The single coding exon was flanked by loxP sites. An EGFP reporter cassette, was inserted downstream of the floxed coding exon. Cre-mediated recombination resulted in the deletion of the coding exon in the germline, and the expression of the EGFP minigene under the control of the endogenoous promoter. A, frt-flanked neomycin resistance cassette was eliminated in vivo by crossing to a FLPe deleter strain. (J:251437)