Per1^tm1Ual

A cassette containing neomycin acetyl-transferase (neo) flanked by two FRT sites was inserted into a bacterial artificial chromosome encompassing the Per1 locus (clone bMQ-339m04). Two loxP sites flanking exon 4-16 of Per1 were introduced to delete exons 4-16 and the reading frame could be resumed in exon 22, thereby deleting almost the entire gene. The neo cassette for selection in ES cells was between exon 3 in the short arm of homology (1.4 kb) and the loxP site upstream of exon 4. The loxP site downstream of exon 16 was followed by the long arm of homology (4 kb) containing exons 17-22. (J:342930)