I have two questions (to start with). First of all, if a human is the product of incest between, say, a girl and her biological father, is there likely to be any kind of birth defects or chromosone funkiness? And, is it even possible at this point to know? Children being the product of incest is prolly one of those big time family secrets, so I don’t know if there’s even been enough reported cases to do any kind of studies.
Second, if a person suspects he or she might be the product of incest, is there any way to find out (like DNA testing) if both the mother’s father and the man the child was raised to believe was the bio-dad are both dead, so there’s no way to get DNA from the two men?
Oh, and one more question…if a person is in this situation (suspects he or she might be a POI), is there any reason to try to find out? I wonder what good it might do.
It’s always a good idea to know who your parents are. Anyone can have heriditary genetic predispositions. In cases of Incest, the odds increase significantly if there is a normally recessive genetic condition in the family.
A geneticist should be able to see a incestuous pattern with just the patients DNA and the mother’s DNA. Depending on the disposition of the bodies, DNA may still be obtainable. Other descendants of the suspected fathers will contain enough similarities to be fairly conclusive in a limited possibility search.
It is much more likely for problems to crop up in a product of incest than in nonincestuous matings. The reasons for this are clear. Each of us carries a certain number of defects on one of our parental chromosomes that is compensated for by our other parental chromosome. Because these defects are rare, it’s almost impossible for someone to inherit two identical defects from their parents if the parents aren’t related. However, if they are related, the chances of both parents carrying the same defects are much much higher, so it’s much more likely for the child to get two bad copies of a gene and have an associated problem.
There’s no need to study this in humans, firstly because the underlying mechansim is so simple, and secondly because it’s been studied extensively in other animals. And thirdly because there’s been enough incest in the human population that it has been easily checked and confirmed that yes, it works the same way for us. Royal families are notoriously good examples.
Thanks, y’all, for your answers, especially for expressing the information in plain English. Much of the research I tried before posting was pretty academic and therefore a little difficult for me to grasp.
Sometimes, discoveries in science tell us we don’t know as much as we thought. The monk Mendel pioneered the science of genetics by cross breeding vegetable plants. When I was a kid, we thought we could use Mendel’s principles to predict the eye color and hair color of a child of a given pair of parents. It’s safe to say the hair and eyes of some children caused innocent mothers to be accused of adultery.
Today, we know that human genetics are much trickier than Mendel’s charts. We all carry a lot of inactive genetic material. The chances of them popping up in our children are not so predictable.
What I’m getting at is that children born of incest are not all genetic time bombs. Many of them are perfectly healthy. Ten years from now, we might find out that part of this post is wrong.
There’s no reason to think eye and hair color don’t follow Mendelian genetics; it’s just that they’re affected by more than one gene, so Mendelian genetics gets pretty complicated.
Even with classic Mendelian genetics, not all children of incest are ‘genetic time bombs’. They have a higher chance than children of unrelated parents of having genetic problems, but that’s just a higher chance, not a death sentence. And by the way if the child of incest doesn’t manifest any genetic problems, then their children (assuming the other parent is unrelated) have no greater chance than anyone else of having genetic problems.
Getting to personal opinion, I’d say that the emotional issues involved in testing whether you’re a product of incest are way, way more important than the small potential medical benefits. If, emotionally, it’s better to let sleeping dogs lie, then don’t wake them up just for medical reasons.
The chance an otherwise healthy POI would have some kind of “chromosome funkiness” discovered by genetic testing, or be at increased risk of passing along said funkiness is trivially small. While inbreeding can promote the phenotypic appearance of otherwise recessive negative trait when its practiced over generations within a small population, any given genetic combination is a crapshoot. A POI you describe has a very very small chance of being anything but genetically typical for the population from which she is derived.
As to whether or not one should try to find out: From a medical perspective, my answer is “no” if the individual is otherwise healthy, and “no” if any health issues are able to be handled without knowing the genotype of the parents (breast cancer screening, e.g.) It would be the same answer from a social perspective, but that’s an opinion, of course.
It doesn’t add much value to be able to say, for example, “You might be at increased risk for polycystic kidney disease” unless there is something that can be done about diminishing that risk…
From a purely genetic standpoint, I’d bet on the product of an otherwise robust gene pool over the crapshoot of hybrid vigor even if the two parents were closely related.
And testing for it doesn’t require testing for parenthood. If you have a “bad pair of identical genes,” medically speaking it doesn’t matter whether one of your parents inherited a copy from the other one or the two copies reached your through two lines distant enough to be considered unrelated. Also, genetic problems can be linked to things like one bad copy and an inactive copy which aren’t identical, but neither one works well… in this case, there wouldn’t even be a so-many-thousands-of-years-before common ancestor.
OK, this seems like enough information to make a decision.
The child (possible POI) in my scenario wouldn’t benefit in any practical sense from finding out (it seems to me, based on what I’ve learned here). The child in question doesn’t have anything emotion invested in the answer, anyway, but she does have…
This is stupid and too complicated, and none of y’all know me IRL anyway, so…
I don’t have anything emotionally invested in the answer. I kinda feel a mild curiosity, but that’s it. My poor Mom, on the other hand, would be really upset if she knew I was even wondering about it, so I don’t want to do anything to make her feel bad.
The only reason I’ve given this some thought lately is because of my own medical issues. I was diagnosed two years ago with multiple sclerosis, and now I’ve been referred to a rheumatologist because it’s looking like I may be developing rheumatoid arthritis. I have other issues as well. And, whenever I fill out family medical histories, I make a note that my “biological father” left before I was born, and I don’t know much about his family. But the truth is, I don’t know whether that man was my bio-dad or if it was my Mom’s dad.
It sounds like there is no practical value in trying to find out, so finding out would just complicate things, and put me in a situation where I know something I don’t want my Mom to know. I don’t see any good in that.
Hmm. I guess the important question is what benefit you’d get from knowing it was true - if it were, of course. All you’d know is that you’re at greater risk for any genetic diseases that run in the family, but would you even know which ones you’d want to be tested for? And would knowing ahead of time what your genes are like make your life better or worse? Those aren’t easy questions, even leaving aside the psychological and family issues.
The only other thing I can think of that may be bothering you is the worry about passing things on to your own children, but as long as you don’t have a baby with a close relative yourself, they should be fine.
And for what it’s worth, IIRC, MS and RA share some common underlying issues - autoimmunity and inflammation, I think, so it’s not all that bizarre to come down with both - it may not be strange enough to cause one to look for strange genetic backgrounds. I would defer to a real doctor’s opinion on that, but that’s my impression right now.