Genetically impossible? Two blue-eyed parents having a brown-eyed child?

[jread]

My wife's aunt has blue/green eyes and her husband has pale blue eyes. Their son has blue eyes but their daughter has very dark brown (almost black) eyes. They whole family says that there is no way the girl has a different father, but I'm not sure I believe it. Everything I have ever learned about genetics tells me that there is no way two blue-eyed or green-eyed parents can have a brown-eyed child. Blue and green are recessive, with brown being dominant over both. Now, it will work the other way around, but you can't go from recessive to dominant with eye color (as far as I know).

Is something like this even possible? Is there something I don't know? Right now I'm trying to figure out how:

Parent 1: bb
Parent 2: bb

Could result in:

Child: Bb

[meshou]

It's possible.

It's also possible they either adopted or got other fertility help which they felt wasn't any of your business.

[jread]

It's possible.

It's also possible they either adopted or got other fertility help which they felt wasn't any of your business.

Interesting article, thanks

I know the daughter isn't adopted because she has many of the same features as her mother... except for the eyes of course.

[ApeTheDog]

Another genetic possibility is for the two parents to have the child, but for it to have been conceived by another man.

[tatsutahime6]

It's possible.

It's also possible they either adopted or got other fertility help which they felt wasn't any of your business.

This article does a decent job of squaring things up in laymans terms, but another thing you must take into account is that both parents aren't truly blue-eyed. There are actually three pigments involved in eye-color: blue, brown, and yellow, the latter of which contributes to the occurence of green/hazel eye colors. As at least one parent in this scenario has a gene for producing the latter pigment, it is possible that this has contributed to the darker eye color of the child in question.

As to date, I believe that at least 8 different alleles have been discovered that play a role in eye color, including genes that are responsible for producing melanin, those that are responsible for controlling the amount deposited in tissue, and those responsible for breaking it down, etc. If my memory serves me correctly, a grey/grey-green eyed person actually carries the gene for brown eyes (although I'm not positive about this), but their body doesn't produce/deposit enough of the melanin for the eyes to appear brown. If this is correct, then a grey/grey-green eyed person could in theory mate with a blue-eyed person (who has a gene for high melanin depositing) and produce brown-eyed offspring.

Of course, it has been years since I studied genetics, so don't take my word for it... And it wouldn't hurt to take a closer look at the mailman's eyes next time he comes around.

[htb]

Jread's question is whether genetics could dictate a child conceived by his wife's aunt and her husband to have dark brown eyes.

There are believed to be some exceptions to Gregor Mendel's conclusions, apparently including blue-eyed parents delivering a brown-eyed baby, and Tatsutahime's remarks on subtractive color would support this. I am not familiar with the logical basis for it, though, and my gut reaction -- especially for dark brown -- would be one of suspicion.

[NoahFence]

Of course, it has been years since I studied genetics, so don't take my word for it... And it wouldn't hurt to take a closer look at the mailman's eyes next time he comes around.

Ivy and I have brown eyes, both our kids have blue eyes, and you would be simply fucking amazed how many garage-geneticists there are out there who chuckle knowingly in this smug sort of "I know your secret and the mailman's too" kind of way. And if you tell them "No, your knowledge of genetics is shit", they laugh and interpet it as you trying to lawyer your way out of what they now know to be true. The funniest thing is, brown-eyed parents being unable to have blue-eyed children isn't even the "conventional wisdom", it's the other way 'round.

This right here is a flawless example of a solid scientific "fact" that everyone "knows" turning out to be misconceived horseshit, and I loved reading it. I love wondering what other basic assumptions we have right now that are patent crap, and how many years it will be before we are looked back on by our decendants as primitive screwheads.

[htb]

It's not uncommon for two brown-eyed parents to deliver blue-eyed children, and in fact accepted rules of inheritance explain such a thing.

[MacGuffin]

Moved.

And in the future before starting threads, it'd be nice if people spent just five minutes doing some basic research.

[Ivy]

It's not uncommon for two brown-eyed parents to deliver blue-eyed children, and in fact accepted rules of inheritance explain such a thing.

Yeah, we're aware of that. I've given a few on-the-spot genetics lessons to people who wink-wink-nudge-nudge when I tell them no, Daddy has brown eyes too.

Edit: evidently, I need a genetics lesson myself-- I had been telling people about Mendelian genetics when they questioned the parentage of my kids. The links in this thread suggest that what was "accepted scientific fact" when I was in college just a handful of years ago is no longer accepted as fact.

The funniest thing is, brown-eyed parents being unable to have blue-eyed children isn't even the "conventional wisdom", it's the other way 'round.