Nxf3tm1.1Jw/Y ES cells were electroporated with the pUP108 vector used to generate the Igs8tm1Jw allele which replaces a 5.6 kb intergenic region between Tmsb15a and Armcx5 with a floxed PGK-neo selection cassette, producing a targeted conditional allele with four loxP sites. Mice carrying this floxed allele were crossed with Actb-Cre mice to delete a 350 kb region on mouse chromosome X between Armcx5 and Nxf3. (J:210663)