Geneticist Dopers, help me work out how the mutant gene is inherited in Marvel comics

I debated on whether to put this here, in Cafe Society, or in GQ, and finally decided that MPSIMS was the safest bet.

I’d like to brainstorm some ideas on how mutancy (defined as a Marvel Comics mutant, not necessarily the same as a real-life mutant) is inherited in 616 MU. That is to say, the genetics of how the mutant gene is passed on. Now, I realize that obviously Stan and Jack knew squat about heredity when they first came up with the X-Men, so don’t just tell me “oh, it’s fictional, don’t worry about it.” Not only do I know that, I don’t care, and that attitude is no fun anyway.

My best friend is a horse person, and as she was explaining to me the complicated genetics of horse coloring, I blurted out, “Oh, I bet this is how mutant genes work in the MU!” See, I’m convinced that it’s not just the fabled X-gene, there must be at least three genes at work producing mutants, and possibly more. Here’s what we know:

Two humans can produce mutant children: Too many examples to list, but a notable example is the Guthrie family, which has produced both mutant and human children.

Two mutants can produce a human child: Probably the best example is Sabretooth and Mystique’s son, Graydon Creed.

A human and a mutant can produce mutant children: Plenty of examples, including Charles Xavier and Gabrielle Haller’s son Legion, Magneto and Magda’s children Wanda and Pietro, and Banshee and his wife Maeve’s daughter Siryn.

Two mutates can produce a mutant child: By mutates, I’m referring to people who gained superhuman powers accidentally, as opposed to naturally. A good example is Reed and Susan Richards of the Fantastic Four, and their very powerful mutant son Franklin.

I can’t at present recall a human and a mutant producing a human child, or a mutate/human or mutate/mutant pairing producing either a human or a mutant child, but there may well be examples of both I’m forgetting. There’s also a mutant/Inhuman pairing (Quicksilver and Crystal) that produced a human child (Luna), but Inhuman genetics are another thorny issue that’s probably too complicated to go into here. But as these examples clearly show, not only can humans, mutants, and mutates (and Inhumans) interbreed, but they can produce viable offspring who may be humans or mutants. Sadly, there aren’t many third generation examples to study, and the few there are tend to be too complicated to provide a clear picture of inheritance, such as Speed and Wiccan of the Young Avengers, who’s father may be a robot, Satan, some combination of the two, or they may have just been generated out of thin air by their mutant mother.

But what does this have to do with horses? Well, horses have two base genes that control coat color, e for the recessive red, and E for the dominant black. In addition, there’s also a whole pack of modifying genes that can change the expression of e and E. I think something similar is going on with mutancy, in that there’s not one, but several genes controlling whether someone is a mutant or not and how it’s inherited.

What I think is that there’s a gene, we’ll call it the superpower gene, or S for the hell of it, that codes for whatever superpowers someone has. However, it needs an activator gene to turn it on; this activator is probably the X-gene that is usually talked about in Marvel comics. In addition, there seems to be another gene that may code for the Secondary Mutations that some mutants develop, and possibly another gene or groups of genes that determine when a mutant power activates (most mutants develop their abilities at puberty or soon after, but some like Nightcrawler were born obviously mutant).

Perhaps many or even most humans carry a latent S gene, but without an X to activate it, never develop superhuman powers without a stimulus such as exposure to cosmic energy or genetic tinkering. Other humans carry an X but no S, and when paired with a Sx (S positive, X negative) mate can produce XS (mutant), Ss (human), or Xx (X positive, S negative, also human) children. However, the problem with this scenario is that two mutants (XS) couldn’t produce a Xx or Ss child, since both would be carrying a Superpower gene and a X-gene. Since we know from canon that two mutants CAN produce a human child, then obviously the genetics are more complicated than this.

So geneticist Dopers, do you think there’s some incomplete dominance genes in this scenario? Or possibly more than two genes necessary to produce a mutant child?

Couldn’t each power have a separate gene?

I was thinking about that, too. Sadly, our sample size of second-generation mutants is small, and third-generation mutants almost nonexistent. What we do know is that second-gens often have similar, but by no means identical, powers to their mutant parent, and occasionally they have completely different powers from *either *mutant parent.

Magneto’s extended alternate-reality clan offers a rare, but somewhat skewed, glimpse of three generations of mutants. Magneto himself controls electromagnetism; of his three surviving children, we have another magnetokinetic (Polaris), a speedster (Quicksilver), and an energy-wielder/reality-warper (Scarlet Witch). Complicating the issue is that not only do the twins and Lorna have different mothers, from whom they might have inherited any number of modifier genes, but also that Wanda was influenced while in the womb by the demon Chthon, modifying her original powers to give her control over magic. I think that Wanda’s ‘coded’ mutant powers would probably have made her a energy-wielder like her father and half-sister, perhaps a magnetokinetic, but because her modified powers have been with her since birth it’s impossible to tell.

Quicksilver’s daughter Luna is human, but because her mother Crystal is Inhuman, this adds a whole nother dimension to her genotype. Polaris has no children. Of Wanda’s children, the best example, ironically enough, may be her alternate-universe daughter with Nightcrawler, Nocturne. While Nocturne inherited the phenotype and many of the powers of her father, she can also fire hex bolts (apparently derived from her mother’s powers) and possesses unique abilities neither of her parents possess, such as body possession and low-level telepathy. As I said before, the unusual circumstances behind Speed and Wiccan’s births make it difficult to determine what’s going on with them genetically, but it’s worth noting that Billy can generate lightning bolts (possibly some sort of electromagnetic control unrelated to his magic spells) and that Tommy is a speedster and can vibrate the molecules in matter, causing any solid object he directs his vibrations at to explode.

Based on the info given here, I don’t think you can say squat about mechanism. You could, for example, have a single-gene system with incomplete penetrance.

Note that if there X and S are two separate genes, then unless they’re sex linked each individual would have two alleles of each. So if the population has only two possible alleles for each gene there would be 9 possible genotypes:

XX Ss *
XX ss
Xx SS *
Xx Ss *
Xx ss
xx SS
xx Ss
xx ss

If you assume that manifesting mutant powers requires one X and one S allele, then the four genotypes with asterisks would be “mutants”.

Plugging this model into breeding two “mutants”:
[li]The XX SS genotype would be guaranteed to have all-“mutant” offspring regardless of mate. [/li]
[li]XX Ss mated to XX SS or Xx SS would give all-“mutant” offspring; mated to another of the same or to Xx Ss they’d give 3/4 “mutant”.[/li]
[li] Similarly, Xx SS mated to XX SS or XX Ss would give all-“mutant” offspring; mated to another of the same or to Xx Ss they’d give 3/4 “mutant”.[/li]
[li]Xx Ss mated to another of the same would give 9/16 “mutant”.[/li][/ul]

Thus, many “mutant” x “mutant” matings could have “normal” children.

Why not just say it’s recessive, we got that. That’ll easily fulfill all 3 of your scenarios. The only problematic one is the 2 mutants producing a normal child.

But what if you made it like many of the disorders we have out there where it may have reduced penetrance.
Or you could have it that the genes can produce a certain… mutant protein perhaps, and it’s the AMOUNT of mutant proteins one has that can determine the type and severity of one’s mutation. Like how there are CGG repeats in Fragile X Syndrome that can add up over generations and if someone has enough of those repeats it can lead to them having the syndrome. That could explain how some people may have “Levels” of mutant powers, while others have latent to no powers.

And then if we added in your ideas where there’s an X activator gene and an S latent gene we could better modulate it. Ordinary people could have these “repeat sequences” in their DNA however it’d take an Activator protein to come along and perhaps trigger someone based on the number of repeats one has. We could also say that perhaps these genes are found not in DNA, but in PLASMIDS similar to Mitochondrial DNA or bacterial DNA, and that each plasmid could contain the different types of powers basically.

So when two mutants mix and match to produce offspring, the Plasmids from the Mother and from the Father are both transmitted to the Child with some chance for random mutations to occur. This will allow the POTENTIAL for the child to be a mutant. Then we could have your ideas of an X ACTIVATOR gene to actually come along and produce a protein complex that may be created to unleash the mutant powers that these plasmids could produce.

That way you have a way to show how mutants can produce other mutants or normal children, and how their powers can be similar or different, and you can also show how some mutants may be more or less powerful than other ones too.