Transgenic construct used to study the mechanism of chromosomal boundary action. Contains two divergently transcribed reporters: a mini-w marker plus a lacZ reporter in which two ftz enhancers (UPS, upstream and NE, neurogenic) are fused upstream of Hsp70-lacZ. A scs' fragment that is flanked on both sides by an RS(I-SceI) site is present downstream of the lacZ reporter.