I did some research to determine just how messed-up a child born of two people of exactly identical DNA (that is, a person and their clone).
The answer is, surprisingly, not very much. Yes, the kid would almost certainly have one or more genetic diseases (cystic fibrosis, for example), but only if the parent was a carrier for those diseases in the first place. It wouldn't be a total trainwreck like many (including me) imagined it'd be.
I did some research to determine just how messed-up a child born of two people of exactly identical DNA (that is, a person and their clone).
The answer is, surprisingly, not very much. Yes, the kid would almost certainly have one or more genetic diseases (cystic fibrosis, for example), but only if the parent was a carrier for those diseases in the first place. It wouldn't be a total trainwreck like many (including me) imagined it'd be.
The problem with that conclusion is that you're presuming the number of people who have some sort of potentially problematic genetic material are small, but nearly everyone has some. In fact, this is THE reason that inbreeding is dangerous to start with. (And self-fertilization is actually TWICE as bad as brother-sister incest on the inbreeding coefficient, since you only share roughly half your DNA with a sibling.)
Let's take a well-known example of sickle cell anemia, for example. Using the typical Punnett Square setup of having SS be totally normal blood, Ss being a carrier of one sickle cell gene, and ss being a carrier of two sickle cell genes, then only the person with ss genes actually displays sickle cell anemia. By contrast, the Ss person may carry sickle cell genes, but not only doesn't suffer from sickle cell anemia, but actually gets a benefit in the form of resistance to malaria, which is why genetic material that can cause a serious disease was actually naturally selected to perpetuate instead of go extinct.
Even in populations where sickle cell is relatively common, only about 10% of the population carries it, so it's still a relatively small percentage of the population that actually falls victim to sickle cell. In the case of self-fertilization (instead of a direct cloning), a Ss carrier of sickle cell genes, however, has a 25% chance of producing sickle cell anemic offspring.
And that comes to the big problematic assumption you're making - that most people don't have any genes that can carry genetic diseases... which is just plain wrong, most people carry several different potential genetic diseases, because there are tons of different things like sickle cell just waiting to give people Hapsburg Jaws. It's just that keeping genetic diversity flowing by not intermarrying prevents most of these because every ethnicity has their own distinct set of potential genetic problems.
The problem with that conclusion is that you're presuming the number of people who have some sort of potentially problematic genetic material are small, but nearly everyone has some. In fact, this is THE reason that inbreeding is dangerous to start with. (And self-fertilization is actually TWICE as bad as brother-sister incest on the inbreeding coefficient, since you only share roughly half your DNA with a sibling.)
Let's take a well-known example of sickle cell anemia, for example. Using the typical Punnett Square setup of having SS be totally normal blood, Ss being a carrier of one sickle cell gene, and ss being a carrier of two sickle cell genes, then only the person with ss genes actually displays sickle cell anemia. By contrast, the Ss person may carry sickle cell genes, but not only doesn't suffer from sickle cell anemia, but actually gets a benefit in the form of resistance to malaria, which is why genetic material that can cause a serious disease was actually naturally selected to perpetuate instead of go extinct.
Even in populations where sickle cell is relatively common, only about 10% of the population carries it, so it's still a relatively small percentage of the population that actually falls victim to sickle cell. In the case of self-fertilization (instead of a direct cloning), a Ss carrier of sickle cell genes, however, has a 25% chance of producing sickle cell anemic offspring.
And that comes to the big problematic assumption you're making - that most people don't have any genes that can carry genetic diseases... which is just plain wrong, most people carry several different potential genetic diseases, because there are tons of different things like sickle cell just waiting to give people Hapsburg Jaws. It's just that keeping genetic diversity flowing by not intermarrying prevents most of these because every ethnicity has their own distinct set of potential genetic problems.
Prtty much everyone has alleles that can cause disease. There seems to also be lot of people who *should* display a disease phenotype based on gentypic analysis, but they don't. Last time I looked at a paper on this (the team was looking at a bunch of SNPs), it seems most people have 36 to 60 or so problematic recessive, disease inducing alleles. Even if you have both alleles only around 10% of people with that genotype (based on what the team was able to pick up on analysis) will actually have the syndrome or disease. So it's not as bad as most would make this issue out to be. Epigenetics and the like make this all very complex to say the least.