general selection model

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

: $\backslash Delta\; q=\backslash frac\{pq\; \backslash big[q(W\_2-W\_1)\; +\; p(W\_1\; -\; W\_0)\backslash big\; ]\}\{\backslash overline\{W\}\}$

:where:

::$p$ is the frequency of allele A1

::$q$ is the frequency of allele A2

::$\backslash Delta\; q$ 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.

::$\backslash overline\{W\}$ 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 $\backslash Delta\; Q$ is proportional to the genetic variation.

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

The remainder of the equation, $\backslash big[q(W\_2-W\_1)\; +\; p(W\_1\; -\; W\_0)\backslash big\; ]$, refers to the mean effect of an allele substitution. In essence, this term quantifies what effect genetic changes will have on fitness.

• Darwinian fitness
• Hardy–Weinberg principle
• Population genetics

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Category:Population genetics