Define prions.

Explanation

Prions were discovered by Stanley B. Prusiner in the year 1982 and are proteinaceous infectious particles. They are the causative agents for about a dozen fatal degenerative disorders of the central nervous system of humans and other animals. For example Creutzfeldt - Jakob Disease (CJD), Bovine Spongiform Encephalopathy (BSE) - commonly known as mad cow disease and scrapie disease of sheep.