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Omegaverse Genetics

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A Brief Primer on Genetics in Our World

Our DNA is made up of 23 chromosomal pairs. One pair is meant specifically to determine the sex of the child (male or female). XX means you’re female, XY means you’re male. When a new life is formed, the baby takes one chromosome from the mother and one from the father:

XX + XY = XX or XY (male or female)

That’s why the father determines the sex of the baby – they can either contribute the X chromosome (making the baby a girl) or the Y chromosome (making the baby a boy).

(Now remember Henry VIII of England. Ah, irony.)

This is true for humans – other species, such as insects or fish, have other ways of determining sex, and in some cases, there’s no Y chromosome at all, or there’s a “tick” on one of the X chromosomes that allows for fertility or infertility.

I’m assuming you’re reading this because you’re already familiar with the concept of the Omegaverse, which is basically a fandom excuse to get men pregnant. (Also, porn, but everything is an excuse for porn in fandom.) Which means you’re probably wondering right about now: “That’s lovely, Az, but if men carry the XY chromosomes, and two men can have a baby together, that means there’s a chance the kid could be a YY, right?”

Well, yes. That’s true. We can interpret that one of two ways:

YY = also equals male

YY = genetic anomaly that would result in a miscarriage

Personally, I like the second theory. It’s not that I want to wish a miscarriage on anyone. It’s that considering the shit writers have already put these characters through, miscarriages aren’t outside the realm of possibility. (John Watson is injured, suicidal, suffering from PTSD, and depressed, and that’s just canon. In fanon, he’s been impregnated, turned into a werewolf, turned into a were-dinosaur, murdered, turned into a vampire’s thrall, enslaved, regressed to a caveman, turned into a raven, fallen in love with a robot, shot up with heroin and cocaine, was a victim of child abuse, has a serial killer obsessed with him….and there’s at least one fic in which he’s already had a miscarriage.)

In the Omegaverse, it’s possible that a “tick” determines whether a child is an Alpha, Omega, or Beta. But I think this would end up being far more complicated than actually necessary for the sake of discussion. Also, I’m doing this as a happy-procrastination-exercise, and I can’t for the life of me make heads or tails of the relevant Wikipedia articles, so I’ll let someone who (a) is actually trained in genetics and (b) interested in Omegaverse write that particular explanation.

Omegaverse and Chromosomes

I’m going with the theory that in the Omegaverse, there are two sets of chromosomes which determine the sex of the baby. The X and Y chromosomes for male and female would work in the same way as in our own world. It’s just that they don’t determine fertility – in Omegaverse, the X and Y chromosomes determine only the outward appearance of the child. It’s another pair of chromosomes that affects fertility – the Alpha/Omega/Beta set of chromosomes.

There’s two ways to look at this particular set of chromosomes. There’s one in which there are two factors: Alpha (A) and Omega (O), and it’s a particular combination of those that determine if the child is Alpha, Omega, or Beta. There’s also one in which there are three factors: Alpha (A), Omega (O), and Beta (B). Let’s look at them both.

(Something to remember: for the purposes of this conversation, I’m going to go with the overall theory within Omegaverse that Alpha/Alpha pairings and Omega/Omega pairings are not conducive to procreation. Your personal Omegaverse rules may differ, of course, and if there’s interest and I’m still looking to procrastinate, I might make an addendum that covers that.)

The Two Chromosome Model

Let’s look what happens if there are only two chromosomes that determine fertility:

Omegaverse with Two Chromosomes

So what we see happening here is that in every pairing, you are statistically more or just as likely to have a Beta child as you are any other presentation. In fact, the Alpha/Omega pairing is only ever going to produce Beta children, period. There is no pairing that doesn’t give at least a 50 percent chance of a Beta child – meaning that the chances are in this world, Betas are very, very common.

This is borne out by the percentages. In our world, there’s a 50-50 chance that a baby will be male or female. Obviously some families have more males or more females, because the 50-50 chance is true for every birth. But overall, the world’s population is almost an even split between men and women – for every 100 women, there are about 101 men. (And as with individual families, this number changes based on the country – in the United States, for instance, there are more women than men.)

We have to assume that the same is more or less true in the Omegaverse. This means that the percentage of possible outcomes is probably indicative of the percentage of the world’s population. According to the Two Chromosome model, 62% of the world’s population is going to be Beta.

This is a big deal, particularly when you consider that we are looking at a single generation. When you look at the generation after this – when there’s a smaller percentage of Omegas and Alphas to go around, it’ll be even worse. Half the children of the Betas will also be Betas. All of the children of the Alphas and Omegas will be Betas. The numbers of Alphas and Omegas will continue to dwindle until there are none of them left.

And that’s one of the two main issues with the Two Chromosome model. The first is that genetically, it’s pretty stupid. Here we have an entire sexual model where Alphas and Omegas are genetically compelled to procreate: but the actual act of procreation does nothing to further their own lines. (I kind of think of it like a horse and a donkey creating a mule: okay, sure, but what’s the point?)

The second issue is when you actually apply it to the mountain of stories that are out there. As authors, we want our Alpha/Omega pairs to be fruitful and multiply. (Or just have to have lots of sex. Some of us really do come and stay for the porn.) But of those of us who are staying for the mpreg, I’m willing to bet we don’t want our Alpha and Omega pairs to have Beta children – unless we have a specific need for that in the story, or we want to ensure that Betas are the majority, and make a comment on the particular trope.

(Another possibility is if the writer wants Betas to be infertile full stop – but that also severely limits the possibility of children in the world itself. As in, makes it impossible, since the only way you can get an Alpha or an Omega is with a Beta in the first place, and if you make the Betas infertile…well, there goes the universe.)

Therefore, I think it’s much more likely that the Omegaverse would have three chromosomes. Also, more fun. Let’s look at why.

Three Chromosomes


Alpha (A)
Omega (O)
Beta (B)

Even with three chromosomes, the way genes are constructed, there’s always a pair of two chromosomes. The three possible chromosomes would thus go as follows:

AA, AB – Alpha
OO, OB - Omega
AO, BB – Beta

My theory is that the Alpha and Omega chromosomes are the dominant ones – when paired with the Beta (B) chromosome, they’re going to dictate the eventual outcome. But because they’re both dominant, when paired together, they cancel each other out – so AO results in a Beta child the same as BB. I think this is the only way that makes sense. If the B chromosome is dominant, then it has different implications which align themselves more toward the original two-chromosome world, in that an Alpha/Omega pairing is ONLY ever going to produce Beta (AO) children.

There’s quite a few fics out there where infertility among Betas is rampant – perhaps this would be part of the cause, that either the BB or the AO individuals are infertile.

Anyway, continuing with the actual Three Chromosome concept, let’s look at the way the various parings would work. It’s a bit more complicated than the Two Chromosome theory:

Alpha-Omega Pairings

Here we find again – in every combination, there’s at least a 50% chance that the child is going to be a Beta. The only difference is that we’re looking at only one pairing – the Alphas and Omegas, who in a two-chromosome model were only going to produce Betas. Now they can produce Alphas and Omegas as well – in fact, the Alpha/Omega pairing looks remarkably the same as the Two-Chromosome overall system, at least in terms of outcome.

You can also see exactly how important that Beta factor becomes: when both of the parents carry the B gene, it means they’re statistically more likely to produce both Alphas and Omegas – without that crucial neutral B, they’re only ever going to produce Alphas or Omegas.

(It’s a bit like how I remember right- v. left-hand dominance is determined – RR or Rr means you’re right-handed, rr means you’re left-handed. If you have one left-handed parent (as I do, actually), it means you carry at least one left-handed (r) chromosome. Assuming my mate also carried a single r chromosome, we’d have a 25% chance of having a left-handed child. How ambidexterity and multi-handedness works into this equation, I have NO idea. And if we were to apply this model to the Omegaverse…well, that’s another chapter which I might do depending on how badly I want to continue procrastinating.) MOVING ON.

Alpha-Beta Pairings

Okay, so picture me running around screaming right now. Can this be the geneticist’s version of an OMG moment? Because here, finally, is a model in which Betas are NOT necessarily the majority. In fact, there’s one pairing that results in nothing but Alphas, which I’m pretty sure some of you were going to despair about ever actually happening, and thinking of all the Doomsday fics with dwindling numbers and Omega Breeding Camps and the like.

(Hey, nothing wrong with a good Omega Breeding Camp fic. Bring it on.)

Basically, this just proves that the neutral B chromosome is seriously important to the continuation of the Alpha and Omega lines. If you wondered why Betas are important – they’re vital. And what’s more, Alphas and Omegas pairing with Betas actually increases the chances that the world will have more Alphas and Omegas.

Yes, Omegas too – because the Omega/Beta combination is of course the same as the Alpha/Beta combination – just with an increased number of Omegas instead of Alphas.

What this is means is all those fics that talk about how the Holmes line is predominantly Alpha (or Omega)? Totally probable…as long as they keep mating with Betas.

You can kind of excuse humans for not realizing until gene sequencing came around that the men were the ones who determined the sex of the baby – after all, XX + XY is a pretty straight-forward equation, and no matter what, the sex is always going to be a 50-50 of getting a boy or a girl. Within the Omegaverse, however, I have to think that after a while, someone would look at the various combinations of pairs and realize that certain pairings were going to result in certain outcomes. Sometimes Alphas and Betas have only Alphas. Sometimes they have both Alphas and Betas. Sometimes they have all three. But it would be rare for an Alpha and a Beta to have only Omegas, or only Betas. (Possible, yes. That’s because, despite these percentages, every time an Alpha and a Beta mate, the probability of having an Alpha/Beta/Omega child revert to the standard.)

(This actually makes a somewhat reasonable argument for scientists in the Omegaverse to look at genetics a bit earlier than what we’ve had in our own world – after all, the ratio of men to women is just about right for us. But in the Omegaverse, it’d be somewhat screwy, and thus more of a concern. Why are some children Omegas and some children Betas and some children Alphas, and is there a way to increase the numbers of one and not the others? It veers kind of close to genetic manipulation, I know, but so does any study of genetics, I think.)

Omega-Beta Pairings

The last type of pairing is the Beta/Beta. Now, this pairing is different, because the rules of Omegaverse, almost without fail, are that Alpha/Alpha and Omega/Omega aren't compatible for reproduction. However, in most Omegaverse stories, Beta/Beta is at least somewhat compatible (let's remember, Betas are basically us). There’s an entire trope within the Omegaverse that has Beta couples experience some level of infertility – although that might be in comparison to Alpha/Omega couples, who are so fertile they get pregnant just by looking at each other, half the time. Heck, anyone would look infertile compared to that!

Assuming that the Betas are no more infertile than the majority of the regular human race, we get three possibilities for Beta/Beta pairings:

Beta-Beta Pairings

Now, this is interesting. In every other pairing, there’s always a very good chance that the baby is going to share the fertility of at least one parent. (There’s a couple of exceptions, but not great ones. Yet there’s one pairing of Betas in which there’s a 100% chance that the child is not going to be a Beta – they’re either an Alpha, or an Omega, and that’s it. No chance of Beta children.

Even so, a Beta/Beta pairing is still more likely to produce Beta children than Alphas or Omegas. The difference is that most of the Beta children from a Beta pairing (4 out of 6) are going to carry the neutral B chromosome, which means that if those children pair with either an Alpha or an Omega, they are always going to have Alpha or Omega children. Even a Beta child with the AO chromosomes are statistically more likely to have Alphas or Omegas than they are Betas when paired with an Alpha or Omega partner (a 50-50 percent chance).

Which means that of all the possible combinations - you actually really want a Beta involved in the process. Betas are key to the continuation of the human species. Without Betas, the world would probably not exist – or at least it’d be a lot smaller than it otherwise is.

Death, Taxes, Statistics If I thought was I getting over my head with genetics, now I’m really sunk. Here’s where I start playing with statistics.

In the classic XX/XY model, it’s always a 50-50 chance that the child will be male or female. This is mostly borne out in the real world, where the actual split between men and women is relatively close to 50-50. (There’s about 101 males for every 100 females, though that changes on the country.)

In the Omegaverse, the way I’ve structured the chromosomes, and the fact that the B chromosome is neutral but dominant, it results in Betas having a majority of the population – but only just. The fact that the scales aren’t even are also an issue – Alpha/Alpha pairings and Omega/Omega pairings are never going to produce children, which means the percentages are further skewed.

Remember in the Two-Chromosome model, those numbers were seriously wonky. Without a Beta chromosome to even the odds, the breakdown of Beta/Alpha/Omega was 62/19/19 – a long way from the ideal 50/25/25. But when we add the Beta chromosome back into the mix, something interesting happens:

Author's Note 2018: so... in re-uploading the images, I seem to have lost the original image that went here, and several years, I have NO idea what it was! If anyone downloaded it and can help me out, I would appreciate that. Thank you!

In a perfect world, the Omegaverse should be 50% Betas, 25% Alphas, 25% Omegas. And we actually get that perfect world with the Beta/Beta pairing. What’s more, we get very close to a 50/25/25 breakdown when we look at the overall numbers: 43% of all possible children born are likely to be Betas, with Alphas and Omegas at 28% each. The vast majority of any single group is going to be Beta – but as a whole, Alphas and Omegas are going to carry a serious amount of weight in the world.

(Which has some serious implications if you’re more into the political side of the Omegaverse.)

What This All Means

For doesn't mean the end of the world if you want Mummy and Father Holmes to be Alpha/Omega but Mycroft is an Alpha and Sherlock is an Omega. First of all, this is fanfiction, and this is my high school genetics interpretation of a world that doesn't exist. If there's one thing fanfic writers are good at it, it's ignoring logic and/or canon when it doesn't suit.

(As my husband says about Doctor Who, we're writing about an alien who travels in a blue police box through time and space. LOGIC very rarely enters into the equation.)

But for those of us who have wondered how the heck it works at a genetic level with the Omegas and the you go. Have fun with that.