The P{XP}, PBac{WH} and PBac{RB} insertions isolated at Exelixis, Inc. may be used to generate chromosomal deletions in an isogenic background. The method is described in Parks et al., 2004. Most of the Exel deletions in the Bloomington collection retain this isogenic background. The following stocks may be used in screens to preserve the isogenic background in new deletion stocks (see Parks et al., 2004, for details).