The PBac{WHr} transgene represents the reconstituted transgenic element generated in vivo when FLP is used to induce recombination between the FRT sites of two insertions of the PBac{WH} transgene. Like PBac{WH}, PBac{WHr} contains UAS regulatory sequences at its 5' end, oriented so that in the presence of a GAL4 driver, transcription from UAS is directed outwards from this end of the element. This can result in misexpression of neighbouring genomic loci when the element is inserted in the genome. In addition it contains a long (199bp) FRT site, a w^+mC marker and a gypsy insulator sequence (at the 3' end of the element, downstream of the marker allele). PBac{WHr} is typically generated as part of a deletion-generation strategy; when the two insertions are in trans and are in the appropriate relative orientation, FLP-mediated recombination can result in deletion of the genomic region between the two original insertions along with production of the reconstituted PBac{WHr} element at the recombination point.