General selection model explained

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.^[1]

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 = (pq [ q(W _{2-W} _{1)} + p(W _{1} - W _{0) ]})/(\overline{W) }

where:

p is the frequency of allele A1q is the frequency of allele A2\Delta q is the rate of evolutionary change of the frequency of allele A2W _{0,W} _{1,} W _{2} are the relative fitnesses of homozygous A1, heterozygous (A1A2), and homozygous A2 genotypes respectively.\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 \Delta Q is proportional to the genetic variation.

The mean population fitness

\overline{W} 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{W} —i.e. when the population is maximally fit, no further change can occur.

The remainder of the equation,

[ q(W _{2-W} _{1)} + p(W _{1} - W _{0) ]} , 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

Notes and References

1. Book: Benjamin A. Pierce. Transmission and Population Genetics. 9 January 2006. W. H. Freeman. 978-0-7167-8387-9.