FLP::GS encodes a ligand-inducible recombinase that is composed of the FLP recombinase encoded by the Saccharomyces cerevisiae 2μ plasmid fused to a truncated ligand-binding domain from the Homo sapiens progesterone receptor (PGR, HGNC:8910). The presence of the ligand-binding domain results in recombinase activity being dependent on the presence of the progesterone mimic mifepristone (RU486) (FBrf0229249).