Lewontin and Hubby's paper also discussed the possible explanation of the high levels of variability by either balancing selection or neutral mutation.
12.
There are several mechanisms ( which are not exclusive within any given population ) by which balancing selection works to maintain polymorphism.
13.
Finally, balancing selection can occur through frequency-dependent selection, where the fitness of one particular phenotype depends on the distribution of other phenotypes in the population.
14.
This is an example of balancing selection between the fierce selection against homozygous sickle-cell sufferers, and the selection against the standard HgbA homozygotes by malaria.
15.
In contrast, balancing selection acts to maintain genetic variation in a population, even in the absence of " de novo " mutation, by negative frequency-dependent selection.
16.
Positive selection can, in turn, be further subdivided into directional selection, which tends toward fixation of an advantageous allele, and balancing selection, which maintains a Nei.
17.
The scientific problem has been to explain the natural function of a molecule, such as a self semidominant, or recessive; purifying selection or balancing selection ).
18.
Clarke later argued that frequency-dependent balancing selection could explain molecular polymorphisms ( often in the absence of heterosis ) in opposition to the neutral theory of molecular evolution.
19.
Mutation selection balance was originally proposed to explain how genetic variation is maintained in populations, although several other ways for deleterious mutations to persist are now recognized, notably balancing selection.
20.
Most posit balancing selection ( see polymorphism ( biology ) ), which is any natural selection process whereby no single allele is absolutely most fit, such as frequency-dependent selection and heterozygote advantage.
