It’s amazing this never occurred to me before, but both of my parents have bright green eyes. My brother’s eyes are clearly blue. Mine are dark brown.
Isn’t that… genetically highly unlikely? Since neither of my parents would have a dominant brown gene. According to this calculator there should be a 0% chance of a brown-eyed offspring when both parents have green eyes. I know that is a simplification. But still, other sources I can find say the chance should be < 1%.
I’ll definitely have to probe my parents about this… but I am really wondering now.
Missed the edit window, but I should rephrase something: I said both my parents have “bright green” eyes but upon looking at a photo, although they are undoubtedly greenish in hue you might be able to call one of them “hazel”, depending on your color perception and what you consider hazel. This could add a kink in the works.
So could a brief and long-buried dalliance by Mom.
If you must know, only genetic testing will confirm or alleviate your anxiety.
Be careful pursuing that path, for satisfying your curiousity may open wounds in others if the conclusion is not the ordinary one–the unpredictability of mother nature.
Yeah, if you click on the “?” in the “allele frequency” box in the calculator you linked to it explains that determination and expression of eye color is likely more complicated than represented by the calculator.
Wouldn’t you also need to know the eye color of your grandparents? Everyone in my family has green eyes except my brother, who has blue eyes . . . as did our paternal grandmother.
Obviously, it helps. But since (in this simple model) green is dominant over blue, it’s not terribly unusual for some blue eyes to pop up in predominantly brown- or green-eyed families. A brown-eyed child popping up in a blue- or green-eyed family is very, very unusual. I don’t know what the real probability would be, but I’d be willing to bet that it’s lower than the rates of adoptions that are kept secret from the adoptees and of nonpaternity. Take some best guesses on those values & do a Bayesian analysis …
Last night I saw an add for some eye-lash lengthening medicine where one of the possible side effects was a permanent increase in brown iris pigmentation. Maybe you were exposed to some chemical while in the womb?
Maybe not, but I think the overall point that factors besides genetics can play a role is a good one (as well as the genetics being somewhat more complicated than it’s made out to be . . . )
Alternative theory: Maybe you’re a mutant. Just be glad you don’t have this guy’s eye problems.
The following is a simplified version of a half-remembered article. Brown pigment is made in the body in several steps. If a blue-eyed person who lacks, say, the genes for the first step, marries a blue-eyed person who lacks the gene for the third step, they could produce a child who has genes for all the steps and therefore has brown eyes.
If green or hazel eyes are involved, I’d imagine it would be even easier to fill in the slots.
