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Why Does the Genotype Not Congeal?
John R. G. Turner
Vol. 21, No. 4 (Dec., 1967), pp. 645-656
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2406761
Page Count: 12
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1) When we consider two or more loci, the degree of overlap of generations affects our forecast of the way in which a population will evolve. With completely over-lapping generations there is no tendency for loci which do not interact epistatically at the phenetic level to develop gametic excess (linkage disequilibrium). With non-overlapping generations, such loci do tend to develop gametic excess, but only if they are closely linked and selection is strong. In all generation systems loci which interact epistatically at the phenetic level tend to develop gametic excess. Epistatic interaction is probably common. 2) The equation which describes changes of fitness in a population polymorphic for two loci predicts that, at stable equilibria, selection will favor closer linkage between loci which have gametic excess. 3) This raises the question why recombination still occurs, or why all organisms are not as some Oenothera species, with a condensed genotype. 4) The fitness equation for three loci shows that, in contrast to the predictions with two loci, fitness will sometimes decrease when linkage becomes tighter. As this effect grows stronger the greater the number of loci, it prevents condensation of the genotype, and keeps recombination at an optimum.
Evolution © 1967 Society for the Study of Evolution