THE NONLINEARITY OF OFFSPRING-PARENT REGRESSION FOR TOTAL STERNOPLEURAL BRISTLE NUMBER OF DROSOPHILA-MELANOGASTER

A test of the linearity of the offspring-midparent regression for total sternopleural bristle number showed significant departure from linearity, with a tendency for higher heritability at higher values of the character. Offspring-midparent regression coefficients for each of four subdivisions of the total range of bristle number were not significantly different. The nonlinearity of offspring-midparent regression detected in this study may be due to either chance effects, genotypic asymmetry of genes with large effect, distribution asymmetry, or a combination of these factors. Further work is required to determine the extent and causes of nonlinearity of offspring-parent regression.