Possible influence of major gene heterozygosity on variation of quantitative traits.

The possible explanations for heterosis and heterozygous advantage have included the hypothesis that the metabolic versatility of heterozygotes for functional alleles of structural genes would enhance resistance to environmental insult, i.e. would result in enhanced developmental homeostasis. Evidence on this hypothesis is conflicting. The paper presents additional evidence, based on four human polymorphisms and 9 quantitative traits in a sample of mother-offspring data from Sweden. These data do not support the hypothesis of interest. Reasons for the conflicting results are discussed.