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Mutations

Mutations

Mutations

Mutations

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...

Mutation, Gene Flow, and Genetic Drift

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).

What is Natural Selection?

What is Natural Selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become more common within a population or species. Naturally selected traits initially arise via random genetic mutations. In order for selection to occur, there must be variation within a population, the trait controlling the variation must be heritable, and there must be an evolutionary advantage for variation in the trait.

Viral Mutations

Viral Mutations

A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material...

Conservation of Small Populations

Conservation of Small Populations

Small population sizes put a species at extreme risk of extinction due to a lack of variation, and a consequent decrease in adaptability. This weakens the chances of survival under pressures such as climate change, competition from other species, or new diseases. Large populations are more likely to survive pressures such as these, as such populations are more likely to harbor individuals that have genetic variants that are adaptive under new stresses. Small populations are much less...

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Related Experiment Video

Updated: Feb 7, 2026

Measuring Microbial Mutation Rates with the Fluctuation Assay

Measuring Microbial Mutation Rates with the Fluctuation Assay

Published on: November 28, 2019

Mutation accumulation in selfing populations under fluctuating selection.

Eddie K H Ho¹, Aneil F Agrawal¹

¹Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON M5S 3B2, Canada.

Evolution; International Journal of Organic Evolution

|July 14, 2018

Summary

This summary is machine-generated.

Selfing species face extinction due to accumulating harmful mutations. Fluctuating selection, especially when strong and autocorrelated, accelerates this genomic degradation, driving species toward extinction.

Keywords:

Fluctuating selection mutation accumulation selfing stochastic simulation

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Last Updated: Feb 7, 2026

Measuring Microbial Mutation Rates with the Fluctuation Assay

Measuring Microbial Mutation Rates with the Fluctuation Assay

Published on: November 28, 2019

The Lambda Select cII Mutation Detection System

The Lambda Select cII Mutation Detection System

Published on: April 26, 2018

Identifying Mutations by High Resolution Melting in a TILLING Population of Rice

Identifying Mutations by High Resolution Melting in a TILLING Population of Rice

Published on: September 2, 2019

Area of Science:

Evolutionary Biology
Population Genetics

Background:

Selfing species are vulnerable to extinction, potentially due to accumulating deleterious mutations, similar to Muller's ratchet.
Existing theories lack detail on gene types accumulating mutations and environmental factors accelerating genomic degradation.

Purpose of the Study:

Investigate how temporal environmental changes, causing fluctuating purifying selection, impact deleterious mutation accumulation in selfing populations.
Identify specific genomic loci and environmental conditions that exacerbate extinction risk.

Main Methods:

Simulated selfing populations with genomes containing both constant and fluctuating selection loci.
Analyzed the effects of fluctuating selection strength on deleterious mutation accumulation and fixation rates.
Assessed the role of linked selection and effective population size (N_e).

Main Results:

Loci under fluctuating selection contributed disproportionately more to deleterious mutation accumulation than those under constant selection.
Fluctuating selection increased deleterious fixation rates at constant selection loci, primarily via reduced effective population size (N_e).
Strongly autocorrelated and rare, strong bouts of fluctuating selection were particularly detrimental.

Conclusions:

Loci experiencing fluctuating selection are key drivers of genomic degradation and extinction risk in selfing species.
Environmental fluctuations, especially those with strong autocorrelation, pose a significant threat to the long-term survival of selfing populations.