Question

RNA without protein capsid -

• A. Viroid
• B. Lichen
• C. Prion
• D. Virus

Hint:

Viroid = RNA only. Prion = Protein only. Virus = Nucleic acid + Protein coat.

Answer 1

The Correct Option is A

Concept: Various infectious agents differ in their structural organization. Some contain nucleic acids and proteins, while others may contain only nucleic acid or only protein. Viroids are the smallest known infectious agents and are composed solely of RNA molecules.

Step 1: Understand what a viroid is. Viroids were discovered by T.O. Diener. A viroid consists of: \[ \text{Only circular single-stranded RNA} \] and lacks any protective protein coat.

Step 2: Compare with other options. Viruses possess both nucleic acid and a protein coat called a capsid. Prions are infectious protein particles and do not contain nucleic acids. Lichens are symbiotic associations between algae and fungi.

Step 3: Identify the correct answer. The infectious agent containing RNA but lacking a protein capsid is the viroid. \[ \boxed{\text{Viroid}} \] Hence, the correct answer is \[ \boxed{(A)\ \text{Viroid}} \]