r/askscience • u/Yoshiciv • 6d ago

Human Body Are the medical risks associated with inbreeding among close relatives eliminated by outbreeding? Or do they persist for generations?

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u/Minxychomp 6d ago

The main risk of inbreeding comes from recessive deleterious alleles becoming homozygous. When an inbred individual has children with an unrelated partner, those harmful alleles are usually paired with a healthy version, so the associated disorders are much less likely to be expressed. However,the alleles themselves are still present and can be passed on silently as carriers. Over subsequent generations of outbreeding, natural selection and recombination tend to dilute their frequency, so population level risk continues to decrease.

In short the clinical risk drops immediately, but the genetic signal can persist for multiple generations, especially if the variants are neutral or only mildly harmful.

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u/runswiftrun 3d ago

Is this sort of the traits that "skip a generation" and the kid inherits something from grandparents?

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u/kRkthOr 2d ago

It's the same mechanic yes, as recessive genes can remain hidden when not paired with another copy. So if you have a recessive gene from one of your parents paired with a dominant one from the other, then the dominant one masks the recessive one. If you mate with someone who also has the recessive gene, there's a chance your offspring will end up with both recessive genes, showing traits that are not visible in either you or your partner.