The P{w+(-FRT)(loxP.y+)} element contains (5' to 3') a w+mW.hs marker, a single FRT site, a loxP cassette containing a y+t* marker. It can be generated in vivo by excision of the FRT cassette from a series of recombinant constructs which have themselves been generated by inserting sequence into the P{w+(FRT.attP.1360)} docking site by phiC31:int-mediated recombination.