Direct repeats of loxP sites flank the wing and body enhancers of the y gene (-2880bp and -900bp relative to the y transcriptional start), and direct repeats of FRT sites flank the y promoter (-900bp and +1625bp relative to the y transcriptional start), in a 15.6kb genomic fragment containing the y gene, including 7.5 kb of 5' and 2.1 kb of 3' flanking DNA. The FRT site at -900bp is 5' to the loxP site at -900bp.