Fig. 1. The GheF screening method. Males of the indicated genotype were treated with the chemical mutagen EMS as described in Materials and methods. The mutagenized males were mated to the GMR-hid ey-FLP (GheF), FRT80 tester females. F1 offspring of this cross were screened for a modification, usually a suppression, of the GMR-hid eye ablation phenotype. Suppressor mutants were recovered, retested and established as balanced stocks. Only recessive suppressors were maintained; dominant suppressors were discarded.