Maintenance of genetic variability under strong stabilizing selection: a two-locus model

Article Abstract:

The relationship between stabilizing selection and recombination was examined through a study on a two locus model which has additive contributions to the phenotype. Results revealed that for a double heterozygote with the optimum phenotype and having different contributions to the loci, any form of symmetric stabilizing selection can preserve genetic variability for as long as selection is sufficiently stronger than linkage. An analysis of the quadratic fitness function yielded results demonstrating that polymorphic equilibria can remain stabile even if selection strength is not much greater than recombination. Genetic variability is not necessarily eliminated by stabilizing selection.

Genetic aspects

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Mutation models and quantitative genetic variation

Article Abstract:

A regression mutation model was used to analyze genetic variances within and between populations. The model, which bridges the gap between the random walk and the house-of-cards mutation models, defines the regression coefficient, gamma, wherein when gamma=1, the model becomes the random walk mutation model and when gamma=0, the model becomes the house-of-cards mutation model. Results showed that the random walk mutation model may allocate too much variation for the change of populations means under neutrality and thus, should not be interpreted as a null hypothesis of neutrality.

Genetics

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Pleiotropic models of polygenic variation, stabilizing selection, and epistasis

Article Abstract:

An analysis of pleiotropic models is done based on the premise that stabilizing selection on an additive polygenic trait is observable for any dependence of fitness on genotype. Data on fitness functions are applied to a general mutation-selection balance model and to three specific variability models including the overdominant, symmetric and an additive epistatic model. Populations with low levels of variability had apparent stabilizing strengths of the order Vm/Vg. The epistasis model was suggested for use in analysis of data with a large number of loci.

Research, Heredity

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