The pM37_p2 plasmid consists of a recombination-mediated cassette exchange (RMCE) cassette flanked by a pair of inverted attP sites. Inside the attP sites is a cassette flanked by a pair of direct FRT sites. This in turn contains an intron phase 2 'Trojan GAL4' gene trap element (composed of a splice acceptor site followed by the T2A peptide, the GAL4 coding sequence and an SV40 polyadenylation signal), followed by the Avic\GFP^3xP3.cLa marker allele. pM37_p2 is used to generate donor plasmids that can be used in combination with CRISPR/Cas9 to insert the attP-flanked RMCE cassette into a defined location in the genome by homology directed repair; the donor plasmid is generated by adding homology arms to each side of the pM37_p2 RMCE cassette using the Type IIS restriction sites in plasmid.