Q. What is a prion?
The prion is an infectious (transmissible) protein able to replicate by transforming other proteins into a copy of the prion. The mechanism of the copying is not yet understood by science.
The hypothesis emerge from research about a nervous system disease known as the Creutzfeldt-Jacob disease, epidemiologically associated to a bovine disease called bovine spongiform encephalitis (the mad cow disease). The Research discovered that the infectious agent that causes those diseases, suprisingly, was a protein capable of copying itself and of being transmitted by ingestion (the reason why meat from contaminated animals cannot be consumed), inoculation and even heredity.