In the above experiments, and in all experiments described in the remainder of this study, all PrP-expressing (tga20 and WT) mice diagnosed as terminally scrapie-sick were tested by Western blot analysis and by histology: all were invariably found to contain PrPSc in their brains (Fig. 2) and to display all typical histopathological features of scrapie including spongiosis, PrP deposition and astrogliosis (Fig. 1H). This evidence concerns the gene PRNP and scrapie.