Separation of common environment and dominance effects with classic kinship correlation models

Abstract

Common family environmental effect (γ²) and dominance effect (d² ) are usually confounded; either or both may make the sib‐sib correlation larger than the parent‐child correlation. The classic three kinship correlations (parent‐parent, parent‐offspring, sib‐sib) can accommodate either dominance (Model D) or common family environment effects (Model C), but not both. The relationship between the various components of the three correlations of Models D and C are given. In order to include both dominance and common family environment effects, a fourth correlation, that between half‐sibs, is added to the system which enables us to separate the dominance effects from the common family environments effects. Half‐sibs may constitute a potentially new source material for study of quantitative inheritance. The principle of the constant heredity/environment ratio is discussed.