General Selection Model

The general selection model (GSM) is a model of population genetics that describes how a population's allele frequencies will change when acted upon by natural selection.

Equation

The General Selection Model applied to a single gene with two alleles (let's call them A1 and A2) is encapsulated by the equation:

: $\Delta q=\frac$
:where:

::$p$ is the frequency of allele A1
::$q$ is the frequency of allele A2
::$\Delta q$ is the rate of evolutionary change of the frequency of allele A2
::$W_0,W_1, W_2$ are the relative fitnesses of homozygous A1, heterozygous (A1A2), and homozygous A2 genotypes respectively.
::$\overline$ is the mean population relative fitness.

In words:

The product of the relative frequencies, $pq$, is a measure of the genetic variance. The quantity pq is maximized when there is an equal frequency of each gene, when $p=q$. In the GSM, the rate of change $\Delta Q$ is proportional to the genetic variation.

The mean population fitness $\overline$ is a measure of the overall fitness of the population. In the GSM, the rate of change $\Delta Q$ is inversely proportional to the mean fitness $\overline$—i.e. when the population is maximally fit, no further change can occur.

The remainder of the equation, \big (W_2-W_1) + p(W_1 - W_0)\big /math>, refers to the mean effect of an allele substitution. In essence, this term quantifies what effect genetic changes will have on fitness.

See also

*Darwinian fitness
*Hardy–Weinberg principle
*Population genetics

References

{{Reflist

Population genetics