Transgenic construct used to study a Polycomb response element (PRE). It consists of 1. an FRT cassette that contains both a Rnor\Cd2αTub84B.PC marker and the the Ubx early enhancer (EE), 2. the 1.6kb bxd PRE, 3. the Ubx imaginal disc (DE) enhancer and promoter fused upstream of lacZ, and 4. a y+t* marker.