Which of the following statements is incorrect ?

Options

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

Answer

To determine which statement is incorrect, we will evaluate each option one by one.

### Step-by-Step Solution:

1. **Evaluate Option 1: "Viroids lack a protein coat."**
- Viroids are indeed the smallest infectious pathogens known, consisting solely of a short strand of circular RNA without a protein coat.
- **Conclusion:** This statement is **correct**.

2. **Evaluate Option 2: "Viruses are obligate parasites."**
- Viruses can only replicate inside the living cells of a host organism, making them obligate parasites. They cannot reproduce independently outside of a host.
- **Conclusion:** This statement is **correct**.

3. **Evaluate Option 3: "Infective cause to end viruses is a protein coat."**
- The infective component of viruses is not just the protein coat (capsid) but also includes the nucleic acid (DNA or RNA) inside. The statement is somewhat misleading as it implies that the protein coat alone is responsible for infectivity.
- **Conclusion:** This statement is **incorrect**.

4. **Evaluate Option 4: "Prions consist of abnormal folded proteins."**
- Prions are indeed misfolded proteins that can induce other proteins to misfold, leading to disease. This statement is accurate.
- **Conclusion:** This statement is **correct**.

### Final Answer:
The incorrect statement is **Option 3: "Infective cause to end viruses is a protein coat."**

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