Directional selection

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In population genetics, directional selection occurs when natural selection favors a single phenotype and therefore allele frequency continuously shifts in one direction. Under directional selection, the advantageous allele will increase in frequency independently of its dominance relative to other alleles (i.e. 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, in other words it is directional selection in favor of the advantageous heterozygote. Directional selection is a particular mode or mechanism of natural selection.

[edit] See also

• Balancing selection
• Disruptive selection
• Stabilizing selection

[edit] References

• P. C. Sabeti, et al. Science 312, 1614 (2006) Positive Natural Selection in the Human Lineage (Review)

v • d • e Topics in molecular evolution Natural selection Background selection • Balancing selection • Directional selection • Disruptive selection • Negative selection • Stabilizing selection • Selective sweep Models Models of DNA evolution • Models of nucleotide substitution • Allele frequency • Ka/Ks ratio • Tajima's D Molecular processes Gene conversion • Gene duplication • Silent mutation • Synonymous substitution