Isolation and characterization of Df(2R)BSC427 Stacey Christensen, Kim Cook and Kevin Cook Bloomington Stock Center Indiana University Df(2R)BSC427 was isolated as a FLP recombinase-induced recombination event involving PBac{RB}e04001 and P{XP}d00680. The deletion was isolated as a chromosome lacking miniwhite markers in progeny of P{hsFLP}1, y1 w1118; PBac{RB}e04001/P{XP}d00680 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.RB3}BSC427 from the segment of PBac{RB}e04001 to the left of its FRT site and the segment of P{XP}d00680 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(2R)BSC427 predicted from the Release 5 genomic coordinates of the transposable element insertions sites are 52A10;52D2. It failed to complement Df(2R)BSC308 and Df(2R)Exel6285.