A targeting vector was designed to insert a loxP site upstream of exon 4, and a frt-flanked neomycin resistance (neo) cassette followed by a second loxP site downstream of exon 6 of the interleukin 6 receptor alpha chain (Il6ra) gene. Flp mediated recombination removed the neo cassette leaving exons 4 through 6 floxed. (J:160966)