These sequence variants were first identified by their ability to confer resistance to scrapie in sheep (Q171R or R154H in the mammalian prion protein PrP), sporadic Creutzfeldt-Jakob disease (sCJD) in humans (E219K in PrP), and translation termination infidelity in yeast (G58D in Sup35) [6–19]. The gene discussed is PRNP; the disease is sporadic Creutzfeldt-Jakob disease.