Question about breeding, CAS, and genetics

[Roux]

Fellow redhead here... my father has brown hair/blue eyes, my mother has blond hair/green eyes. They had three redheaded children with blue eyes. Not as unexpected as your family genetics, but unusual in that all of us got red hair. We all had similar hair color as children, but one brother has faded to a bright strawberry blond, the other brother to a dirty blond with a reddish tinge. My hair has darkened some with age, so it's not as fiery as it once was, but it's still definitively red.

My mother's sister has red hair, and she married a man with very dark brown hair (Eaxis would call it black). They had three children: two have blond hair, one has brown. We always joked that we should just swap the kids in the two families.

[Zazazu]

Funny how the hair on my head decided to fade out while my facial hair didn't.  The "other" hair didn't fade out either.  ifyaknowwhatimean   

The whole world knows what you mean. My dad still has nearly pure black hair on his head, but a full gray beard. I'm not sure about the "other" hair, and I don't exactly want to know, but he's pretty much a hairy ape and all his other body hair is still black.

Blue eyes were the only eye color in my family for the past three generations. So obviously I got them. That's where one of my favorite sim-genetic comments comes from ("a real crapshoot, that") when two same dominants breed or two homogeneous recessives breed. My grandaunt used to make comments about all the new babies' blue eyes being a huge crapshoot.

[AuKestrel]

I think sometime after I graduated from college, I read that new things had been learned about genetics that made predicting hair and eye color far more complex.  Apparently, it's actually possible for two blue-eyed parents to have a brown-eyed child.  I don't remember the mechanics of how and why it can happen, though.  That might have something to do with it -- or there might have been too many cases of kids suddenly discovering that "daddy" was really the postman.   

It's simply not possible for two blue-eyed people to have a brown-eyed child. But the thing that confuses a lot of people is when they call hazel or green eyes "blue." There are really basically two colours of eyes: brown and not-brown or "with pigment" and "without pigment." Not-brown is blue (or grey if you live in Europe *g*). "Brown" is every other colour: hazel, brown, green, blue-green, red-brown, gold, what-have-you.

If two blue-eyed people had a brown-eyed child, yes: either "Daddy" was the mailman or one of the parents has very light green or hazel eyes that contain a lot of blue-appearing pigment. But blue eyes basically *lack* pigment and therefore appear "blue" or "grey."

A basic eye colour website: http://www.athro.com/evo/inherit.html

PS: I have brown hair; both my parents have brown hair, my mother's almost black. My grandparents all had brown hair on both sides of the family. The last known redhead in my family was my mother's grandmother. My husband is dirty blond and has a sibling with "gingery" hair but it's not what you'd call red.

Imagine our surprise, therefore, when our first child was a shiny new copper-penny redhead. He's 16 and is still shiny copper penny red (somewhat darker but still a lovely shade of copper-red) and so are his incipient whiskers. His sister was born a dirty blonde that's turning darker as she ages and will probably end up being brown. So the red hair skipped three generations and showed up out of the blue. Probably my father does not carry the ability to allow hair to be expressed as red, since my parents had five kids, including two blondes, and not a redhead among us. Yet my husband and I only had two kids and bam, we got a red head. Not only that, but it's curly too.

Our family joke, since we were living in Germany when he was born, is when people ask, "Where did he get the red hair? The milkman?" we answer, "No, the beer man!"

[BastDawn]

Blue eyed parents, brown eyed kids:

http://www.madsci.org/posts/archives/2000-06/961696074.Ge.r.html

http://askville.amazon.com/SimilarQuestions.do?req=true-blue-eyed-parents-child  This one explains how ANY blue gene can result in brown eyed kids.

http://www.wonderquest.com/brown-eyed-babies.htm

http://genetics.suite101.com/article.cfm/the_genetics_of_blue_eyes

The gist of it all is:

...two blue-eyed parents can sometimes have a brown-eyed child. This shouldn't be possible but does happen. The best explanation is that there is another gene involved.

From the same website you linked:

http://www.athro.com/evo/gen/inherit1.html#uncertainty

Research is interesting! 

[Count Four]

My mother has green eyes, brown hair, my father has blue eyes, light brown hair. Between them, they produced three brunettes, three blondes (hair remains blonde in adulthood), one redhead, and two ash blondes.  All of us except the redhead started out with blonde hair as kids.

Amongus are seven with blue eyes, one with green eyes, and one with brown eyes--and she's one of the colorfast blondes.

So it can happen that two people with 'recessive color' eyes can have a brown eyed kid. But they only managed it one in nine.

[toad]

Is it possible that eye colour also has penetrance issues? 
So it's not necessarily that the milk man is the parent, but more that Daddy (or Mummy) has a brown gene that hasn't shown up, but does manage to work in the child.

[Zazazu]

That's what I had heard, that there is a possibility that someone can have the genes for brown eyes, but display blue because the proteins are somehow blocked by some other condition. So a mom could be Bb, displaying blue due to the proteins being blocked, with the father bb and displaying blue of course. Child inherits Bb.

[AuKestrel]

Research is interesting! 

Indeed!

Almost all of the examples cited, however, have to do with genetic mutations, "gene swapping" or fetal damage during pregnancy. Because of this, I am thinking the possibility of two blue eyed parents having a brown eyed baby because of an incompletely expressed gene  is more uncommon than the other causes.

But you're right and I was wrong: the question, can two blue eyed parents have a brown eyed child, can be answered "yes."

[AuKestrel]

My mother has green eyes, brown hair, my father has blue eyes, light brown hair. Between them, they produced three brunettes, three blondes (hair remains blonde in adulthood), one redhead, and two ash blondes.  All of us except the redhead started out with blonde hair as kids.

Amongus are seven with blue eyes, one with green eyes, and one with brown eyes--and she's one of the colorfast blondes.

So it can happen that two people with 'recessive color' eyes can have a brown eyed kid. But they only managed it one in nine.

That would surprise me less than two blue eyed parents having a brown eyed child, because while green is dominant over blue and brown is dominant over green, green still indicates the presence of melanin and blue is still the absence of melanin. So if there are enough polygenes piling onto the pigmentation (the way they do in the rufus gene in red cats) - which I've always thought was one possible explanation for the great variations in eye colour - then I can see that green could be 'hiding" brown.

At any rate, yes, it is possible - I was wrong.

[gethane]

This conversation has surely turned interesting. And it's such a relief when someone can in a good-natured way say "I was wrong" instead of maintaining an answer or becoming abusive, especially on the internets  So props.