Which of the following statements 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 abnormally folded proteins

Answer

To determine which statement is incorrect, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Option A: Viroids lack a protein coat.**
- Viroids are known to be the smallest infectious agents and consist solely of a short strand of circular RNA. They do not have a protein coat.
- **Conclusion:** This statement is **correct**.

2. **Option B: Viruses are obligate parasites.**
- Viruses can only replicate inside a host cell, which makes them obligate parasites. They rely on the host's cellular machinery for reproduction.
- **Conclusion:** This statement is **correct**.

3. **Option C: Infective constituent in viruses is the protein coat.**
- In viruses, the infective constituent is not the protein coat; rather, it is the nucleic acid (either DNA or RNA) that is housed within the protein coat. The protein coat serves as protection for the nucleic acid but does not carry the infective properties.
- **Conclusion:** This statement is **incorrect**.

4. **Option D: Prions consist of abnormally folded proteins.**
- Prions are indeed infectious agents composed solely of protein, and they are characterized by their abnormal folding. This abnormal structure is responsible for their ability to induce misfolding in normal proteins.
- **Conclusion:** This statement is **correct**.

### Final Answer:
The incorrect statement among the options provided is **Option C: Infective constituent in viruses is the protein coat.**

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