Background selection

Definition

Background selection refers to the process through which deleterious mutations are removed from a population due to the effects of natural selection, impacting the genetic variation at linked neutral sites. This phenomenon can reduce the overall genetic diversity of a population by constraining the evolutionary potential of neutral alleles that are located near harmful mutations on the same chromosome. Understanding this concept is essential for grasping how both positive and negative selection shape genetic landscapes over time.

5 Must Know Facts For Your Next Test

1. Background selection can lead to reduced levels of genetic diversity in populations by filtering out deleterious alleles, which can also affect linked neutral variations.
2. This process works differently in large versus small populations, where genetic drift may play a larger role in small populations, potentially countering background selection.
3. It can influence patterns of linkage disequilibrium, where alleles at different loci are inherited together more often than expected by chance.
4. Background selection highlights the interplay between positive and negative selection, as it removes harmful mutations but can also impede the rise of beneficial ones due to linkage.
5. This concept is significant in understanding how historical selective pressures shape current genomic structures and evolutionary trajectories.

Review Questions

• How does background selection impact genetic variation within a population?
  • Background selection impacts genetic variation by removing deleterious mutations from a population, which can consequently lower the overall genetic diversity at linked neutral sites. This reduction in variation occurs because neutral alleles that are located near harmful mutations may be negatively affected by the selection against those mutations. Thus, while background selection serves to enhance population fitness by eliminating harmful genes, it can simultaneously limit the evolutionary potential by constraining beneficial neutral variations.
• Compare and contrast background selection with genetic hitchhiking and explain their implications for understanding evolution.
  • Background selection and genetic hitchhiking are both processes that involve the influence of selection on linked alleles, but they act in opposite directions. Background selection removes deleterious mutations, leading to decreased genetic diversity at linked neutral sites, while genetic hitchhiking occurs when a beneficial mutation increases the frequency of nearby neutral alleles due to positive selection. Both concepts underscore the complex dynamics of how natural selection shapes genetic variation and evolutionary outcomes, highlighting that both negative and positive selections can influence allele frequencies in populations.
• Evaluate the role of background selection in shaping genomic architectures and its importance in contemporary evolutionary studies.
  • Background selection plays a crucial role in shaping genomic architectures by influencing patterns of genetic variation across populations. Its significance lies in how it affects not only current genetic diversity but also evolutionary trajectories by removing deleterious alleles while potentially stifling beneficial ones due to linkage. In contemporary evolutionary studies, understanding background selection allows researchers to better interpret genome-wide patterns, draw connections between genetic diversity and adaptation, and develop models that reflect the true dynamics of evolution within populations under various selective pressures.

Related terms

Neutral theory: A theory in evolutionary biology that suggests most genetic variation within populations is due to random drift of neutral mutations rather than positive selection.

Genetic hitchhiking: The process whereby an allele increases in frequency because it is linked to a beneficial mutation that is undergoing positive selection.

Purifying selection: A form of natural selection that removes deleterious alleles from a population, thus preserving the fitness of the population.