Df(2L)BSC860 was isolated as a FLP recombinase-induced recombination event involving PBac{WH}sNPFf06876 and P{XP}d05431. The deletion was isolated as a chromosome lacking miniwhite markers in progeny of P{hsFLP}1, y1 w1118; PBac{WH}sNPFf06876/P{XP}d05431 males crossed to w1118; P{hs-hid}2, wgSp-1/SM6a 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}BSC860 from the segment of P{XP}d05431 to the left of its FRT site and the segment of PBac{WH}sNPFf06876 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}d05431 to be Release 3 genomic coordinate 20280511 on chromosome arm 2L. This corresponds to 38C5 on the Release 3 and Release 5 genome maps. The predicted position of PBac{WH}sNPFf06876 on the Release 5 map is 38B1. Consequently, the cytological breakpoints of Df(2L)BSC860 are predicted to be 38B1;38C5. Df(2L)BSC860 failed to complement barrL305.