A sequence cassette has been introduced into the attP site present in TI{TI}Tre1^attP, restoring a wild-type Tre1 transcription unit (including introns) with a Hsp70 termination sequence at the 3' end and flanked on each side by an FRT site. This results in a conditional allele in which Tre1 function can be disrupted by using FLP recombinase to excise this artificial FRT cassette. The Tre1-containing FRT cassette is followed by a splice acceptor site and GAL4. A single loxP site is present downstream of the driver sequence (markers present in the progenitor insertion and donor plasmid have been removed using P1cre).