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Related Concept Videos

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...
Mutation, Gene Flow, and Genetic Drift01:09

Mutation, Gene Flow, and Genetic Drift

In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).Mechanisms of Genetic VariationThe original sources of genetic variation are mutations,...
Evolution of New Traits in Microbes01:24

Evolution of New Traits in Microbes

Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under laboratory conditions. Natural selection acts on standing genetic variation, enabling the retention and amplification of beneficial traits that confer fitness advantages in changing environments.Adaptive Pigment Regulation in RhodobacterIn Rhodobacter, a genus of purple non-sulfur bacteria, light-harvesting pigments such as bacteriochlorophyll and...
Limits to Natural Selection01:38

Limits to Natural Selection

Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.For one, natural selection can only act upon existing genetic variation. Hypothetically, redtusks may enhance elephant survival by deterring ivory-seeking poachers. However, if there are no gene variants—or alleles—for redtusks, natural selection cannot increase the prevalence of...
Frequency-dependent Selection01:21

Frequency-dependent Selection

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.Positive Frequency-Dependent SelectionIn positive...
Genetic Drift03:33

Genetic Drift

Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.Life is not fair. A deer grazing contentedly in a field can have her meal cut tragically short by a bolt of lightning. If the doomed doe is one of only three in the population, 1/3 of the population’s gene pool is lost. Random events like this can...

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Related Experiment Video

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Following the Dynamics of Structural Variants in Experimentally Evolved Populations
04:52

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Published on: February 3, 2023

Mutation accumulation, soft selection and the middle-class neighborhood.

Jacob A Moorad1, David W Hall

  • 1Department of Genetics, University of Georgia, Athens, Georgia 30602-7223, USA. jmoorad@uga.edu

Genetics
|May 19, 2009
PubMed
Summary

The "middle-class neighborhood" breeding design reduces purifying selection to accumulate mutations. This method applies soft selection, potentially biasing estimates of mutation effects when social factors influence fitness.

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Area of Science:

  • Evolutionary biology
  • Population genetics

Background:

  • Purifying selection typically removes deleterious mutations.
  • Among-line fitness variation can obscure the accumulation of new mutations.

Purpose of the Study:

  • To evaluate the "middle-class neighborhood" breeding design's effectiveness in accumulating mutations.
  • To determine if this design introduces biases in estimating mutational effects.

Main Methods:

  • Utilizing a "middle-class neighborhood" breeding design.
  • Analyzing the effects of soft selection on experimental populations.
  • Investigating the role of social effects on fitness.

Main Results:

  • The breeding design effectively lessens purifying selection.
  • The design applies soft selection to the population.
  • Biased estimates of mutational effects may occur if social effects are present.

Conclusions:

  • The "middle-class neighborhood" design facilitates mutation accumulation.
  • Researchers must consider potential biases due to soft selection and social effects when interpreting results.