Using the estimates of additive genetic variance and dominance variance as well as the regression coefficient of heterozygotes on the sums of the component homozygotes (βY-x) and the inverse of the regression coefficient of the sum of the two homozygotes on their heterozygotes (l/fβY-x} with respect to viability estimated by the Cy method, it was tested whether or not frequency-dependent selection is a general rule with respect to viability polygenes. Two types of frequency-dependent selection models were considered: (1) gene frequency-dependent model and (2) zygotic frequency-dependent model. The βy.x and 1/βx-y values predicted on the basis of the frequency-dependent selection models and the ratio of the dominance variance to the additive variance are inconsistent with the actual estimates of these parameters for the Florida, Ishigaki-jima (Japan), Raleigh (N.C.) and Aomori (Japan) populations. The same oonclusion was obtained for newly arisen polygenic viability mutations. Thus, it is speculated that frequency dependent selection is not a general rule for viability polygenes as well as polymorphic isozyme genes.
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