Isolation and characterization of Df(2L)BSC243 Stacey Christensen and Kevin Cook Bloomington Stock Center Indiana University Df(2L)BSC243 was isolated as a FLP recombinase-induced recombination event involving PBac{WH}f05591 and P{XP}d10374. The deletion was isolated as a chromosome lacking miniwhite markers in progeny of P{hsFLP}1, y1 w1118; PBac{WH}f05591/ P{XP}d10374 males crossed to w1118; P{hs-hid}2, wgSp-1/CyO females. These males were heat shocked as larvae as described in Parks et al., Nature Genetics 36: 288-292, 2004 (FBrf0175003). This cross and crosses in preceding and succeeding generations maintained the original genetic background of the Exelixis insertion stocks (Thibault et al., Nature Genetics 36: 283-287, 2004; FBrf0175002). The recombination event generated the genetic element P+PBac{XP5.WH5}BSC243 from the segment of PBac{WH}f05591 to the left of its FRT site and the segment of P{XP}d10374 to the right of its FRT site. Its presence was verified using the PCR methods and primers described in Parks et al. Exelixis, Inc. determined the insertion site of P{XP}d10374 to be at Release 3 genomic coordinate 12044040 on chromosome arm 2L. The Gene Disruption project determined the insertion site of P{XP}d10374 to be at Release 3 genomic coordinate 12044441 on arm 2L. This corresponds to 33C1 on both the Release 3 and Release 4 genome maps. The predicted position of PBac{WH}f05591 on the Release 4 map is 32F3. Consequently, the cytological breakpoints of Df(3R)BSC243 are predicted to be 32F3;33C1. It failed to complement esc5.