Current Events > PSA: Recessive genes don't disappear when populations cross-breed!

(+) Yeah! (+)

Hey all. I saw a dumb post by what is probably a troll in another topic and I figured I'd clear things out here. I've actually seen this sentiment a lot (not just at GameFAQs), so I'm assuming it's some sort of common misconception.

So what I see people say is that if there's a dominant gene, its recessive counterpart will be wiped out in a few generations if populations "mix". Fairly obviously, this is scare propaganda with some quite racist undertones, intended to discourage procreation between white people and people of color. It's actually been bugging me for a while, because it's completely false. I don't know if it's because people are dishonest or if they just don't know better, but it's quite easy to show that it's false. So I threw together a toy example just to show you.

The most common example used when we talk about dominant and recessive genes is brown/blue eyes. Famously, the allele for blue eyes is recessive in relation to the allele for brown eyes, and you get one allele from each parent. Here's a picture that illustrates it:
https://www.yourgenome.org/sites/default/files/illustrations/chart/punnett_square_eyes_yourgenome.png

So what I did for this little experiment is that I set up two populations, one with just blue alleles, and one with just brown alleles. I set the blue-eyed population at 15% of the total population (10000). I put them together into one big list, shuffle it, and make couples. Each couple has two kids, so the population will remain the same every generation. I let this go on for 1000 generations, and I keep track of the blue-eye alleles throughout. If they were to decline in number over time, we could easily conclude that recessive genes get wiped out by cross-breeding. Let's see if that's the case:
https://imgur.com/a/fJLo7

Nope! I show three different trials (since we have to account for randomness), but I've run this simple simulation tons of times, and there's no real decreasing trend. Over the course of a thousand generations.

Bear in mind, this is a toy example. Populations don't usually cross-breed completely at random, and not everyone gets two kids, etc. Furthermore, there's more to dominant and recessive alleles than the simple blue/brown eyes thing. There's co-dominance, etc. That's why I focused on looking at the recessive gene instead of the phenotype (i.e. which eye color people actually have). In case you're wondering, the phenotype numbers vary a lot less than the above plots, although the dominant phenotype dominates at a higher rate. BTW, this is quite consistent with what we can see in hereditary diseases. They stick around for a long time.

So tl;dr: ITT I show that anyone who says that recessive genes will disappear if you "mix races" is either lying or ignorant.

Questions?
---

Water is wet
---

tc got trolled hard lol
---

foreveraIone posted...

tc got trolled hard lol

Yeah. But I'm procrastinating at work and this was a perfect excuse to do some brainless Python scripting so I just went with it.
---

...bump
---

Isn't skin color co-dominant? Most people concerned about race mixing tend to focus on that aspect. Phenotype over genotype, yo.
---

I think people worry about appearance more than their dna.

Take black Americans for example. Many, if not most have a skin tone that's mocha colored. Many others are very light skinned as well. Almost Hispanic light.

They don't resemble their African ancestors because they are mixed. Their dark skin disappeared due to race mixing. They now have more European features.

This is what supremacists focus on. Looks nor genes.
---

philsov posted...

Isn't skin color co-dominant? Most people concerned about race mixing tend to focus on that aspect. Phenotype over genotype, yo.

Given that the genotype survives, the phenotype won't disappear.
---

scar the 1 posted...

intended to discourage procreation between white people and people of color

Wording like this continues to bug me. So it's white people in one basket, and then every other ethnicity together in another. When you separate us that way, whites are a very small minority.

KazumaKiryu posted...

scar the 1 posted...

intended to discourage procreation between white people and people of color

Wording like this continues to bug me. So it's white people in one basket, and then every other ethnicity together in another. When you separate us that way, whites are a very small minority.

I'm not the one doing it? White supremacy is actually a thing.
---

NINExATExSEVEN posted...

I think people worry about appearance more than their dna.

Take black Americans for example. Many, if not most have a skin tone that's mocha colored. Many others are very light skinned as well. Almost Hispanic light.

They don't resemble their African ancestors because they are mixed. Their dark skin disappeared due to race mixing. They now have more European features.

This is what supremacists focus on. Looks nor genes.

So I threw together some new plots.
https://imgur.com/a/H99Wv
The point is that even with co-dominant alleles, there will be a sustained population of individuals with recessive alleles from both parents. And in the case of America, where white people far outnumber black people, it will be a big majority. So they still focus on literal lies.
---