Recombination replaced the neomycin resistance cassette in Etn2tm1Kymm with a loxKR3, a 287 bp genomic fragment containing murine early transposon (ETn) from cosmid clone C3, FRT site, puromycin (puro) resistance cassette and lox2272 site. Flp-mediated recombination removed the puro cassette. (J:195133)