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ArtiqueFox's avatar

Is it possible for two blue-eyed, blonde-haired people to have a dark-haired, brown-eyed child?

Asked by ArtiqueFox (974 points ) February 18th, 2010

The dominate – recessive genes responsible for blue or brown eyes were the topic of today’s biology class. Of course we dove in to punnet squares and all that, and we happened to do one with two blue-eyed parents, drawing the conclusion that such a pair can only have blued eyed children.

But, there is one girl in my class that has brown eyes – almost black brown eyes. But both of her supposedly biological parents have blue. She’s creeped out. I’m curious.

Is this possible? What’s going on here?

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31 Answers

Captain_Fantasy's avatar

She might be adopted. That’s not a bad thing.

MissAnthrope's avatar

Yes, it’s possible..

Eye color is not the simple decision between the brown (or green) and blue versions of a single gene. There are many genes involved and eye color ranges from brown to hazel to green to blue to…

How does eye color work? Eye color comes from a combination of two black and yellow pigments called melanin in the iris of your eye. If you have no melanin in the front part of your iris, you have blue eyes. An increasing proportion of the yellow melanin, in combination with the black melanin, results in shades of colors between brown and blue, including green and hazel.

What we are taught in high school biology is generally true, brown eye genes are dominant over green eye genes which are both dominant over blue eye genes. However, because many genes are required to make each of the yellow and black pigments, there is a way called genetic compensation to get brown or green eyes from blue-eyed parents.

(Link)

trailsillustrated's avatar

it occurs often. read about the heredity and sweet peas.

ETpro's avatar

Brown eyes are dominant and blue recessive. Likewise dark hair dominant and blond recessive. So other than the shading variations of eye color @MissAnthrope mentions, no—it would require a genetic mutation. I would guess your Biology teacher is looking for that understanding of dominant versus recessive genes. The reverse, tow brown-eyed brunette parents, could easily have a child with blond hair and blue eyes if each happened to contribute the recessive gene for that.

If that’s where your teacher is going, and they aren’t so high-and-mighty as to hate correction, point them to the Wikipedia Article on eye color.

Just_Justine's avatar

yes grandparents genes also count but in a lower ratio. but possible.

hug_of_war's avatar

The genetics you learn in high school is REALLY watered down.

chicadelplaya's avatar

Sure it is. I have some friends who both (and most of their families) have dark hair and dark eyes, and they had a very blond curly-haired, blue-eyed child. You never know what you’re going to get.

ETpro's avatar

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MRSHINYSHOES's avatar

That’s quite possible. I am Asian (Chinese-Japanese), and my sister’s husband is a handsome German fellow. She has dark hair and eyes like me, and her husband is blond with greyish blue eyes. They have two little cute children, a boy and a girl. The girl, who is younger, is a carbon copy of her pretty Mom, with dark hair and eyes, and her older brother is like his Dad, with blondish hair and bluish-grey eyes. I think genetics is a very cool thing. Sometimes what you expect is not what you get.

I have odd colored eyes——one is light brown, like my Japanese Mom’s eyes, and the other is dark brown like my Chinese Dad’s. My complexion is olive, but my sister has very fair skin like my Mom, paler than some white people.

kheredia's avatar

I know a couple who are both brown eyed and dark haired and they had a little blond, blue eyed baby girl. So yes, I would say it is possible.

faye's avatar

The dark combo is dominant so often pass recessive genes and have fair children. It’s the other combination she’s asking about, which is more rare. My ex-husband is dark haired with brown eyes and both parents have blue eyes. We thought she may have fooled around- she may not have been horrid back then.

DarkScribe's avatar

Sure. As long as one of them fools around.

Seriously, I have five daughters, two platinum blonde with blue eyes, one dark honey blonde with hazel eyes and two brunettes. I have dark brown eyes and hair (until chemo turned it white) and my wife brunette with blue eyes. My eyes were blue until I was about eight years old – went dark then. All of my children were born with blue eyes – as I believe is normal. And yes, they are all mine – they all look like members of my own family, not my wife’s.

jerv's avatar

Yes, and it’s simple Mendellian heredity. Just because the parents lack a certain trait, that doesn’t mean that the offspring can’t have it. Some genes are more recessive than others and/or may only express themselves in combination with certain other genes, but it is entirely possible.

Now, did any of that girl’s grandparents have blue eyes? What about the great-grandparents? Their parents? And their parents? If any of her biological ancestors had blue eyes, then it’s possible for her to inherit them.

The only way it would be impossible is if none of her ancestors since the dawn of humanity had those traits, and considering how much interbreeding has occurred lust in the last 100 generations, I think you can see how unlikely that is. By the same token, those who go on about racial purity often have at least one ancestor of another race in their own lineage, making them hypocrites. This is especially true of Americans. Personally, I have at least four different types of European blood and at least 1/64 native American.

davidbetterman's avatar

Of course it’s possible. Didn’t you take 6th grade science yet?

Jeruba's avatar

BUTBUTBUTBUT….

To have blue eyes, you must have a blue-eye gene from both parents. That’s because it’s recessive. So blue-eye genes are all you’ve got. And thus they’re all you have to give.

Now if you marry someone who also has blue eyes, the only genes you can both give to your kids are blue-eye genes. So—your kids have blue eyes.

Parents with dark eyes can carry blue-eye genes. As long as they both give their blue-eye gene to their kids, the kids of dark-eyed parents can have blue (light-colored) eyes.

So the fact that two dark-eyed parents can have light-eyed children does not prove that two light-eyed parents can have dark-eyed children.

Tenpinmaster's avatar

regressive genes? Lol biology is fascinating because you never know what can come out of someone. I think almost anything is possible because life always finds ways to throw stuff out that you don’t expect.

jamcanfi74's avatar

ya why not. I know two dark hair people with a red head, Stuff do skip generations ya know

tragiclikebowie's avatar

Take a look at this study.

Taken from said study; “But now, “contrary to what used to be thought, we’ve discovered it is possible for two blue-eyed parents to have a brown-eyed child,” said lead author Rick Sturm, “though that is uncommon.”

Val123's avatar

Sure. My dad had green eyes, my mom had brown eyes. Three girls, one had brown eyes, us other two wound up with very blue eyes.

Jeruba's avatar

@tragiclikebowie, I see that, but this statement in the next paragraph leads me to wonder about the comprehension of the author of the article:

Until now, brown-eyed fathers might have used the trait as a simple genetic test to confirm whether or not blue-eyed children were really their own.

That false and misleading statement reflects such a gross failure to grasp even the traditional concept that it casts the report in doubt as far as I am concerned. This article is, after all, not the work of the scientist (Sturm) but of a writer of popular science material (Wood), to judge from the context. In interview articles, misquotation occurs easily, and misinterpretation even more easily than that. The interviewer is not the subject matter expert.

Taking Sturm’s statement at face value, I think we must allow the remote possibility of a dark-eyed child as the issue of two light-eyed parents, granting that it is very rare. But there is nothing unusual about the reverse—it happens all the time.

jerv's avatar

Just between my mother and her five biological siblings, there are three different hair colors, and three different eye colors, and my eye color is different from any of them and from my father while my hair color is the same as my father. Now, if we can get siblings with different traits, no two having the same eye and hair color then throw in another person with different genes and wind up with something different from any of them

Don’t forget that genetics is not completely understood yet, especially since some things require a combination of genes as well as a factor of randomness. If it was simple addition then my mother would have the same combination of colors as at least one of her siblings!

ETpro's avatar

@tragiclikebowie The eye color issue is more complicated than a single set of genes. THere are a series that control, so it is quite possible for two bue-eyed partent to have a biological child that has brown eyes. Not common, but possible. But add to that the fact both parents are blond haired, and had a brown haired child, not within the realm of probability. It would have to be a genetic mutation. More likely, it’s not their biological child.

jerv's avatar

One thing that is overlooked here is that people can adopt children that have the same hair/eye color as them as well.

Also, how improbable are we talking here? If the odds of two blue-eyed blondes having a dark-eyed brunette are comparable to being hit by lightning (around 1:600,000 IIRC) then there is a chance (though not a certainty) that the “parents” are adoptive rather than biological.

If, on the other hand, the odds are 10% (to pick a number) then they considerably exceed the odds of me making a typo, yet that is a common enough occurrence that when it does happen, it really doesn’t mean anything.

I won’t even get into the issue of why it matters if they are adopted or not since the original question was, “Is it possible…?”, except to say that if you feed me, house me, and love me for a couple of decades and I will call you Mom/Dad regardless of biology!

ETpro's avatar

Say the blue eye allele is called e and it is recessive. Let’s say E is the brown eye allele. We know it is dominant. Therefore, both parents must have ee to have blue eyes. So without a mutation of that allele, the probability on that base pair is Zero of having a brown-eyed child. However, other genes can impact eye color, so the probability becomes small, but there. Just guessing, but it might be 1 in 1000 or less.

But the hair is more straightforward. If B is the dominant allele for brunette hair and b is the recessive allele for blond, then both parents are clearly bb and that’s that. The probabllity is Zero of them having a brunette child unless there is a mutation of that specific allele. So multiply the probablitties and you are looking at something like winning the big game lottery with the same number 10 times in a row. It’s so unlikely as to be unworthy of consideration.

jerv's avatar

@ETpro If we assume that it’s just a certain gene that controls such things (as opposed to a certain combination) then I agree with you totally, and even if Nature truly is as unknown as my skeptical mind thinks it is, you make a strong case. (+1 GA to you!)

Maybe it would be a little easier for me to swallow if I hadn’t seen so many fucked-up, highly improbable things in my life, but I think that the last paragraph of my previous post renders it effectively moot anyways (at least in my mind) so I’ll go be a nay-saying bastard somewhere else now that you’ve put me in my place here :)

faye's avatar

See the posts above -it is more than one gene.

DarkScribe's avatar

One of my sisters has blue eyes, her husband has blue eyes, two of her children have blue eyes, one hazel and the other brown. It isn’t that uncommon. My wife has blue eyes, both her parents and grandparents on both sides have brown. The parent’s eye colour is indicative of the probability of a child’s eye colour, not of the certainty.

MissAnthrope's avatar

@faye – Exactly.. it’s not simply one gene controlling color, it has to do with shading of black and yellow in the iris. (read the explanation I linked)

ETpro's avatar

@faye Not so. The posts above correctly stated that eye color is complicated because a number of alleles are involved. When it comes to hair color, there are only two genes controling it. One is the Brown/Blond in which, as I stated, Brown is dominant and Blond is recessive. The other controls Red, and isn’t in this picture. So in this particular case, it is that simple.

faye's avatar

I wasn’t qued in on the hair- just glance reading. I know nothing much about the hair and i’m still a little iffy about dark brown eyes from 2 blue eyes, too, alleles and all. I’ll give you hazel eyes, but I need the DNA for believing brown from blue.

darlenebolding's avatar

Genetics are a funny thing Both of my parents had very dark hair my paternal grandmother had blonde hair like me my brother and sister have black hair My mother before she passed away told me that after i was born that she was worried that my dad would think the worst when he saw that i was blonde his father also had black hair well he wasaway for work when i was born they called him to tell him that i had arrived mom told me that he walked into her hospital room carrying me as happy as could be and she told me that she pointed our the hair color and he said something like i know its really pretty isnt it and she said your not mad and he said why should i be and she said because people were talking and he said well my mother had hair the same color and i ended up being the living image of my paternal granmothe in fact my father always carried a picture of both me and my paternal grandmother and when people would make comments he would show them the pictures and say theres your dna test

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