Answer: Abnormally folded infectious protein particles with no nucleic acid.
- A Composed entirely of double-stranded DNA packaged within a protective capsid
- B Abnormally folded infectious protein particles with no nucleic acid
- C Small RNA molecules enclosed within a protective protein coat
- D Fragments of peptidoglycan derived from the bacterial cell wall
Correct answer: B. Abnormally folded infectious protein particles with no nucleic acid
Explanation: Prions are unusual infectious agents composed only of abnormally folded proteins, with no nucleic acid component, unlike viruses (nucleic acid plus protein coat) and viroids (free RNA only).
Whittaker's five-kingdom system (1969) groups all cellular life by cell structure and nutrition; viruses, viroids, and lichens fall outside this system entirely since they aren't independently classifiable as one of the five.
Concept context
Whittaker's five kingdom system covering Monera, Protista, Fungi, plus viruses, viroids, and lichens. A foundational NEET chapter on how living organisms are grouped.