Having a recessive allele from a single human last for 3 millennia

So basically I realized that a plot I'm planning hinges on something that might break the willing suspension of disbelief of anyone who knows more about genetics than I do.

The basic idea is that three thousand years before the start of the story, there was a single man with a genetic mutation. This man managed the leader of a religion based solely on making sure that as many people as possible had the aforementioned mutation. However, with the allele being recessive and there being no method of testing people actually have the proper genotype, the religion engaged in eugenics with the leader having children with as many women as possible and then ensuring that the allele is passed on without excessive amounts of incest.

Now while this religion will be the dominant one for around a millennia, it should grow smaller and smaller over time until it's for the most part forgotten by the start of the story.

With all that, how likely would it be that a single character would have a pair of that specific recessive allele after three thousand years? I don't seem to have a sence of scale on this issue, but to a layman like me it sounds unlikely at best.

If my rambling doesn't make any sense, I'll do my best to clarify things.

Surprisingly, I actually get it. :P

I think there are ways to make it work, but it does depend on just how many people had this mutation in the first place. Remember, evolution does not work like Evolutionary Levels, so you won't suddenly get hundreds of people with this mutation turning up at the same time so a guy can start his religion. Mutations are usually very slow and not technically noticeable.

But - I think it's possible for a recessive gene to last 3000~ or so years, mainly because when a recessive gene meets a dominant one, it doesn't simply disappear forever. If the hero's parents, for example, both carried the trait partially without knowing it, then their child could end up expressing the gene. ......Though I might be wrong. So long since I took genetics.

Consider this: There have been cases when two Caucasian parents have given birth to a child of a different racial background - it's really rare, but sometimes both parents have the genes already there in their ancestry, and they don't even know.

I have no idea if that helps :S

I hope you enjoy whatever is written above. If not - well, I'm afraid that's life.

Indeed, that's why there's only one guy who has that mutation. Basically the guy starts his religion because his mutation is an immunity to something dangerous, so he's trying to pass the mutation to future generations so they can be protected from it.

Yeah, that's what I was thinking as well.

Huh, that's interesting.

Thanks for your comments, I'm glad to hear that the idea makes sense to someone else.

Boredknight sounds pretty accurate. I just went through biology, and we did a little studying of genetics. While your situation is unlikely, it's not impossible, and the Theory of Narrative Causality - things happen because the plot says they should - is your best friend in this case.

A recessive gene will only disappear if all of the people who carry it (not express it, carry it) die. Very few of those who carry it will express it.

...if you don’t love you’re dead, and if you do, they’ll kill you for it.

What would really break suspension of disbelief is if he was the only one in a very long time with this trait expressed. It should be present at a low rate all along. Say, 1 out of 10,000 people, or something like that.

If I'm asking for advice on a story idea, don't tell me it can't be done.

This. Maybe the guy gathered all the people he could find (perhaps not very many), then organized his little eugenics program.

[DATA EXPUNGED] - I would NEVER do that to a kitten! -Dr. █████

Another way to ensure that the gene gets passed is to have the religion be passed down in secret through a very narrow line of carriers, so that the trait is "guarded". If the baby born with the trait active needs to be a surprise, the secret group could fade away a few hundred years before the baby is born.

Doodles

What is the mutation?

Life's Gonna Suck When You Grow Up... But Is It That Great Now?... Also I'm Skylark2 now.

Apparently, some sort of poison/disease immunity.

What's precedent ever done for us?

It is possible, yes, but since the gene is recessive what would usually happen is that it would go bust (i.e. not appearing) without copious amount of inbreeding...

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Follow-up question: how bad would the inbreeding have to be? My quick calculation is that with a single shared parent, the first generation after that would have to consist of half-siblings, the generation after that of first cousins and so on. Any flaws in that logic?

AFAIK inbreeding doesn't exactly has to be bad. It just has to be there, since, you know, too bad inbreeding leads to the emergence of such recessive genes as mental retardation (for want of a better word), infertility, and other crippling symptoms that makes existing, let alone further reproduction, difficult.

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You know, this setup kind of reminds me of the plan of the Big Bad in Fire Emblem: Geneology of the Holy War. Use inbreeding to create a person with the right genetic makeup for their religious purposes.

Belief or disbelief rests with you.

I think that case is more about magic than science though.

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{Hooray! My reply didn't fail logic forever}

There might be a way to do it without near-constant inbreeding, but it's a real gamble. You say there's one guy who expressed it, right? Well, He might have to marry a woman who also expressed it, or at least a woman who carried it (in which case 50% of their kids would express it, and some others would carry it without expressing it). If he married a woman without the gene at all, then he's already narrowing his chances of making this recessive gene prevalent, because their kids would never express it, and rarely carry it.

But regardless, as long as all of the future offspring keep managing to have at least one carrier child, then it's plausible, and 100% in-breeding free!...

...Until you work your way back to the main character. His parents might have to be some degree of cousins, probably without knowing it. But they could be such distant cousins that it isn't even technically inbreeding.

phew. What I'm saying here is, it's all a very slim chance, but it works. I'll even say it works well; I like the idea.

I hope you enjoy whatever is written above. If not - well, I'm afraid that's life.

Each of us carries about 5 or 6 nasty recessive traits, on average. A full sibling will probably share about half of those with you, though that varies. With each recessive trait shared by both parents, the child has a 25% chance of showing it. So assuming you two carry 3 shared recessive traits, the kid has a 58% chance of at least one of those traits expressing.

If I'm asking for advice on a story idea, don't tell me it can't be done.

^ And more than 5 or 6 not-nasty recessives.

...if you don’t love you’re dead, and if you do, they’ll kill you for it.

Well this is high school biology so I thikn i can answer the question.

The short answer is: very plausible.

I think you are confusing "expression" with whether a gene is actually there are not. A recessive gene only means that it is less likely to be seen because dominant genes will be expressed instead. It does not in any way affect the presence or hereditary transfer of the recessive gene.

If nothing special happens (population pressure) genetic mutations don't go away if they have no negative consequences that seriously affect viability (ie. the ability to reproduce). The only danger is that very few people have the mutation, thus it could accidentally get wiped out by say... a random war, or at the very beginning some kind of house fire. But you say it is backed by a major religion that has the guy breeding like crazy. That's going to give you a super high chance of the gene being passed on and on. This would be similar to how there's millions of people related to ghenghis khan.

Ways to make the gene present, but very unlikely.

- Sex link it. Male calico cats are immensely rare. - Have the gist of genetic drift against it. - Have it inactive, but turned on by an environmental factor. - Have the gene also be a lethal allele i.e. those who exhibit the gene die from it. This could occur at any life stage. - Have the gene confined to a certain deme. etc.