Overdominance can also be described as heterozygote advantage, wherein heterozygous individuals have a higher fitness than homozygous individuals. An example in humans is that of the sickle cell anemia. This condition is determined by a single polymorphism.
Several kinds of selection can act to maintain genetic variation. One is overdominance, the situation in which heterozygotes have highest fitness. Other kinds are negative frequency dependence, multiple niche polymorphism, and spatial variation in selection.
A well-known example of overdominance occurs in the alleles that code for sickle-cell anemia.
This situation, known as heterosis or overdominance, leads to the stable coexistence of both alleles in the population and hence contributes to the widespread genetic variation found in populations of most organisms.
Overdominance. Overdominance occurs when fitness of the heterozygote is superior to that of either homozygote. The result is that both alleles are maintained in the population at an equilibrium frequency ( , read "q hat", where q = 0) that maximizes fitness.
Overdominance hypothesis: The overdominance hypothesis states that an organism that descends from parents of different genetic backgrounds will have greater resistance to a broader spectrum of potential dangers.
Definition of overdominance : the condition wherein a heterozygote produces a phenotype more extreme or better adapted than that of the homozygote.
0:000:51OVERDOMINANCE IN SICKLE CELL TRAIT - YouTubeYouTubeStart of suggested clipEnd of suggested clipThose who possess the sickle cell trait may thus display a form of inheritance known as overMoreThose who possess the sickle cell trait may thus display a form of inheritance known as over dominance the heterozygotes have a phenotype which might be the most adaptive in this environment.
More genetic diversity was retained in areas of low recombination, suggesting that associative overdominance, driven by disfavoured homozygosity of recessive deleterious alleles, is responsible for the maintenance of genetic diversity in smaller populations.
The fact that fitness overdominant mutations were always the first step in independent adaptive walks supports the prediction that heterozygote advantage can arise as a common outcome of directional selection in diploids and demonstrates that overdominance of de novo adaptive mutations in diploids is not rare.
A heterozygote advantage describes the case in which the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype. The specific case of heterozygote advantage due to a single locus is known as overdominance.
Simply stated, there is no common cause of stabilizing selection, besides the fact that the most average individual is selected for. In that way, like all forms of selection, the cause of stabilizing selection is the increased fitness and reproductive success that the median individuals have.