Which of the following statement is incorrect?

Options

A. Viroids lack a protein coat.
B. Viruses are obligate parasites.
C. Infective constituent in viruses is the protein coat.
D. Prions consist of abnomally folded proteins.

Answer

To determine which statement is incorrect among the given options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Evaluate the first statement**: "Viroids lack a protein coat."
- Viroids are indeed infectious agents that consist solely of a short strand of RNA without a protein coat. This statement is correct.

2. **Evaluate the second statement**: "Viruses are obligate parasites."
- Viruses cannot reproduce on their own and must infect a host cell to replicate. They rely on the host's cellular machinery for their life processes. This statement is also correct.

3. **Evaluate the third statement**: "Infective constituent in viruses is the protein coat."
- This statement is misleading. While viruses do have a protein coat (capsid), the infective constituent of a virus is actually its genetic material (either DNA or RNA), which is essential for the virus to replicate within a host. Thus, this statement is incorrect.

4. **Evaluate the fourth statement**: "Prion consists of abnormally folded protein."
- Prions are indeed infectious agents composed of misfolded proteins that can cause neurodegenerative diseases. This statement is correct.

### Conclusion:
The incorrect statement is the third one: "Infective constituent in viruses is the protein coat."

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