FLP-mediated recombination between the two progenitor insertions (P{XP}Tbhd01344 and P{XP}Tbhd10000) has deleted the genomic sequence between them, producing a 9.2kb deletion that includes the first and second exons of Tbh. The deletion affects isoforms RA, RB and RC, but not isoform RD. A residual P{XP-U} element remains at the site of the deletion.