The relative viabilities of alternative human genotypes.
The relative viability of heterozygotes is investigated for two 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 two types of offspring of the mating of a heterozygote and a homozygote are expected to occur in the segregation ratio of 1:1. For loci 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 the tentative conclusion is reached that there is 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.
D006579:Heterozygote; D006801:Humans; D008433:Mathematics; D008957:Models, Genetic; D010375:Pedigree; D012641:Selection, Genetic