ABSTRACT
This chapter reviews the quantitative genetic principles of three topics which are critical to the application of selection indices and which are also central to the overall topic of artificial selection. These topics include methods used for estimating unobservable genotypic values, the general principles of heritability, coheritability, and response to selection, and methods used for estimating genotypic covariances and correlations. Genotypic value is the average phenotypic performance of a particular genotype when it can be evaluated in a complete reference set of environments. Thus, for a particular genotype, its genotypic value might be considered as the hypothetical average performance over several years within a particular geographic region. Genotypic values for different traits may be correlated because they are influenced in part by genes which affect both traits or because they are influenced by different genes which are linked on the same chromosome.
