Final answer:
A prion is a proteinaceous infectious agent associated with spongiform encephalopathies, responsible for diseases like mad cow disease or kuru. Prions are composed entirely of proteins and do not contain DNA or RNA. They bind to and convert the normal form of the protein into the infectious form, leading to brain damage and degenerative diseases.
Step-by-step explanation:
A prion is a proteinaceous infectious agent associated with spongiform encephalopathies, which are fatal neurodegenerative diseases. Prions are composed entirely of proteins and do not contain DNA or RNA. They are responsible for diseases like mad cow disease or kuru. Once introduced into the body, the infectious form of the prion protein (PrPSC) binds to the normal form (PrPC) and converts it to the infectious form, leading to the exponential increase of the PrPSC protein and the formation of lesions in the brain.