20XUAS regulatory sequences are separated from sequence encoding Tag:M(mCd8a)-tagged GFP by a "SPARC2-D" module that comprises: a full-length attP site of 60bp, a STOP cassette, a second attP site (60bp, full-length site), ribozyme sequence (to prevent leaky expression in the absence of phiC31:int) and an attB site. phiC31:int catalyzes irreversible recombination between the attB site and one of the two attP sites; if the attP site upstream of the STOP cassette is utilized, the STOP cassette is excised, permitting expression of Tag:M(mCd8a)-tagged GFP, while if the attP site downstream of the STOP cassette is utilized, the STOP cassette is preserved. The "SPARC2-D" module typically results in expression of the effector (in this case Tag:M(mCd8a)-tagged GFP) in approximately 45% of cells.