The logarithm of fitness as a function of the number of deleterious mutations. Synergistic epistasis is represented by the red line - each subsequent deleterious mutation has a larger proportionate effect on the organism's fitness. Antagonistic epistasis is in blue. The black line shows the non-epistatic case, where fitness is the product of the contributions from each of its loci.
Gene flow is the transfer of alleles from one population to another population through immigration of individuals.
Drosophila melanogaster
Examples of speciation affecting gene flow.
Gene flow is the transfer of alleles from one population to another population through immigration of individuals. In this example, one of the birds from population A immigrates to population B, which has fewer of the dominant alleles, and through mating incorporates its alleles into the other population.
Marine iguana of the Galapagos Islands evolved via allopatric speciation, through limited gene flow and geographic isolation.
The Great Wall of China is an obstacle to gene flow of some terrestrial species.
Current tree of life showing vertical and horizontal gene transfers.

In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another.

- Gene flow

The main processes influencing allele frequencies are natural selection, genetic drift, gene flow and recurrent mutation.

- Population genetics
The logarithm of fitness as a function of the number of deleterious mutations. Synergistic epistasis is represented by the red line - each subsequent deleterious mutation has a larger proportionate effect on the organism's fitness. Antagonistic epistasis is in blue. The black line shows the non-epistatic case, where fitness is the product of the contributions from each of its loci.

3 related topics

Alpha

In this simulation, each black dot on a marble signifies that it has been chosen for copying (reproduction) one time. fixation in the blue "allele" occurs within five generations.

Genetic drift

Change in the frequency of an existing gene variant (allele) in a population due to random chance.

Change in the frequency of an existing gene variant (allele) in a population due to random chance.

In this simulation, each black dot on a marble signifies that it has been chosen for copying (reproduction) one time. fixation in the blue "allele" occurs within five generations.
Ten simulations of random genetic drift of a single given allele with an initial frequency distribution 0.5 measured over the course of 50 generations, repeated in three reproductively synchronous populations of different sizes. In these simulations, alleles drift to loss or fixation (frequency of 0.0 or 1.0) only in the smallest population.
Changes in a population's allele frequency following a population bottleneck: the rapid and radical decline in population size has reduced the population's genetic variation.
When very few members of a population migrate to form a separate new population, the founder effect occurs. For a period after the foundation, the small population experiences intensive drift. In the figure this results in fixation of the red allele.

The Hardy–Weinberg principle states that within sufficiently large populations, the allele frequencies remain constant from one generation to the next unless the equilibrium is disturbed by migration, genetic mutations, or selection.

The corrected mathematical treatment and term "genetic drift" was later coined by a founder of population genetics, Sewall Wright.

In the ABO blood group system, a person with Type A blood displays A-antigens and may have a genotype IAIA or IAi. A person with Type B blood displays B-antigens and may have the genotype IBIB or IBi. A person with Type AB blood displays both A- and B-antigens and has the genotype IAIB and a person with Type O blood, displaying neither antigen, has the genotype ii.

Allele frequency

Relative frequency of an allele at a particular locus in a population, expressed as a fraction or percentage.

Relative frequency of an allele at a particular locus in a population, expressed as a fraction or percentage.

In the ABO blood group system, a person with Type A blood displays A-antigens and may have a genotype IAIA or IAi. A person with Type B blood displays B-antigens and may have the genotype IBIB or IBi. A person with Type AB blood displays both A- and B-antigens and has the genotype IAIB and a person with Type O blood, displaying neither antigen, has the genotype ii.

In population genetics, allele frequencies are used to describe the amount of variation at a particular locus or across multiple loci.

In natural populations natural selection (adaptation mechanism), gene flow, and mutation combine to change allele frequencies across generations.

Example scientific modelling. A schematic of chemical and transport processes related to atmospheric composition.

Coalescent theory

Model of how alleles sampled from a population may have originated from a common ancestor.

Model of how alleles sampled from a population may have originated from a common ancestor.

Example scientific modelling. A schematic of chemical and transport processes related to atmospheric composition.

In the simplest case, coalescent theory assumes no recombination, no natural selection, and no gene flow or population structure, meaning that each variant is equally likely to have been passed from one generation to the next.

The mathematical theory of the coalescent was developed independently by several groups in the early 1980s as a natural extension of classical population genetics theory and models, but can be primarily attributed to John Kingman.