UASt regulatory sequences drive expression of HcRed1. Marker allele that forms part of the disruptive FRT cassette located between the UASt regulatory sequences and multiple cloning site (MCS) of the pUHR cloning vector, and transgenic constructs derived from this vector. The HcRed1 coding sequence in the disruptive cassette is flanked by FRT sites and when the cassette is present, HcRed1 is expressed under the control of UASt and prevents expression of any coding sequence of interest that has been inserted into the downstream MCS. FLP-mediated recombination can be used to excise the cassette, removing the HcRed1 coding sequence and allowing expression of the downstream coding sequence of interest. Clones in which the FRT cassette has been excised can be identified by lack of HcRed1 expression.