THE GENETIC-BASIS OF QUANTITATIVE VARIATION - NUMBERS OF SENSORY BRISTLES OF DROSOPHILA-MELANOGASTER AS A MODEL SYSTEM

The numbers of sensory hairs of Drosophila melanogaster present an ide al model system to elucidate the genetic basis of morphological quanti tative variation. Loci affecting bristle number can be identified and their properties studied by accumulating spontaneous mutations, by P e lement mutagenesis, by mapping factors causing divergence between sele ction lines and by the association of phenotypic variation with molecu lar variation at candidate neurogenic loci. The consensus emerging fro m the application of all approaches is that much of the mutational and segregating variation affecting bristle number is attributable to all eles with large phenotypic effects at a small number of candidate loci .