A system of site-specific recombination (q.v.) found in the yeast and based on the yeast two-micron plasmid. This plasmid is an autonomously replicating, circular plasmid of 6,318 base pairs, which exists in many copies in most strains of S. cerevisiae (q.v.). It encodes a site-specific recombinase (q.v.) called the FLP (pronounced ‘flip') protein. FLP acts on the FLP recombination target (FRT) located within two 599-base pair inverted repeats in the plasmid DNA and catalyzes recombination between the inverted repeats. This recombination event inverts, or ‘flips', part of the plasmid with respect to the remainder, and this is essential for plasmid amplification. FLP can also induce recombination between direct FRT repeats or between FRTs on different DNA molecules. In the former case, the recombination event results in excision of intervening DNA and an FRT. This fact has been exploited to experimentally induce site-specific recombination in Drosophila and other organisms. In Drosophila this is done by placing FLP under the control of a heat shock protein promoter, and the gene under study between two flanking FRT direct repeats. These DNAs are then integrated into the Drosophila genome by germ line transformation (q.v.). Under heat-shock conditions, FLP catalyzes recombination between the FRTs, resulting in excision of the gene of interest. The descendants of cells without such a gene show a null phenotype. This system can thus produce somatic or germ line mosaics for specific genes.
Subjects: Genetics and Genomics.