Transgenic construct used to study sequence predicted to be a candidate Polycomb/Trithorax response element (PRE/TRE). Derived from P{UAS-lacZ.U/l5}, which contains the Ecol\lacZC4.UAS reporter and a w+mC marker; the candidate sequence, a 3kb fragment from an intron of cad (genomic coordinates 20,745,045-20,748,082), has been inserted upstream of the w+mC marker and its effects on w expression have been analyzed.