Stabilizing selection
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Overview
Stabilizing selection, also referred to as purifying selection, is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. Put another way, extreme values of the character are selected against. This is probably the most common mechanism of action for natural selection.
A classic example of this is human birth weight. Babies of low weight lose heat more quickly and get ill from infectious disease more easily, whereas babies of large body weight are more difficult to deliver through the pelvis. However, the recent improvements in human nutrition in developed countries has led to rising rates of caesarean sections, since babies are routinely out-growing the female reproductive tract.[1]
Stabilizing selection operates most of the time in most populations. This type of selection acts to prevent divergence of form and function. In this way, the anatomy of some organisms, such as sharks and ferns, has remained largely unchanged for millions of years.
Stabilizing selection can sometimes be detected by measuring the fitness of the range of different phenotypes by various direct measures, but it can also be detected by a variety of tests of molecular sequence data, such as Ka/Ks ratios, changes in allele frequency distributions, and the McDonald Kreitman test.[2][3]
See also
References
- ↑ Liston WA (2003). "Rising caesarean section rates: can evolution and ecology explain some of the difficulties of modern childbirth?". Journal of the Royal Society of Medicine 96 (11): 559–61. PMID 14594971.
- ↑ Sheets HD, Mitchell CE (2001). "Why the null matters: statistical tests, random walks and evolution". Genetica 112-113: 105–25. PMID 11838761.
- ↑ McDonald JH, Kreitman M (1991). "Adaptive protein evolution at the Adh locus in Drosophila". Nature 351 (6328): 652–4. PMID 1904993.
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 |
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Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
