Estimation of changes in genetic parameters in selected lines of mice using REML with an animal model. 1. Lean mass.

Analysis was undertaken using Restricted Maximum Likelihood (REML) with an animal model of the results of selection for 20 generations for predicted lean mass in 10-week-old male mice. There were three replicates, each comprising high, low and unselected control lines. The overall estimates of heritability (h2) and common environmental correlations (c2) from results of the first seven generations were 0.51 +/- 0.03 and 0.21 +/- 0.01, respectively. Analyses of data from different lines and different numbers of generations were undertaken but with all pedigrees and data included, which enabled inferences to be drawn on changes in variance that were not due simply to inbreeding or short-term effects of selection. Estimates of h2 were lower in selected lines than the control, increasingly so in later generations, indicating departure from the infinitesimal model assumption of unlinked additive genes each of very small effect. In addition, values of c2 became higher in high than in control or low selected lines.