The Relative Viabilities of Alternative Human Genotypes

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Abstract
The relative viability of human heterozygotes is investigated for 2 groups of loci. Group A includes serum antigen systems and polymorphisms demonstrated after electrophoresis by general stains or histochemical methods. Group B includes dominantly inherited traits and enzyme deficiencies. The 2 types of offspring of the mating of a heterozygote and a homozygote are expected to occur in the segregation ratio of 1:1. For lico where there is complete penetrance and complete ascertainment of sibs, significant deviations from this ratio can be ascribed to selection at the locus or at a locus in linkage disequilibrium. The complication of linkage disequilibrium is eliminated by analysis of a large number of traits and there is apparently a prevalence of loci with heterozygote advantage. The estimates of viability differentials would be improved by the analysis of more pedigrees from a disparate sample of traits.