Polygenic analysis of larval locomotor activity inDrosophila melanogaster

The genetic basis of larval locomotor activity inDrosophila melanogaster was studied by comparing four strains that differ significantly in activity levels. The inbred wild-type strain Canton-S had the lowest activity level, while the relatively heterogeneous wild-type OK1 genotype had the highest. Activities could not be explained simply in terms of a difference in catecholamine levels. The analysis of heterozygous whole-chromosome effects suggested that chromosome 2 carried modifiers that increased activity, but an interchromosomal interaction balanced its effect in OK1. A sex-limited interaction countering an X-chromosome effect in Canton-S was also consistent with the conclusion that stabilizing interactions are an important part of the genetic control of this behavioral phenotype.