Sequence encoding part of the Fab-7 boundary element has been inserted into the attP site present in TI{TI}Fab-7attP50, reconstituting a mutant Fab-7 element that contains only the HS1 and HS3 nuclease-hypersensitive regions (deletion coordinates are 3R:16898074..16898913 , release 6 genome). A loxP site and an FRT site are present downstream of the inserted sequence.