- General selection model
The General Selection Model (GSM) is a model of
population genetics that describes how a population's genotype will change when acted upon by natural selection.Equation
The General Selection Model is encapsulated by the equation:
Delta q=frac{pq ig [q(W_2-W_1) + p(W_1 - W_0)ig ] }{overline{W :where:::p is the frequency of the dominant gene::q is the frequency of the recessive gene::Delta q is the rate of evolutionary change of the frequency of the recessive gene::W_0,W_1, W_2 are the relative fitnesses of homozygous dominant, heterozygous, and homozygous recessive 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, ig [q(W_2-W_1) + p(W_1 - W_0)ig ] , refers to the mean effect of an allele substitution. In essence, this term quantifies what effect genetic changes will have on fitness.
ee also
*Darwinian Fitness
*Hardy-Weinberg principle
*Population genetics External links
* [http://www.mun.ca/biology/scarr/2900_GSM_derivation.htm Derivation of the General Selection Model]
* [http://bio.research.ucsc.edu/~barrylab/Shawn/Biology%20175/Homework%20Answer%20Key%202005.pdf Population Genetics Homework] (pdf)
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