Genomic sequence that includes the last two exons of rhea and the last exon of CG6638 has been deleted and replaced by a cassette containing: 1. a splice acceptor site followed by stop codons and an SV40 polyA terminator and 2: a Disc\RFPDsRed.3xP3.cUa marker. The inserted DNA is flanked by inverted attP sites (thus it can subsequently be replaced using recombination-mediated cassette exchange).