Transgenic construct used to characterize the Fab-8 boundary element. An 8kb XhoI-SalI fragment from the regulatory region downstream of the Abd-B gene fragment has been inserted upstream of a lacZ reporter regulated by a Ubx promoter. The XhoI-SalI fragment contains Fab-8 (boundary) and iab-8PRE (silencer) sequences and iab-7 and iab-8 initiator elements. It is inserted so that the proximal iab-8 sequences are located close to the promoter.