ratio heritability Philippe Rocca-Serra In a planned experiment where to covariance (genotype x environment) can be controlled and held at 0, the heritability is defined as the ratio of the variance of the genotypic variables to the variance of the phenotypic variables. H2 = Var(G)/Var(P) H2 is the broad-sense heritability. This reflects all the genetic contributions to a population's phenotypic variance including additive, dominant, and epistatic (multi-genic interactions), as well as maternal and paternal effects, where individuals are directly affected by their parents' phenotype, for example, milk production in mammals. https://en.wikipedia.org/wiki/Heritability ready for release