A 264bp portion of scro exon 2 has been deleted (the deletion is just downstream of the start codon in this exon), and replaced with a sequence cassette that contains the GAL4::p65 coding sequence and a Equa\eqFP578TagRFP.3xP3 marker. This results in GAL4::p65 being expressed under the control of the regulatory sequences of the scro RA, RB and RC transcript isoforms, while expression of the native scro RA, RB and RC transcripts is disrupted due to the presence of an SV40 transcription termination signal downstream of the GAL4::p65 coding sequence. (Expression of the scro RF isoform is not affected by the insertion).