes: She got my grandmother’s green eyes instead.

So yeah, one never knows. I wouldn’t have bet on that.

13

I really wish they’d quit using eye color as an example problem in high school biology, because it’s way more complicated than what they teach, and people end up getting really confused when they try to apply it to the real world.

14

The OP’s parents eye-colours are given as hazel and brown (same as me and my wife – although genders reversed from the OP). Our son has blue eyes. (We also both have brown hair, and his is blond).

'Course quite a few relatives on both sides have blond or red hair and blue eyes. (And although the hair on my head is brown my beard… and other hair… is red). :slight_smile:

Although the OP appears to not have much blue in the family (unless gray is also blue) I’m not sure how you reached the conclusion of blue eyes not being possible – could you explain a bit please?

15

:smack: You’re right. I don’t know what I was thinking.

16

Interesting…both you and your wife are Aa, heterozygous for the brown gene, and are also both carriers for the blond hair gene. Aa x Aa = AA Aa Aa aa, and aa is blue eyes, so your son got the 1/4 chance of getting blue eyes. He’s lucky! Also, I must say, that’s pretty badass to have a red beard. Reminds me of the pirate haha.

He is half right… When I have a daughter or a son, he or she will receive a set of my genes and a set of my [future] wife’s genes.

Since the a great majority of the light eye alleles in my family are from relatives with gray eyes, I would probably, but not certainly, be carrying an allele for gray eyes, that is, if I happened to be an Aa eye type–a carrier of the light eyed gene.

But the second set of genes, will come from my wife, and that all depends on what her eye color and her relative’s eye colors. And that may or may not result in blue eyes. To make a good guess as of a child’s eye color, you would have to look at the different eye colors in your and your partner’s siblings, parents, grandparents, aunts, and uncles. Even so, eye color is a fairly complex thing involving many genes so it is quite hard to predict. With that said, you can never say never with predictions just as you can’t be certain either. Take for example post #12 above by Mighty_Girl, whose daughter got her [maternal] grandmother’s green eyes.

The difference between blue and gray eyes is it’s more of a dimmer, more faded out version of blue. I think it looks cool, though. Although they are very similar, they aren’t the same as blue eyes, both genetically and physically. The science behind it is very interesting though…

The color of the iris is determined by the refraction of light from the persons eye. People with brown eyes have lots of melanin to absorb many frequencies [colors] of light, so not much is reflected back, making them look dark/brown. People with blue eyes, have a harmless mutation that stops them from producing as much melanin in their iris, changing the colors of light that are absorbed and reflected by their eyes. Blue eyes and gray eyes tend to absorb more red light and reflect more blue light, and so they appear blue or gray. The iris has two layers: a top layer and a bottom layer. The physical difference between blue eyes and gray eyes is that with blue eyes the top layer of the iris lacks melanin and reflects blue light first as it hits the eye so it looks definitively blue. With gray eyes, the top layer has more pigment than a blue eye’s top layer so the light is dimmed and partially absorbed when it hits the second, bottom layer, which resembles the top layer of a blue eye, and is reflected back through the darker top layer achieving the ultimate result of a dimmer blue/gray eye. Yeahhh it’s kind of complex haha, but I hope I didn’t confuse you :wink:

Here’s a gray eye:

And a blue eye for comparison:
http://www.flickr.com/photos/weirdcolor/4088940371/

17

In school I remember being taught that two blue-eyed parents cannot produce brown-eyed offspring, but I understand this is incorrect. I’ve also seen this “fact” being reported at Science Daily:

18

You are right. Although, two blue-eyed parents can produce a brown-eyed child it is very rare. I suspect that ScienceDaily reported that for the sake of probability: two blue eyed parents will very probably produce a blue eyed child. Although I love reading ScienceDaily and other popular science news sites, the thing that sometimes bothers me about them is that they tend to oversimplify things at times, such as the case above. But I guess they didn’t want to say that two blue-eyed parents can rarely have brown-eyed children, because that would require them to explain how exactly it is possible, while jeopardizing the underlying argument of the article. This would just lead to them putting an article within an article and confusing readers.

Since eye color is controlled by many genes, all of those genes can come into play in surprising ways to result in the final eye color. The OCA2 gene is the main gene switch from brown to blue, but it interacts with other genes to affect color. So the type OCA2 genes of two blue-eyed parents can interact with other genes to produce [from most common to rarest]: blue/gray, green, hazel, brown

Very helpful article on this: http://www.thetech.org/genetics/ask.php?id=332

19

I was responding to this

portion of the original post. :wink:

20

Pretty much what we figured – both our families have a lot of red hair and blue eyes but also some members who have a darker tone (almost olive skin, dark hair, etc – a fairly typical Welsh “look” that’s almost a bit Spanish / Latin). My wife has one blond blue-eyed brother and one with the Welsh look. My Dad had red hair (when younger) and has pale freckled skin, but my mother could tan almost nut brown.

Heh – tell him that in an NZ summer when he burns like crazy. :slight_smile: (OK, not technically because of the blue eyes, but…)

:smiley: I think it’s interesting to be able to have a beard colour that’s different from the hair right next to it. Genetics is weird. :slight_smile:

Oh, OK… I didn’t know that. Cool, thank you.