Are my brothers adopted?

June 21, 2009 6:11 PM

Both of my parents have brown hair, brown eyes. I also have brown hair, brown eyes. My two older brothers have blond hair, blue eyes. Is that strange? A reason to think they may be adopted?

We've joked before about them being adopted, but a recent This American Life episode made me think it could actually be true and I'd have no idea. I did a little research and found something about baby hair color from parents.com: "your baby's hair can turn out to be a beautiful range of shades between your hair color and that of your partner." That suggests it's odd to have a baby with a different color hair than both parents. Off the top of my head, I can't think of anyone I know with two parents having the same hair color and the child with a different hair color. On the other hand, I've never really paid attention to hair color.

Other than the hair and eye color thing, I have no reason to believe my brothers aren't biologically related to me. Is that odd enough to be worth bringing up to my parents or brothers?

posted by scottreynen to science & nature (22 comments total)

Is that odd enough to be worth bringing up to my parents or brothers? If you really want to offend them, yes.
posted by liketitanic at 6:13 PM on June 21

A reason to think they may be adopted?

No.
posted by fire&wings at 6:14 PM on June 21 [2 favorites has favorites]

Also, Wikipedia explains how it's possible:

"One gene, (brown/blonde) has a dominant brown allele and a recessive blonde allele. A person with a brown allele will have brown hair; a person with no brown alleles will be blonde. This explains why two brown-haired parents can produce a blonde-haired child."
posted by liketitanic at 6:15 PM on June 21

Off the top of my head, I can't think of anyone I know with two parents having the same hair color and the child with a different hair color.

My parents, both varying shades of brunette, have a blonde child, a redhead child, and a brunette child. Genes are funny.
posted by ThePinkSuperhero at 6:20 PM on June 21 [1 favorite has favorites]

My parents both have brown hair and brown/hazel eyes. My sister has light brown hair and green-blue eyes. My brother has blond hair and blue eyes. I have brown hair and green eyes. None of us are adopted. My own son has white-blond hair and blue eyes. It happens.
posted by Kangaroo at 6:21 PM on June 21

I know a number of brown haired pairs who have blonde or red-haired children, and brown-eyed pairs who have blue-eyed children. I grant I haven't done DNA testing, but I'd bet against it being anything other than luck of the genetic draw.

That said, I'd probably start being obnoxious to my siblings and bring up switched at birth/milkman/adoption scenarios, but not because I believed it to be true. You would know better if this would be funny or offensive in your family.
posted by jeather at 6:23 PM on June 21

It's recessive genes. What do your grandparents and great-grandparents look like? (for the record, both of my parents have brown hair and eyes. I have green eyes and light brown-dark blonde hair. My sister has darker hair than either of my parents and blue eyes. We're both certain of our pedigree.)
posted by Green Eyed Monster at 6:23 PM on June 21

Eye color and hair color is (AFAIK) more complicated than simple one-gene tables.

However, if your parents display a dominant simple characteristic, then we can't know what an offspring will have. A dominant gene would mask a recessive gene that does indeed exist.

Aa + Aa = aa or Aa or aA or AA

If your parent both display what should be recessive, then both of their genes each are known to be recessive. A child must have both recessive genes, and would display it the same way.

aa + aa = aa (or aa or aa or aa)
posted by cmiller at 6:29 PM on June 21 [1 favorite has favorites]

My parents both have dark brown hair. Two of my siblings also have dark brown hair, I'm a redhead, and our other sibling is blonde.
posted by firei at 6:37 PM on June 21

Gonna go ahead and jump on the Train to Anecdote and add that while my son is blonde with blue eyes, both his father and I are brown haired and brown eyed. There is also absolutely no question of who the DNA donors are. Recessive genes are the answer, and having a geneticist in the family helped explain that a looooooooooong time ago.
posted by msali at 6:44 PM on June 21

start being obnoxious to my siblings and bring up switched at birth/milkman/adoption scenarios

I've been doing that for 20 years. Now that I know blond is a recessive gene, I have some new material.

What do your grandparents and great-grandparents look like?

I'm not sure. I don't know much at all about my great-grandparents, and my grandparents were all gray before I was born. From what I remember (with my exceptionally bad memory) seeing in pictures, I believe my mother's father had blond hair and the rest had brown.
posted by scottreynen at 6:50 PM on June 21

While there's no doubt I am my parents' child due to looking so much like my siblings, ALL four of my immediate family (mom, dad, sister, brother) have dark hair brown eyes while I have blonde hair and blue eyes. ( I was called the milkman's kid all my life)
posted by beccaj at 6:54 PM on June 21

Can two blue eyed parents have a brown eyed child?
posted by solipsophistocracy at 6:59 PM on June 21

Solip, my understand is that no, that is not possible. Two brown-eyed parents can have a blue-eyed child, but two blue-eyed parents cannot have a brown-eyed child. Now, this may be too simplistic, because eye color is not controlled by a single gene (as I was taught in middle school biology, and probably most folks were as well). But I still think it's the case.
posted by Conrad Cornelius o'Donald o'Dell at 7:18 PM on June 21

Brown-eyed parents can have blue-eyed kids. Blue-eyed parents cannot. Genetics Cliff Notes: Blue eyes say "love me or I'll die." Brown eyes say "love me or I'll kill you."
posted by applemeat at 7:20 PM on June 21

Can two blue eyed parents have a brown eyed child?

Yes, they can.
posted by gudrun at 7:25 PM on June 21

Brown eyes are not strictly dominant over blue.

"Although not common, two blue-eyed parents can produce children with brown eyes," says Richard A. Sturm, a Principal Research Fellow at the Institute for Molecular Bioscience at the University of Queensland in Brisbane, Australia.

Eye color is a complex trait that depends on the state of several interacting genes. The gene that usually decides the issue (blue eyes or brown eyes) is the OCA2 gene on chromosome 15. But it comes in different strengths. A person with a weak form of the OCA2 gene will have blue eyes. Likewise a person with a strong form will have brown eyes.

The plot thickens, though, because an individual also has other eye-color genes that each has a say in the final eye-color outcome. For example, if one of these lesser genes is strong, it can make the weak form (blue) of OCA2 work much more effectively — almost like the strong form (brown). Then the eye color may be a light brown or muddy grey. In fact, the resulting color can be any shade of brown, hazel/green, or blue depending on the strengths of the interactions.

Yes, Frederick. Two brown-eyed parents can have a blue-eyed child. In fact, this is fairly common.

See also here.
posted by jeather at 7:26 PM on June 21 [2 favorites has favorites]

My father's hair was black. My mom's hair was dark brown. They had three kids and all of us are redheads.

The genes are in both family lines. It's a double-recessive, so the chance of hitting it three times is 1/64, which isn't really all that long. Improbabilities of that order happen all the time in the real world.

"Odds against" doesn't mean "impossible".
posted by Chocolate Pickle at 8:29 PM on June 21

Well, my mother was a woman, but I came out a boy, so there's some scandal in my family as well.

the scandal is that they had a son who does not understand genetics
posted by davejay at 8:41 PM on June 21 [8 favorites has favorites]

Both of my parents have brown hair and brown eyes. I have red hair and hazel eyes.

My husband is a blue-eyed blond. We have one daughter with blonde hair and blue eyes, and one with brown hair and brown eyes.

Depending on which side of the family we're hanging out with (my husband's cousins both married redheads so I fit right into the family pictures), somebody always looks like a total oddball freak.
posted by padraigin at 8:53 PM on June 21

My brown/black haired, brown-eyed grandparents had five super-blond, blue-eyed kids.
Hows that for long odds?


But yeah, it's probably more complicated than the wiki page, as eye colour etc actually appears to be controlled by multiple genes, and blue eyes may not always be recessive - there seems to be some oddly strong blue-eyed genes in the family.
*shrug*
posted by Elysum at 9:43 PM on June 21

My mom has brown hair and brown eyes; my dad has (well, had, he's bald now) blond hair and blue eyes. My youngest sister is blond with blue eyes; my other sister has strawberry blond hair and hazel eyes; I have brown hair and brown eyes, and my older brother has brown hair, one brown eye and one green eye. None of us were adopted.

Looking at us, though, you'd never doubt that we were related, even if our hair and eye colors differ: our faces all have the same shapes, our eyes and noses are all shaped the same, we've all got small mouths with thin lips. Is there no other family resemblance between you and your brothers at all?

(You might want to check out another episode of TAL, The Ghost of Bobby Dunbar, which deals with similar issues to the one you mentioned above.)
posted by aparrish at 8:43 AM on June 22