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:
In words:
The product of the relative frequencies, formula_7, is a measure of the genetic variance. The quantity pq is maximized when there is an equal frequency of each gene, when formula_8. In the GSM, the rate of change formula_9 is proportional to the genetic variation.
The mean population fitness formula_6 is a measure of the overall fitness of the population. In the GSM, the rate of change formula_9 is inversely proportional to the mean fitness formula_6—i.e. when the population is maximally fit, no further change can occur.
The remainder of the equation, formula_13, refers to the mean effect of an allele substitution. In essence, this term quantifies what effect genetic changes will have on fitness.