The Effect of Heterozygosity on Variability and Vigour

OKKING with progressive mutants in agricultural plants, the present writer wished to examine the effect of mutations, not only in the homozygous but also in the heterozygous condition.In most evolutionary discussions on mutations, their selective value has been judged from the homozygous appearance.It is generally conceived that a recessive mutation either shows no effect on viability in the single dose, or, if there is an effect, that the heterozygote directly reflects the properties of the recessive mutant.Already here it must be emphasized that this idea seems to be entirely false.Certainly some reports on ))monohybrid heterosisa have been published, with the heterozygote surpassing both homozygotes, one of which may be sublethal or lethal, but they have been ignored, or, if discussed, they are regarded as untenable.To take just two examples.