A plasmid (pBT340, with the sequence pattB-pCA-GFP-pA-FRT5-pPGK-Flpo-pA) was injected into mouse embryos homozygous for a targeted mutation that had an Frt-flanked sequence. Several random insertions were obtained and analyzed for Flpo activity and ubiquitous GFP expression. When crossed to wild-type mice, all F1 progeny from one founder showed Flp-mediated excision. (J:171979)