Part of the wg first exon (including the ATG site and all the coding sequence of this exon) has been deleted by gene targeting. The deleted sequence has been replaced with the following sequence: 1. a attP site, 2: a loxP cassette which itself contains an mFRT71 cassette followed by the Scer\GAL4 coding sequence. The mFRT71 cassette contains 1: the mCherry coding region tagged with (a membrane-targeting signal (Tag:Myr(Unk)), 2: a w+* marker. The mCherry coding region is expressed under the control of the endogenous wg regulatory sequences.