Currently, it has believed that sheep scrapie consists of more than 20 strains with different biological phenotypes, including different incubation periods; lesion profiles; biochemical properties of the disease-associated prion protein (PrPSc), a misfolded form of the cellular prion protein (PrPC); and neuroanatomical PrPSc distribution patterns in inbred mice [7–9]. The gene discussed is PRNP; the disease is scrapie.