Which mechanism keeps harmful alleles present in the gene pool?

Inbreeding is a mechanism that can keep harmful alleles present in the gene pool by increasing the likelihood of individuals breeding with close relatives. This practice reduces genetic diversity, leading to a higher probability that recessive alleles, which may be harmful, are expressed in the offspring. When closely-related organisms mate, there is a greater chance that both parents carry the same harmful allele, which can result in homozygosity for these traits. Such homozygosity can increase the prevalence of genetic disorders and decrease the overall fitness of the population by perpetuating these deleterious alleles.

In contrast, gene flow introduces new alleles into a population, natural selection typically removes harmful alleles from the gene pool, and mutations can add new variations, including potentially harmful ones, but they do not alone maintain the presence of these alleles in the gene pool. This understanding clarifies how inbreeding specifically contributes to the retention of harmful alleles within a population’s genetic makeup.