Explanation

Prions have a distinct extracellular form made up of protein. The prion particle does not contain any nucleic acid. However, it is infectious and known to cause a variety of diseases in animals such as scrapie in sheep, bovine spongiform encephalopathy in cattle (BSE or mad cow disease), chronic wasting disease in deer, elk and kuru and a form of Creutzfeldt-Jakob Disease (CJD) in humans.