ZrchI Prnp- Prnp<-> Prnp<0> Prnp trn<1Zrch> Prnp<tm1Zrch> PrnpZH1 MGI:1888773 Prnp<0> Zurich I PrP<C> Zrch-1 Prnp<tm1Cwe> targeted mutation 1, Charles Weissmann http://identifiers.org/mgd/MGI:1888773 Null/knockout Zrch Prnp<0> PrP<0> Zurich line Prn-p<0> PrP<C>-KO Zrch 1 Prnp<0>