This transgene consists of the murine Prnp with a proline to leucine substitution at codon 101 (equivalent to codon 102 in human PRNP). This construct was generated using a chimeric murine cosmid constructed by exchanging the BamHI-SalI fragment containing the open reading frame from a recombinant NZW genomic clone for the corresponding fragment in an ILn/J mouse cosmid. An approximate 100-nucleotide region flanking codon 101 leucine was modified to yield DNA sequence homology to hamster Prnp while retaining amino acid homology to mouse Prnp. Analysis indicated that this line carries approximately 64 haploid transgene copies inserted into a single autosomal site. Three lines were created: 174, 180, and 196.