Which of the following best describes a prion?

• A. A bacterium that infects animal cells
• B. An infectious protein that lacks nucleic acids
• C. A small circular RNA molecule without a protein coat
• D. A virus composed of RNA and a protein coat

Answer: (B)

Verified step by step guidance

1. Understand that prions are unique infectious agents distinct from bacteria, viruses, and RNA molecules.
2. Recall that bacteria are living cells with nucleic acids and cellular structures, so prions cannot be bacteria.
3. Recognize that viruses consist of nucleic acids (DNA or RNA) enclosed in a protein coat, which prions lack.
4. Know that some infectious agents are RNA molecules without protein coats, called viroids, which are different from prions.
5. Conclude that prions are infectious proteins that lack nucleic acids, making the correct description: 'An infectious protein that lacks nucleic acids.'