In disorders such as Creutzfeldt-Jakob disease (CJD), Kuru, Gerstmann-Sträussler-Scheinker disease and familial fatal insomnia, also classified as transmissible spongiform encephalopathies (TSEs), the soluble prion protein (PrPC) acquires an abnormal conformation, known as PrPSc, which is protease resistant and acts as a seed for the misfolding of physiological PrPC (Beck et al., 1969; Gibbs and Gajdusek, 1969; Prusiner, 1982). The gene discussed is PRNP; the disease is Creutzfeldt Jacob disease.