Many human recessive genetic diseases are maintained despite continuing selection against them because

Question

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Heterozygotes have a higher fitness than either homozygote for some recessive genetic diseases because they have one functional allele and one nonfunctional allele, which provides some protection against the disease while still allowing the nonfunctional allele to be passed on to offspring. This maintains the recessive allele in the population, despite selection against homozygotes with two copies of the nonfunctional allele.

Many Human Recessive Genetic Diseases Are Maintained Despite Continuing Selection