Directional selection

Simply, directional selection is a pathway of natural selection in which one uncommon phenotype is selected over a more common phenotype. In population genetics, directional selection is a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction. Under directional selection, the advantageous allele increase in frequency independently of its dominance relative to other alleles; that is, even if the advantageous allele is recessive, it will eventually become fixed. Directional selection stands in contrast to balancing selection where selection may favor multiple alleles, and is the same as purifying selection which removes deleterious mutations from a population.

See also

• Balancing selection
• Disruptive selection
• Negative selection (natural selection)
• Stabilizing selection

References

• Sabeti PC, et. al. (2006). "Positive Natural Selection in the Human Lineage". Science 312.
• Pickrell JK, Coop G, Novembre J et. al. (May 2009). "Signals of recent positive selection in a worldwide sample of human populations". Genome Research.