Isolation and characterization of Df(1)BSC275 Stacey Christensen and Kevin Cook Bloomington Stock Center Indiana University Df(1)BSC275 was isolated as a FLP recombinase-induced recombination event involving P{XP}Pfrxd04341 and PBac{RB}e01713. The deletion was isolated as a chromosome lacking miniwhite markers in progeny of P{XP}Pfrxd04341/PBac{RB}e01713; MKRS, P{hsFLP}86E/+ females crossed to Binsinscy/Y males. These females 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.RB3}BSC275 from the segment of P{XP}Pfrxd04341 to the left of its FRT site and the segment of PBac{RB}e01713 to the right of its FRT site. Its presence was verified using the PCR methods and primers described in Parks et al. with the substitution of the primer 5'-CCAATGCGTTTATTTCAGGTCACG-3' for the RB3' plus or RB3' minus primer in the Hybrid PCR protocol in the Supplementary Methods. The cytological breakpoints of Df(1)BSC275 predicted from the Release 4 genomic coordinates of the transposable element insertions sites are 18C8;18D3. It failed to complement car1.