Sequence has been inserted into the attP site present in TI{mCherry}traKO.Cherry, resulting in a tra locus in which the tra promoter is followed by 1. an FRT cassette that contains a truncated tra cDNA and 2. the coding sequence of the female-specific tra protein (tra-F). This allows conditional production of the tra-F protein; functional tra-F protein is only produced if the FRT cassette containing the truncated cDNA is excised using FLP recombinase.