title: Heritability of heterozygosity offers a new way of understanding why dominant gene action contributes to additive genetic variance.
abstract: Whenever allele frequencies are unequal, nonadditive gene action contributes to additive genetic variance and therefore the resemblance between parents and offspring. The reason for this has not been easy to understand. Here, we present a new single-locus decomposition of additive genetic variance that may give greater intuition about this important result. We show that the contribution of dominant gene action to parent-offspring resemblance only depends on the degree to which the heterozygosity of parents and offspring covary. Thus, dominant gene action only contributes to additive genetic variance when heterozygosity is heritable. Under most circumstances this is the case because individuals with rare alleles are more likely to be heterozygous, and because they pass rare alleles to their offspring they also tend to have heterozygous offspring. When segregating alleles are at equal frequency there are no rare alleles, the heterozygosities of parents and offspring are uncorrelated and dominant gene action does not contribute to additive genetic variance.
authors.affiliation: Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. pirmin.nietlisbach@ieu.uzh.ch.
authors.forename: Pirmin
authors.initials: P
authors.lastname: Nietlisbach
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JT, United Kingdom.
authors.forename: Jarrod D
authors.initials: JD
authors.lastname: Hadfield
mesh_terms: D005787:Gene Frequency; D005799:Genes, Dominant; D014644:Genetic Variation; D040941:Heredity; D006579:Heterozygote; D008957:Models, Genetic
keywords: Nonadditive gene action; parent-offspring covariance; quantitative genetics