Which of the following best describes a prion?

• A. An infectious protein that lacks nucleic acids
• B. A complete virus particle composed of nucleic acid and protein coat
• C. A small, circular RNA molecule that infects plants
• D. A virus that infects bacteria

Answer: (A)

Verified step by step guidance

1. Understand the definition of a prion: Prions are infectious agents composed solely of protein, without any nucleic acids (DNA or RNA).
2. Recall that viruses consist of nucleic acids (either DNA or RNA) enclosed in a protein coat, so they are not prions.
3. Recognize that small, circular RNA molecules that infect plants are called viroids, not prions.
4. Identify that viruses infecting bacteria are called bacteriophages, which are distinct from prions.
5. Conclude that the best description of a prion is 'an infectious protein that lacks nucleic acids' because it matches the unique characteristic of prions.