A genetic scheme for isolating modifiers of Parkinson's disease genes in Drosophila. Deficiencies (Df) from the Bloomington deficiency kits were crossed individually into the park or Pink1 knockdown mutant background. F1 progeny were scored for potential phenotypic enhancement (i.e. an increase in the penetrance of the wing phenotype) or suppression (i.e. a decrease in the penetrance of the wing phenotype). Abbreviations: En, enhancement; Su, suppression; tub-GAL4, tubulin-GAL4.