Selection against homozygous recessive genotype

3,257 views · Published 16 June 2014 · 17:11 · Indexed 21 September 2026

Channel: Nikolay's Genetics Lessons · 2014 · Education

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Why Harmful Alleles Persist
In the last tutorial, we saw how natural selection, by acting on favorable or unfavorable phenotypes, can shift allele frequencies in populations. It’s reasonable to think that because they produce phenotypes that make individuals less fit, harmful alleles should disappear from any gene pool. But that tends not to be the case. Because harmful alleles are often recessive alleles, they can persist in a population almost indefinitely. And, even harmful dominant alleles, despite selection against the phenotypes they produce, can also often continue to persist in gene pools.

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