We see in wildlife mules, ligers and tigons as example of genetic dead end offspring as their parents were genetically too distinct
At the same time offspring from genetically too similar parents : siblings cousins etc produces an offspring with bad genes
What is the goldilocks zone genetically that is considered just right? Is it the same or different among species?
In: 3
Probably, but nobody at this point would ever predict what it is, for any particular species.
In plants, [heterosis](https://en.wikipedia.org/wiki/Heterosis) or hybrid vigor is an extremely, extremely common phenomenon. It would be surprising if there weren’t some kind of equivalent that affected most species to some degree. Breeding programs essentially work by making a prediction “this is the sweet spot for the most genetically-robust offspring”, and then you breed plants to try and make that happen. And then you see how well it worked, and you keep on going from there in an iterative process that generates improvement.
And breeding programs work very well, but the problem is that there’s actually no way to just outright perfectly calculate an organism’s phenotype (observable traits) on the basis of its genotype (genetic sequence). You can calculate individual simple traits, but not, like, from first principles; those things only work for an organism you’ve already studied really, really well, and it doesn’t work for all possible traits. So since the models are imperfect, there’s still been room for continual improvement.
Besides: development is an ongoing process. Since it takes place over a lifetime, there are other factors involved in phenotype other than just the genotype. These factors are often described as “environmental”, things like nutrition… although note that your prenatal environment, impacted heavily by mom’s genes, will also impact your own development. That’s already very important for humans, but it’s even more important for plants since we are designing them to yield food, fiber, etc. under particular climatic conditions.
There isn’t a “goldilocks zone.” Speciation isn’t really well defined. A good example is ring species. I’m going to simplify the following but it’s the general idea. There are rabbits that live in Canada that can breed with the rabbits in the US. The US rabbits can breed with rabbits in Mexico. However the Canada rabbits and Mexico rabbits can’t breed.
Essentially the “sweet spot” is simply “does this pairing result in children who can have children.” It’s all our genes care about.
Probably, but nobody at this point would ever predict what it is, for any particular species.
In plants, [heterosis](https://en.wikipedia.org/wiki/Heterosis) or hybrid vigor is an extremely, extremely common phenomenon. It would be surprising if there weren’t some kind of equivalent that affected most species to some degree. Breeding programs essentially work by making a prediction “this is the sweet spot for the most genetically-robust offspring”, and then you breed plants to try and make that happen. And then you see how well it worked, and you keep on going from there in an iterative process that generates improvement.
And breeding programs work very well, but the problem is that there’s actually no way to just outright perfectly calculate an organism’s phenotype (observable traits) on the basis of its genotype (genetic sequence). You can calculate individual simple traits, but not, like, from first principles; those things only work for an organism you’ve already studied really, really well, and it doesn’t work for all possible traits. So since the models are imperfect, there’s still been room for continual improvement.
Besides: development is an ongoing process. Since it takes place over a lifetime, there are other factors involved in phenotype other than just the genotype. These factors are often described as “environmental”, things like nutrition… although note that your prenatal environment, impacted heavily by mom’s genes, will also impact your own development. That’s already very important for humans, but it’s even more important for plants since we are designing them to yield food, fiber, etc. under particular climatic conditions.
There isn’t a “goldilocks zone.” Speciation isn’t really well defined. A good example is ring species. I’m going to simplify the following but it’s the general idea. There are rabbits that live in Canada that can breed with the rabbits in the US. The US rabbits can breed with rabbits in Mexico. However the Canada rabbits and Mexico rabbits can’t breed.
Essentially the “sweet spot” is simply “does this pairing result in children who can have children.” It’s all our genes care about.
There isn’t a “goldilocks zone.” Speciation isn’t really well defined. A good example is ring species. I’m going to simplify the following but it’s the general idea. There are rabbits that live in Canada that can breed with the rabbits in the US. The US rabbits can breed with rabbits in Mexico. However the Canada rabbits and Mexico rabbits can’t breed.
Essentially the “sweet spot” is simply “does this pairing result in children who can have children.” It’s all our genes care about.
Probably, but nobody at this point would ever predict what it is, for any particular species.
In plants, [heterosis](https://en.wikipedia.org/wiki/Heterosis) or hybrid vigor is an extremely, extremely common phenomenon. It would be surprising if there weren’t some kind of equivalent that affected most species to some degree. Breeding programs essentially work by making a prediction “this is the sweet spot for the most genetically-robust offspring”, and then you breed plants to try and make that happen. And then you see how well it worked, and you keep on going from there in an iterative process that generates improvement.
And breeding programs work very well, but the problem is that there’s actually no way to just outright perfectly calculate an organism’s phenotype (observable traits) on the basis of its genotype (genetic sequence). You can calculate individual simple traits, but not, like, from first principles; those things only work for an organism you’ve already studied really, really well, and it doesn’t work for all possible traits. So since the models are imperfect, there’s still been room for continual improvement.
Besides: development is an ongoing process. Since it takes place over a lifetime, there are other factors involved in phenotype other than just the genotype. These factors are often described as “environmental”, things like nutrition… although note that your prenatal environment, impacted heavily by mom’s genes, will also impact your own development. That’s already very important for humans, but it’s even more important for plants since we are designing them to yield food, fiber, etc. under particular climatic conditions.
It depends on the organisms. For mammals it seems a few times removed is best because the rate of our protein production and developmental life cycle phases. For plants and some organisms they can impregnate themselves amd its fine because their genes don’t matter as much about how much proteins they produce… like a plant,it will just keep growing if it can maintain a proper balance of nutrients uptake…f it is making too many proteins due to a certain gene combination. Humans for example have a more complicated life and growth cycle which uses far more chemicals amd we aren’t allowed as much tolerance om our gene variation then say an insect is. We have a delicate chromosomal balance relative to other species. If a strawberry picks up a few more chromosomes accidentally it may grow better than before.
Reproduction is really the sweet spot though. If the liger is born infertile then that’s not good for its population. It mostly depends on just how similar the sexual reproduction portions of the genes are. If they are very very similar than the mechanisms of sex organs and reproduction can continue indefinitely but if they are too different the sex organs wo t produce the right amount of chemicals for the new animal and it likely will not ve able to reproduce itself or die like you mentioned.
It’s like taking an engine out of one car amd putting it into another, depending on the similarities of the entire system will determine the effectiveness of the new motor.
It depends on the organisms. For mammals it seems a few times removed is best because the rate of our protein production and developmental life cycle phases. For plants and some organisms they can impregnate themselves amd its fine because their genes don’t matter as much about how much proteins they produce… like a plant,it will just keep growing if it can maintain a proper balance of nutrients uptake…f it is making too many proteins due to a certain gene combination. Humans for example have a more complicated life and growth cycle which uses far more chemicals amd we aren’t allowed as much tolerance om our gene variation then say an insect is. We have a delicate chromosomal balance relative to other species. If a strawberry picks up a few more chromosomes accidentally it may grow better than before.
Reproduction is really the sweet spot though. If the liger is born infertile then that’s not good for its population. It mostly depends on just how similar the sexual reproduction portions of the genes are. If they are very very similar than the mechanisms of sex organs and reproduction can continue indefinitely but if they are too different the sex organs wo t produce the right amount of chemicals for the new animal and it likely will not ve able to reproduce itself or die like you mentioned.
It’s like taking an engine out of one car amd putting it into another, depending on the similarities of the entire system will determine the effectiveness of the new motor.
It depends on the organisms. For mammals it seems a few times removed is best because the rate of our protein production and developmental life cycle phases. For plants and some organisms they can impregnate themselves amd its fine because their genes don’t matter as much about how much proteins they produce… like a plant,it will just keep growing if it can maintain a proper balance of nutrients uptake…f it is making too many proteins due to a certain gene combination. Humans for example have a more complicated life and growth cycle which uses far more chemicals amd we aren’t allowed as much tolerance om our gene variation then say an insect is. We have a delicate chromosomal balance relative to other species. If a strawberry picks up a few more chromosomes accidentally it may grow better than before.
Reproduction is really the sweet spot though. If the liger is born infertile then that’s not good for its population. It mostly depends on just how similar the sexual reproduction portions of the genes are. If they are very very similar than the mechanisms of sex organs and reproduction can continue indefinitely but if they are too different the sex organs wo t produce the right amount of chemicals for the new animal and it likely will not ve able to reproduce itself or die like you mentioned.
It’s like taking an engine out of one car amd putting it into another, depending on the similarities of the entire system will determine the effectiveness of the new motor.
Genetic robustness depends on the environment and the environment changes over time. Darwin’s finches are a good example of this because they deliberately hybridize to survive as the climate shifts cyclically because of ENSO weather cycles (el nino/la nina). Hybrids are more common than people are aware of but they’re not always fit. A lot of animals in zoos aren’t releasable because we unintentionally hybrid bred them. Orangutans are one example where animals from different populations were bred together in zoos and their offspring had health and behavior issues that make them unfit for any repopulation programs for orangutans. Looking at humans, we have around 2% Neanderthal or Denisovan DNA, so only a little bit of hybridization was survivable.
“Hybrid vigor” is probably the genetic robustness you’re thinking of where the offspring of two different species is better than the parents. This isn’t something that’s guaranteed, you can get a bad mix up of genes just as you can get a good one. What scientists think happens in hybrid vigor is that one species contributes a better allele for a gene that winds up being dominant. To use an example gene, this would be like one species having only brown hair while another had only blond hair and when they have offspring, the brown hair gene is dominant to the blonde hair gene so all offspring have brown hair. In theory the brown hair species would have a number of dominant good genes and the blond haired species would have a number of different dominant good genes and when mixed you get an offspring with more good genes than either parent. The problem here is, when those offspring have their own children, the genes are shuffled again so you don’t necessarily wind up with grandchildren that are still robust, they’d only have some of the better genes their parents had. So you only get hybrid vigor once and then it gets diluted again. That’s because that blond gene is still there and available for offspring to inherit, it was just recessive in the first hybrid. Breeding hybrids to other hybrids, there’s a 25% chance of blond offspring.
In terms of inbreeding, what happens is something called Muller’s ratchet. Mutations occur at a predictable rate for each species depending on how quickly the animal breeds. Some of those mutations cause health issues. If we just cloned ourselves repeatedly those mutations would just build up over time until our clone offspring had too many mutations to survive. Genetic recombination through sexual reproduction helps get rid of those mutations because some of the other parent’s DNA gets swapped in for the mutant version so for any offspring with a bad copy, there are a few that have good copies. How much inbreeding any population can tolerate depends on generation timing and how quickly new mutations occur and how big the population is because that dilutes the bad mutation. So in a country with a high, international population like China, even siblings giving birth isn’t a big deal as long as it’s not happening repeatedly. But in a more limited population, like Iceland for instance, siblings having children is a bigger risk.
So the answer is that there’s no fixed spot for most genetically robust offspring. It depends on the environment, the species, and the population size.
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