Transgenic construct used to study how position effects influence transvection. Consists of: 3' P end, a loxP site, GMR regulatory sequences, the GFP coding sequence (lacking a promoter), an FRT site, a w^+mC marker, GMR regulatory sequences, a loxP site, an Hsp70 core promoter, the GFP coding sequence, an FRT site, 5' P end. In the absence of modification, GMR activity in cis can be assessed. Exposure to FLP creates a derivative (P{TV2-GMR.-FRT}) that contains a "promoterless" GFP, while exposure to P1cre creates a derivative P{TV2-GMR.-loxP} that contains an "enhancerless" GFP. These two derivatives can be combined to assess GMR activity in trans.