An FRT cassette that contains a f+t13 marker separates the Ubx promoter from a coding cassette composed of GAL4 and lacZ (the two coding regions are separated by an internal ribosome entry site).
Used as marker for clonal analysis in wing; FRT-containing variant blocks EcollacZ expression; see expression data for P{GAL4-lacZ-Ubx(-FRT).dC} at EcollacZUbx.PdCRA.