Transgenic construct used to study the role of Trl in position effect variegation. Consists of a w+* minigene, an FRT cassette containing a mutated 212bp 'd1' sequence (a sequence from downstream of the w locus) in which the Trl protein binding sequence (TC)[[8]] has been replaced with ACACAGCCGGCACACA, a 201bp spacer and then UAS sites.