Bosch JA, Tran NH, Hariharan IK. CoinFLP: a system for efficient mosaic screening and for visualizing clonal boundaries in Drosophila. Development. 2015 Feb 1;142(3):597-606. PMID: 25605786; PMCID: PMC4302991.
From the abstract: "... The CoinFLP system described here enables mosaic screens in the context of gene knockdown or overexpression by automatically generating a reliable ratio of mutant to wild-type tissue in a developmentally controlled manner. CoinFLP-Gal4 generates mosaic tissues composed of clones of which only a subset expresses Gal4. ..."