Cre-mediated reversion of inverted chromosomes. (A) Schematic view of the Cre-mediated reversion joining the 3xP3 promoter to the EGFP coding sequence resulting in EGFP expression. Note the inverted orientation of the two loxP sites in the two P-elements. w+ y– EGFP–, and w+ y– EGFP+ indicates the phenotype of the flies carrying the respective chromosomes. (B) Larvae with the genotype In (3R) 16c-83C; 20y-86E (top) and In(3R) 16c-83C;20y-86E/hsCre (the two larvae below) under UV light. Note the clonal nature of the inversion visualized by EGFP fluorescence, which can be particularly well observed at the anal plates (arrow). The expression pattern of 3xP3 in the anal plates, the gut, and the brain is as reported by Horn et al. (2000).
