Eli5: Why does inbreeding cause genetic malformations?
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Many “bad” genes are recessive genes, so long as you are only carrying one of the genes the recessive trait isn’t expressed so you are healthy, but if you breed with another person who is also carrying the same recessive gene there is a likelihood of some of your offspring getting two copies of the recessive gene and the “bad” gene being expressed, breeding with close relatives increases the risk of you both carrying the same recessive gene. https://youtu.be/GTqXdraHe3E
A lot of genetic defects are recessive, so all you need is one of your parents to not have it, and you’re ok. If your parents are also siblings, that recessive gene gets passed on.
Take hair for example. The strength, density, and longevity of your hair is carried on the X gene. Men get 1 of them. Women get 2. As a result, men’s hair suffers in middle/old age which we call “male pattern baldness.” Women get two chances at good hair. Men get one.
Good genes can cover for bad ones.
Every generation you get new genes, and the good ones cover for the bad ones.
But if all you’ve got is bad genes, there’s no good gene to pick up the slack, and you start seeing the bad genes express themselves.
Just like you could have someone *carrying* genes for blue eyes while *expressing* the brown eye genes you got from your other parent, you’re *carrying* a bunch of shitty genes and *expressing* the good ones.
You and your siblings are *carrying* *THE SAME SHITTY GENES* while expressing healthy ones. If you breed, there’s a 25% chance your child gets SHIT from both sides with no healthy gene to fall back on, so while you’re *carrying* it, your child will *express it.*
Because mistakes happen. If you have mutations in your genetic code, they mostly cancel each other out (recessive genes). If you inbreed, you increase the odds of these mutations spreading, which increases the likelihood of genetic diseases
In the spirit of ELI5: Inbreeding does not ***cause*** genetic malformations. It only increases the chances of having one. As an example, brother and sister have the same recessive genes, when they procreate those recessive genes are more likely to become active than if it was two people from different familial origin.
There is a lot more to this, but again, it’s simplified for ELI5
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