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Related Concept Videos

Types of Selection01:46

Types of Selection

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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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A complementation test is a simple cross to identify whether the two mutations are located on the same gene or different genes. It was first performed by Edward Lewis in the 1940s while working on fruit flies. He developed the test to identify the location and arrangement of different mutations on chromosomes.
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The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a...
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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.
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Balancing selection on the complement system of a wild rodent.

Mridula Nandakumar1, Max Lundberg2, Fredric Carlsson2

  • 1Department of Biology, Lund University, Lund, Sweden. mridula.nandakumar@biol.lu.se.

BMC Ecology and Evolution
|May 25, 2023
PubMed
Summary

Pathogen pressure drives genetic diversity in host immune systems. Complement genes, particularly FCNA, show balancing selection, indicating coevolutionary adaptation in pathogen interactions.

Keywords:
Balancing selectionBank volesComplement systemMyodes glareolusPathogen-mediated selection

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Area of Science:

  • Evolutionary biology
  • Immunology
  • Genetics

Background:

  • Pathogen-driven selection shapes host genetic diversity, especially in the immune system.
  • The complement system, crucial for innate immunity, interacts directly with pathogens.
  • Previous analyses of pathogen-mediated balancing selection on complement genes were limited.

Purpose of the Study:

  • To investigate genetic diversity and balancing selection signatures in complement genes within a wild bank vole population.
  • To determine if complement genes are targets of pathogen-mediated balancing selection.

Main Methods:

  • Whole-genome resequencing data from 31 wild bank voles were analyzed.
  • Genetic diversity and balancing selection were assessed in 44 complement genes.
  • The Hudson-Kreitman-Aguadé (HKA) test and localized scans were used to identify selection signatures.

Main Results:

  • Complement genes exhibited higher standardized beta values, indicative of balancing selection, compared to the genome-wide average.
  • The complement gene FCNA (a pattern recognition molecule) showed a significant signature of balancing selection.
  • Balancing selection in FCNA was localized to exonic regions involved in ligand binding.

Conclusions:

  • Balancing selection is a significant evolutionary force acting on innate immune system components.
  • The complement system, specifically genes like FCNA involved in direct pathogen interaction, is a key target of this selection.
  • These findings support the coevolutionary arms race between hosts and pathogens impacting immune gene diversity.