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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 Population Genetics?

What is Population Genetics?

A population is composed of members of the same species that simultaneously live and interact in the same area. When individuals in a population breed, they pass down their genes to their offspring. Many of these genes are polymorphic, meaning that they occur in multiple variants. Such variations of a gene are referred to as alleles. The collective set of all the alleles within a population is known as the gene pool.

Types of Selection

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...

Limits to Natural Selection

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.

Principles of Pharmacogenetics: Types of Genetic Variants

Principles of Pharmacogenetics: Types of Genetic Variants

The human genome is over 99.9% identical between individuals, yet genetic differences exist at millions of bases. The human genome contains approximately 3 million variant positions per individual, many of which are heterozygous, contributing to genetic diversity and individual traits. Genetic variations include single-nucleotide polymorphisms (SNPs), insertions, deletions, and copy number variations (CNVs).SNPs, the most common variation, involve single-base changes in DNA. These can be...

Hardy-Weinberg Principle

Hardy-Weinberg Principle

Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.

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Related Experiment Video

Updated: May 9, 2026

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Published on: February 3, 2023

Selective constraint, background selection, and mutation accumulation variability within and between human

Alan Hodgkinson¹, Ferran Casals, Youssef Idaghdour

¹Sainte Justine Research Centre, Department of Pediatrics, University of Montreal, Montreal, Canada.

|July 24, 2013

Summary

This summary is machine-generated.

Evolutionary constraint helps identify functional genome regions. This study shows populations with smaller effective sizes carry more deleterious mutations, impacting genetic load and individual health.

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Published on: July 11, 2019

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Last Updated: May 9, 2026

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

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Published on: February 3, 2023

Detection of Rare Genomic Variants from Pooled Sequencing Using SPLINTER

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Published on: June 23, 2012

Characterizing Mutational Load and Clonal Composition of Human Blood

Characterizing Mutational Load and Clonal Composition of Human Blood

Published on: July 11, 2019

Area of Science:

Genomics
Population Genetics
Evolutionary Biology

Background:

Evolutionary constraint identifies functional genomic sequences.
Interspecies divergence correlates with human fitness.
Deleterious mutation accumulation varies across populations and individuals.

Purpose of the Study:

To test differences in deleterious mutation accumulation across human populations and individuals.
To investigate the relationship between evolutionary constraint and allele frequency.
To understand the role of background selection in shaping human genetic diversity.

Main Methods:

Utilized whole genome and exome sequencing data from the 1000 Genomes Project (Phase 1).
Analyzed data from 1,092 individuals across 14 worldwide populations.
Applied high-coverage sequencing data to classify individual genomes based on mutation accumulation.

Main Results:

Minor allele frequency (MAF) varies with constraint around coding and non-coding sites, indicating background selection.
Smaller effective population sizes correlate with increased deleterious mutations and higher genetic load.
Detected variations in putatively deleterious rare alleles among 'healthy' individuals within populations.

Conclusions:

Background selection significantly shapes the human genome.
Population history influences human genetic diversity.
Personal genomic data can be used to study genetic fitness and diseases.