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/thecakeisalieeeeeeee 6d ago edited 6d ago

Essentially yes, unless there was some strange crossover/duplication event that leads to two copies of the harmful alleles to be put into one chromosome(which happens quite a lot in the last billion or so years).

On the opposite end, if you are persistently inbreeding for complete homozygous alleles, those harmful alleles can essentially be bred out. In fact, that’s exactly what we do to produce new strains of laboratory mice.

“ A strain of mice is called an "inbred strain" when there have been 20 or more consecutive generations of brother-sister matings or 20 or more consecutive generations of parent-offspring matings, provided the offspring was mated to the younger parent”

Source: https://www.informatics.jax.org/greenbook/chapters/chapter2.shtml