What does underdominance mean in biology?
Underdominance is classically defined as the genetic condition where the fitness of heterozygote individuals is lower than the fitness of both of the parental homozygotes (Hartl and Clark 1989). There are two stable and one unstable equilibria in such a system with two alleles.
What is underdominance in evolution?
In genetics, underdominance (referred to in some texts as “negative overdominance”) is the opposite of overdominance. It is the selection against the heterozygote, causing disruptive selection and divergent genotypes.
How does underdominance affect allele frequency?
With underdominance, heterozygotes have lower fitness than both homozygotes. Underdominance does not preserve genetic variation, and one of the alleles will either be lost or spread to fixation, depending on its initial frequency.
What are the 5 Hardy-Weinberg assumptions?
The Hardy–Weinberg principle relies on a number of assumptions: (1) random mating (i.e, population structure is absent and matings occur in proportion to genotype frequencies), (2) the absence of natural selection, (3) a very large population size (i.e., genetic drift is negligible), (4) no gene flow or migration, (5) …
What causes underdominance?
Under natural conditions underdominance can be caused by chromosomal rearrangements [11]. These rearrangements can accumulate between closely related species [12], [13], despite an exceedingly small predicted probability of becoming established [14], [15].
Does overdominance maintain genetic variation?
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.
What is underdominance selection?
Underdominance refers to natural selection against individuals with a heterozygous genotype. Here, we analyze a single-locus underdominant system of two large local populations that exchange individuals at a certain migration rate. The system can be characterized by fixed points in the joint allele frequency space.
What are the five conditions necessary to maintain genetic equilibrium?
The conditions to maintain the Hardy-Weinberg equilibrium are: no mutation, no gene flow, large population size, random mating, and no natural selection. The Hardy-Weinberg equilibrium can be disrupted by deviations from any of its five main underlying conditions.
What are the five evolutionary mechanisms?
There are five key mechanisms that cause a population, a group of interacting organisms of a single species, to exhibit a change in allele frequency from one generation to the next. These are evolution by: mutation, genetic drift, gene flow, non-random mating, and natural selection (previously discussed here).
What is Underdominance selection?
How does overdominance affect evolutionary process?
Is Underdominance an example of balancing selection?
Underdominance is the case where heterozygotes are less fit than homozygotes: for two alleles A and B at a given locus, both AA and BB individuals are more fit than AB heterozygotes. This is the opposite of overdominance, a form of balancing selection, where heterozygotes have a higher fitness than both homozygotes.