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Related Concept Videos

Speciation Rates01:07

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Overview
Types of Selection01:46

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...
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When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.
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Detection of Rare Genomic Variants from Pooled Sequencing Using SPLINTER
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Detecting individual sites subject to episodic diversifying selection.

Ben Murrell1, Joel O Wertheim, Sasha Moola

  • 1Biomedical Informatics Research Division, eHealth Research and Innovation Platform, Medical Research Council, Tygerberg, South Africa.

Plos Genetics
|July 19, 2012
PubMed
Summary

Identifying episodic natural selection in protein-coding genes is challenging. A new method, MEME, effectively detects both episodic and pervasive positive selection, revealing widespread episodic selection previously underestimated.

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Area of Science:

  • Evolutionary biology
  • Genomics
  • Bioinformatics

Background:

  • Natural selection's impact on protein-coding genes is often transient or episodic, affecting only some lineages.
  • Current computational methods struggle to detect episodic selection, potentially underestimating positively selected sites.

Purpose of the Study:

  • To develop a novel computational method for identifying both episodic and pervasive positive selection at the site level.
  • To improve the detection of natural selection's imprint on protein-coding genes.

Main Methods:

  • Introduction of the Mixed Effects Model of Evolution (MEME).
  • Utilizing empirical and simulated data for model evaluation.
  • Comparison of MEME's performance against existing evolutionary models.

Main Results:

  • MEME accurately identifies both episodic and pervasive positive selection at individual sites.
  • The model demonstrates superior performance across diverse scenarios compared to older methods.
  • Episodic selection is found to be widespread across the analyzed data.

Conclusions:

  • Episodic selection is a common evolutionary force in protein-coding genes.
  • Previous estimates of positively selected sites likely underestimated their true prevalence.
  • MEME offers a powerful tool for uncovering the dynamics of natural selection in molecular evolution.