GAL4 system in drosophila: A fly geneticist's swiss army knife

The last decade has seen an enormous expansion in the genetic toolbox of model organisms. This has been particularly apparent in the fruitfly, Drosophila melanogaster, in which the development of these tools and their ongoing extension, along with the completion of the genome sequence has allowed for the analysis of most any process. One particularly elegant example of tool development was the creation of the GAL4/UAS system for targeted gene expression in Drosophila. In addition to helping make Drosophila one of the most genetically tractable metazoans, this system has also helped Drosophila attract attention from the biotechnology industry as a viable means to investigate the function of genes implicated in a wide variety of medically and economically important processes. In this article, we review the GAL4/UAS system in Drosophila and the numerous extensions that have morphed it into a veritable Swiss army knife for the analysis of gene function.