A sequence cassette encoding 1. the GAL4 coding sequence followed by an Hsp70 terminator sequence and 2. a Disc\RFPDsRed.3xP3.cUa marker has been inserted into the dsf start codon in exon 1. This removes all dsf coding sequences within the first exon and the first exon's 5' splice site, and allows expression of GAL4 under the control of endogenous dsf regulatory sequences.