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The effects of normalizing and disruptive selection on genes for recombination

Published online by Cambridge University Press:  14 April 2009

J. Maynard Smith
J. Maynard Smith
Affiliation:
School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, U.K.
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Deterministic simulations have been carried out of populations under normalizing and disruptive selection for a trait determined by genes with additive effects at six loci. In some simulations a pair of alleles at a seventh locus determined the rate of recombination between the seven loci. Normalizing selection with a single optimum, fixed or fluctuating, invariably led to genetic homozygosity. If the optimum fluctuates widely, the approach to homozygosity may be accompanied by a large decline in the mean fitness of the population. Disruptive selection was simulated by having two ‘niches’ with separate optima and separate density-dependent regulation, but with the adult population mating randomly. If the optima are widely separated, this leads to stable polymorphism. Selection produced linkage disequilibrium, normalizing selection causing repulsion and disruptive selection coupling between + and − alleles. This linkage disequilibrium accelerates the phenotypic response to selection, but delays changes in gene frequency. Selection always favoured alleles for low recombination at the expense of alleles for high recombination.

Type
Research Article
Information
Genetics Research , Volume 33 , Issue 2 , April 1979 , pp. 121 - 128
Copyright
Copyright © Cambridge University Press 1979

References

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