Genetics of a human-animal hybrid

Question

It’s the age of genetic engineering, and Scientists, in league with shady corporations, have created a group of human-animal hybrids, hereafter referred to as Metamorphs.

Metamorphs are designed as slave labour; since they are nonhuman, human rights don’t apply to them. However, some buyers may wish to use their Metamorphs for breeding purposes, which leads to the risk of human-Metamorph hybrid children that could present serious legal backlash. For plot-related reasons, I don’t want the Metamorphs to be made infertile with humans, so I have devised a solution that means that Metamorphs produce only human children when paired with humans:

As any geneticist will tell you, there are dominant genes and recessive genes. The animal half of the metamorph genome has been made “hyper-recessive”, so that when paired with a human partner, the animal traits are not expressed in the offspring. The animal genes only express themselves when paired with another metamorph.

Is this a plausible solution from a scientific point of view, or no?

Answer 1

No. Also, you have a contradiction in your metamorphs

You said that Metamorphs don't have human rights because they don't count as human. But here lies a problem: by definition they ARE human if they can produce viable offsprings with them. From wiki:

A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction.

You have to understand that introducing serious changes would quickly result in non-viability of children when pairing with baseline humans. More or less ANY chromosomal changes would lead to infertility (in metamorphs-human pairs, metamorphs-metamorphs pairs could still be made fertile). And even if you keep the number, size and genetic makeup of chromosomes more or less the same, introducing too many changes to the genetic structure would lead to same issue. So your problem is that if the change is small enough for them to have viable offsprings with basaeline humans they would still count as humans, but if the changes are larger, they wouldn't be able to be bred with humans.

And even if relatively small changes (where you could have an issue telling metamorphs apart from humans) can introduce issues, so them having the ability to mate with humans would have to be made on purpose (and not easily). Which goes against your motion that those offsprings would face legal backlash. And required level of genetical modification for such a thing would be high enough that such society could create servant race without human parts (well, they could look human on the outside). Which would be far easier to sell to the population and lawmakers - but sadly, no viable metamorphs-human hybrids in that case. Not that that would stop certain people from engaging in sexual activities with metamorphs, social taboo or not, it just wouldn't produce offsprings.

Also, you have some misunderstanding of recesive/dominant genes. You have 2 (or multiple) copies of the SAME gene. And that same gene can have multiple variations, some of which can be called recesive and some dominant. But it is still the same gene, it encodes practically same protein with practically same function. So you generally can't have different functionality on your recesive genes (there are exceptions, as always in biology, but they are rather rare). Not to mention, most atributes are determined by quite a lot of genes that interact with each other, so that clear recesive/dominant divide is not all that common (Mendel was extremely lucky with his choice of atributes).

Answer 2

Simple Answer: No

There is no such thing as "hyper-recessive" genes. The nature of earth-based genetics are that there are two of each gene, one from each parent. If all "metamorph" versions of a given gene are recessive, then the offspring of a human and a metamorph will be a human, but their offspring will show metamorph traits if they mate with another human/metamorph offspring or a metamorph.

Put simply, math says that your plan doesn't work. If the genes are recessive ("hyper" or otherwise), then any Metamorph must be homozygous for every gene, and must pass those genes on to their offspring, setting the genes up for expression in the next generation.

Answer 3

Handwavy Answer : Yes

The Metamorph sex cells (MX=egg and MY=sperm) are a complete copy of DNA instead of only a single strand. Attached to this cell is a nanobot controller whose purpose is to maintain the 50/50 human-animal combination that has been found to be required for viable offspring.

When a MX combines with a MY, the accompanying nanobots link and begin the splitting and combination of the two cells to build the zygotes [1].

When a MX or MY combine with a human sex cell (Y or X, respectively), the nanobot has another function. When the human sex cell combines with the Metamorph cell, the lone nanobot still goes through the process of dividing the Metamorph cell, but it also filters the genes so that only a single strand of DNA remains, and that strand is made up of only 100% human DNA. The nanobot then expels itself and the excess junk DNA from the zygote, where normal bodily processes can dispose of them.

1: A side effect of this process is that two zygotes are produced (non-identical twin births being the rule for Metamorphs). If there are different types of Metamorphs (ie cat-people and dog-people) and two different types produce offspring together, then one of the children will be of one type and the other will be the other.

Answer 4

Very handwavy but yea sure, just have two coexisting genomes with some caveats (caveats listed in text)

This is stretching the boundaries or biology in reality But if there were, say, two sets of genomes (human, morph) in each metamorph's cells it might... be possible?

Think of it like this. Its not genes that directly determines what we are, its how those genes are expressed. if a beaver were to have human genes in every cell but no relevant proteins to express that, the beaver is still a beaver, maybe with some extra cellular detritus.

So if a metamorph's specialized double duty egg or sperm hits the egg or sperm of a human, the human genes match up and create a baby and the morph genes get disregarded and flushed out in the process. But if morph-morph action happens, both genomes are completed and expressed accordingly.

So the metamorph DNA kinda acts like custom game mod or API that redirects proteins to express the intended metamorph state.

A technicality is that the metamorph exclusive genes need to be more like a DLC to the human genes and takes priority i.e. overriding human traits that would normally be expressed with human only genes. in that way if only morph genes are paired, the resulting baby is a miscarriage and animals won't be born.

This is very shaky and handwavy but imo it could work. The reason why it uses human genes but acts like a dlc can also be explained by its background from shady corpos in that some scientists had created a viable metamorph "DNA DLC" but wanted to manufacture a lot of those metamorphs so they made it so that the DNA DLC would be passed on from metamorph to metamorph but not to humans as to "keep the genes clean" or prevent "normal" human populations from declining due to the inevitable flings.

Answer 5

As jdunlop has already explained in his answer, for a true Hybrid no, simply not how genetics work.

Howsoever.

If you drop the hybrid and go with some form of lab grown Chimaera instead then the answer could be a qualified yes.

As the cells making up the pertinent portion of the gonads or ovaries that produce sperm and eggs will be then either entirely human or entirely something else .. so your chimera will be able to mate successfully with the species corresponding to the genes of those cells and the offspring is going to be entirely of that one species.

Your chimera will be able to mate successfully with the species corresponding to those genes.

Well, at least with respect to sperm penetration of the egg cell and the beginning of cell division.

Physical ability to do so is another matter, depending on species one might be too large or small for the other to actively couple with it, and the 'equipment' might not be of compatible types of course.

Whether it feels any inclination to do so is of course yet another matter.

And womb environment can also be an issue when it comes to a developing embryo actually reaching term as the wrong species womb for the developing embryo may not (depending on species) provide a 'welcoming' environment for the developing embryo which will then die.

Things like body temperature and acidity of womb environment matter quite a lot and can vary considerably species to species.

But those are all issues that with careful choice of species used can be managed or avoided.

..

An alternative option is to surgically remove the gonads and ovaries of all your hybrids before sale and replace those parts with lab grown human ones of the buyers choice .. thus making them into chimera as well as hybrids of course.

Tissue rejection of the new gonads or ovaries can be avoided by 'inoculating' the hybrid against rejecting the chosen cell line for its new gonads or ovaries by simply injecting a small amount of cells from that cell line into it while in the womb before it's immune system 'calibrates' itself.

You'll find some link resources to help explain that 'inoculation' here.