Final answer:
Prions are proteinaceous infectious particles that do not contain any genetic material. They are smaller than viruses and consist of only proteins, without DNA or RNA.
Step-by-step explanation:
Prions are proteinaceous infectious particles that do not contain any genetic material. They are smaller than viruses and consist of only proteins, without DNA or RNA. They were initially considered impossible, but the work of Stanley Prusiner has proven their existence.