Transgenic construct used to study the Polycomb response element (PRE) from the Ubx upstream control region. Consists of an FRT cassette containing a 1.6kb fragment that encompasses the Ubx PRE, upstream of a reporter gene composed of the 806bp vg 'quadrant enhancer' from Ecol\lacZvg.806 in its endogenous orientation, a 4.1kb Ubx proximal promoter element and lacZ.