Prions are glycoproteins which codes for a membrane protein. Prion proteins are usually resistant to protease digestion and are not broken down by heat. Prions do not contain genetic material. CJD, Kuru and scrapie are prion diseases. Prions are thought to have a role in cell signalling rather than DNA replication. Normal prion proteins

are encoded by chromosome 20. PrPsc is characterised by increased β pleated sheets. PrPsc proteins are anchored by glycoproteins (GPI).