Partitioning of variance and estimation of genetic parameters for various bristle number characters of Drosophila melanogaster

Phenotypic variance for each of several bristle number characters (abdominal, sternopleural, second and third coxal) was partitioned using both hierarchal and dialled designs. Heritabilities and genetic correlations were estimated from parent-offspring regressions and correlations and half-sib correlations. A high proportion of the genetic variance for abdominal bristle number was due to epistatic and sex-linked gene action, but most of the genetic variance for the other characters was additive autosomal. The genetic correlations among sternopleural, and second and third coxal bristle numbers were all high, but that between abdominals and sternopleurals was low, while those between abdominals and either second or third coxals were virtually zero. An appreciable proportion of the covariance between abdominal and sternopleural bristle numbers was non-additive genetic. The diallel method gave more reliable estimates of genetic parameters when non-additive or sex-linked genetic variation was present.