A αTub84B promoter is fused upstream of a "SPARC3-I-OUT-GAL80" module that contains: an attP site of 38bp, the GAL80 repressor, a second attP site (60bp, full-length site), spacer sequence and an attB site. Ribozyme sequences are also present (to prevent leaky expression in the absence of phiC31:int). phiC31:int catalyzes irreversible recombination between the attB site and one of the two attP sites; if the attP site upstream of the GAL80 repressor is utilized, GAL80 is excised (allowing GAL4-driven expression of any effectors present in the animal), while if the attP site downstream of the GAL80 repressor is utilized, GAL80 is retained (preventing GAL4-driven expression). The recombination reaction that results in loss of GAL80 is expected to occur sporadically due to the upstream attP site in the "SPARC3-I-OUT-GAL80" module being truncated.