The P{CoinFLP-longGMR-FLAG::Cas9(R691A)-T2A-H2B-2xNG} construct contains "longGMR" regulatory sequences that are separated from a coding sequence by a disruptive sequence cassette. The coding sequence consists of a transcript that encodes two open reading frames separated by a T2A linker (this allows for separate translation of each protein). The first ORF encodes Cas9(R691A) tagged with Tag:FLAG. The second ORF consists of Histone2B tagged with 2xmNeonGreen. The disruptive cassette contains a transcriptional STOP sequence plus two pairs of mutually incompatible FRT sites (FRT and FRT3) which are arranged such that a single FLP-mediated recombination event, excising either the FRT-flanked sequence or the FRT3-flanked sequence can occur in a stochastic manner, with no further recombination possible. If excision of the FRT3-flanked sequence occurs, the STOP sequence is still present and the coding sequence is not expressed, while excision of the FRT-flanked sequence removes the STOP cassette, allowing expression of Tag:FLAG-tagged Cas9(R691A) and 2xmNeonGreen-tagged Histone2B under the control of the longGMR regulatory sequences.