Transgenic construct used to characterize a potential insulator fragment. Encodes two divergently transcribed reporters; lacZ driven by en enhancer and promoter sequence and a mini-w gene. A 555bp fragment that extends from 543bp upstream to 12bp downstream of the gt transcription start site (PRE1.1) has been inserted in between the en enhancer and promoter sequence. This PRE1.1 fragment contains two extended pho-phol consensus-binding sites.