Home > Allele frequency

Given a) a particular chromosome locus, b) a gene occupying that locus, c) a population of individuals carrying n loci in each of their somatic cells (e.g. two loci in the cells of diploid species, which contain two sets of chromosomes) and finally d) a variant or allele of the gene, then the allele frequency of that allele is the fraction or percentage of loci that the allele occupies within the population.

To take an example, if the frequency of an allele is 20% in a given population, then among population members, one in five chromosomes will carry that allele. Four out of five will be occupied by other variants the gene, of which there may be one or many.

Note that for diploid genes, however, the proportion of individuals that carry this allele may be up to two in five. If the allele distributes randomly, then the binomial theorem will apply: 32% of the population will be heterozygous for the allele (i.e. carry one copy of that allele and one copy of another in each somatic cell) and 4% will be homozygous (carrying two copies of the allele). So all together 36% of diploid individuals would be expected to carry an allele that has a frequency of 20%. However, alleles distribute randomly only in the absence of selectionIn the context of evolution, certain traits or alleles of a species may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively--meaning they contribute more o and under other assumptions. When these conditions apply, a population is said to be in Hardy-Weinberg equilibriumalleles: the horizontal axis shows the two allele frequencies p and q , the vertical axis shows the genotype frequencies and the three possible genotypes are represented by the different glyphs The Hardy-Weinberg principle HWP (also Hardy-Weinberg equilib.

The frequencies of all the alleles of a given gene often are graphed together as an allele frequency distributionFunctional analysis This page deals with mathematical distributions. For other meanings of distribution, see distribution (disambiguation). This article is not about probability distributions. In mathematical analysis, distributions (also known as general histogramIn statistics, a histogram is a graphical display of tabulated frequencies. That is, a histogram is the graphical version of a table which shows what proportion of cases fall into each of several or many specified categories. The categories are usually sp. Population genetics studies the different "forces" that might lead to changes in the distribution and frequencies of alleles -- in other words, to evolutionThis article is about biological evolution. For other possible meanings, see Evolution (disambiguation). Evolution generally refers to any process of change over time. However, in the context of the life sciences, evolution is a change in the genetic make. Besides selection, these forces include genetic driftGenetic drift is a mechanism of evolution that acts in concert with natural selection to change the characteristics of species over time. It is a statistical effect that arises from the role of chance in the production of offspring. Like selection, it act, mutationThis article is about mutation in biology, for other meanings see: mutation (disambiguation). Mutations are permanent, transmissible changes to the genetic material (usually DNA or RNA) of a cell. Mutations can be caused by copying errors in the genetic m and migrationMigration occurs when living things move from one biome to another. In most cases organisms migrate to avoid local shortages of food, usually caused by winter. Animals may also migrate to a certain location to breed. Bird migration is common. The longest.