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.
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.
Drosophila melanogaster
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.
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, linkage disequilibrium (LD) is the non-random association of alleles at different loci in a given population.

- Linkage disequilibrium

What sets population genetics apart from newer, more phenotypic approaches to modelling evolution, such as evolutionary game theory and adaptive dynamics, is its emphasis on such genetic phenomena as dominance, epistasis, the degree to which genetic recombination breaks linkage disequilibrium, and the random phenomena of mutation and genetic drift.

- 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.

2 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 worst of these mutations are selected against, leading to the loss of other alleles that are genetically linked to them, in a process of background selection.

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

A population bottleneck can result in a loss of heterozygosity. In this hypothetical population, an allele has become fixed after the population repeatedly dropped from 10 to 3.

Population structure (genetics)

Presence of a systematic difference in allele frequencies between subpopulations.

Presence of a systematic difference in allele frequencies between subpopulations.

A population bottleneck can result in a loss of heterozygosity. In this hypothetical population, an allele has become fixed after the population repeatedly dropped from 10 to 3.
A map of the locations of genetic samples of several African populations (left) and principal components 1 and 2 of the data superimposed on the map (right). The principal coordinate plane has been rotated 16.11° to align with the map. It corresponds to the east-west and north-south distributions of the populations.

Population structure is an important aspect of evolutionary and population genetics.

It is also possible to use unlinked genetic markers to estimate each individual's ancestry proportions from some K subpopulations, which are assumed to be unstructured.