Transgenic construct designed for use as a control in a chromosome-puffing assay, which can be used to define and characterize chromatin domain boundary elements. Contains a w+* minigene, a 5.2kb intronless y+t* minigene that includes the upstream wing and body enhancers, and an hsp70-lacZ fusion gene (Ecol\lacZHsp70Bb.70ZT) that includes heat shock elements in the Hsp70 upstream regulatory sequence. A pair of 36bp loxP sites have been inserted at position -893 relative to the y transcription start site (in between the y enhancers and the y coding region). Two 114bp FRT sites with a NotI site engineered between them have been inserted at position +86 within the Hsp70 5' UTR sequences.