The P{CFD4FLPOUT-fz2-fz3} construct contains two sgRNAs, with each flanked by a distinct fluorescent reporter. The transgene also contains two pairs of mutually incompatible FRT sites (FRT and FRT3) arranged such that a single FLP-mediated recombination event excises one of the two sgRNAs (plus one of the reporters) in a stochastic manner, with no further recombination possible. The construct has the following structure: FRT site - Avic\GFP3xP3.cUa marker - sgRNA1 (fz2U6.fz2+fz3.CFD4FLPOUT) - FRT3 site - FRT site - sgRNA2 (fz3U6.fz2+fz3.CFD4FLPOUT) - Disc\RFPmCh.3xP3.cUa marker - FRT3 site.
U6 promoter sequences drive expression of a fz2 sgRNA (TATGACTGGCACTCCGTAACCGG).
U6 promoter sequences drive expression of a fz3 sgRNA (CATAATGGCCCGGTGGCATCCGG).