Genetics questions

I was actually thinking about her eye color😁

but honestly, seeing how my mom turned out, I guess I shouldn't even be surprised😬

I really need to weigh in on this whole eye color debate—honestly, the idea that it all boils down to one single gene for blue or brown eyes is such a massive oversimplification. That’s the kind of stuff they teach middle schoolers just to make things easy, but it completely ignores the reality of green, gray, or hazel eyes. It isn't just one switch; there are at least three different genes at play here. Two of them handle the spectrum of brown, blue, and green, while that third one involves some kind of brown dominance that scientists don't even fully wrap their heads around yet. So, when I was digging into inheritance patterns—since my husband has green eyes—I found a site explaining these three genes that mentioned it is actually POSSIBLE for two blue-eyed parents to have a brown-eyed child. It's incredibly rare, sure, but it totally contradicts those basic biology lessons we all sat through in school. And don't even get me started on the weird cases where someone has heterochromia—like one blue eye and one brown eye—I actually personally know someone like that! At the end of the day, if you want any real certainty about parentage, you aren't looking at eye color; you're looking at a DNA test.

Carol Jackson45 said:Not happening. That's just basic genetics and logic.

Yeah, I can. Your "model" kind of assumes that simplified Mendeleev genetics apply everywhere, which isn't really true.
It also assumes the pattern is totally uniform across the whole surface, which... yeah, also isn't right.

I agree—blue-eyed parents can't have a child with brown eyes, whereas brown-eyed parents can certainly have kids with blue, green, or even violet eyes.🙂

Basically, people who carry the specific gene for blue eyes on both chromosomes (15 and 19) can only pass that blue trait down to their offspring. On the other hand, those with brown eyes often carry recessive genes for blue or green, which explains why they can have blue-eyed children.

I think we tend to overcomplicate the whole eye color thing... It’s really just about the lack of melanin (yellow and brown pigments) and how it's distributed across the anterior iris. Green eyes are essentially "blue" eyes, just with enough pigment to change the hue without turning them fully brown.

When someone with blue eyes suddenly develops one eye that turns green or brown, it's a matter of pigmentation. For some unknown reason, the eye starts "filling up" with brown melanin. There isn't a known gene for this specific occurrence, though some believe it might be a form of protection—since eyes with less pigment are generally more sensitive and prone to issues.

...establishing paternity ☕

My wife and I both have brown eyes, but our two-year-old has these stunning, deep blue eyes. I was wondering—is it likely his eye color will change as he grows, or is this just how he’s going to look?

Brenda Barnes16 said:Basically, people with blue eyes on both chromosomes (15 and 19) who carry that specific eye color gene only pass down that one gene (meaning they can only pass on blue eyes). But since people with brown eyes often carry hidden genes for blue or green, that’s why you see brown-eyed parents having kids with blue eyes.

Sorry, but that whole thing about two loci determining iris color comes from a study published like 30 years ago 😉 (Brues et al., 1975)
In this article from 2003, they actually looked at 6 different genes involved in iris pigmentation, and they even mention 5 more regions.

On this site, you can find a simplified diagram for predicting eye color using those 6 genes.

pikas said:My partner and I both have brown eyes, yet our two-year-old has stunningly bright blue eyes. Will the color shift again, or is this permanent?

My father’s side of the family is entirely blue-eyed, including my dad. My mother has green eyes (her mother was blue-eyed, while her father had dark brown, almost black eyes). Personally, I had vivid blue eyes until about age six—my dad’s influence, I suppose—before light brown pigment began accumulating around my pupils. Eventually, the colors blended into a faded shade of green.
Is it not fascinating how genetics works? Back then, my parents took me to an ophthalmologist who couldn't find any underlying pathology. He simply confirmed my vision was normal, though I wore glasses for farsightedness at the time; I fail to see any correlation between the two.

Ethan Price81 said:Basically...

So, what's the dominant gene for hair color?

Like, can a kid with a blonde dad and a blonde mom (who leans towards brunette) end up with black hair?

Because if black is dominant, then if neither parent has black genes, it shouldn't be possible, right? Unless the dad isn't actually the dad...

Hair is actually a bit simpler than paternity stuff.

It all comes down to how much eumelanin (for dark tones) or pheomelanin (for red tones) you have. To put it simply, hair color is kind of a quantitative thing—people with dark hair just produce more enzymes that make eumelanin. Since we aren't really looking at pheomelanin here, I'll just stick to eumelanin.

There are four independent genes responsible for making eumelanin on chromosomes 3, 4, 10, and 18. Each one has two alleles: functional and non-functional. If we label them "E" and "e," then someone with blonde hair might have a genotype like EEeeeeee (two functional alleles), light brown could be EEEEeeee (three functional alleles), and black would be EEEEEEEE, and so on. Since these alleles are inherited independently, a kid from those parents mentioned above (EEEeeeee and EEEEeeee—so, blonde and light brown) could theoretically—not talking about exact odds here—have a genotype like EEEEEEEEe, which results in pretty dark hair.
So, it doesn't necessarily mean someone's cheating. 😉

The hair didn't fall out, and the baby actually ended up with a darker complexion...

Neither the mom nor the dad have dark skin...
🤣

Now you've gone and confused me 🤔 My father has blue-green eyes, my mother has blue ones, and yet I ended up with brown—so I guess I really am their kid after all 😕