Cell theory is not applicable to

Options

A. Viruses
B. Viroids
C. Prions
D. All the above

Answer

**Step-by-Step Solution:**

1. **Understanding Cell Theory**:
- The cell theory states that all living organisms are composed of cells, and cells are the basic unit of life. It also states that all cells arise from pre-existing cells.

2. **Analyzing the Options**:
- **Viruses**:
- Viruses consist of genetic material (either DNA or RNA) surrounded by a protein coat (capsid). They lack cellular structures and cannot reproduce independently; they require a host cell to replicate. Therefore, viruses do not fit the criteria of the cell theory.

- **Viroids**:
- Viroids are small infectious agents that consist solely of a short strand of RNA without a protein coat. They do not have cellular structures and can only replicate within a host cell. Thus, they also do not conform to the cell theory.

- **Prions**:
- Prions are misfolded proteins that can induce other proteins to misfold, leading to disease. They do not have any genetic material and do not exhibit cellular characteristics. Hence, prions also do not adhere to the cell theory.

3. **Conclusion**:
- Since all three options (viruses, viroids, and prions) do not fit within the framework of the cell theory, the correct answer is **"all the above."**

**Final Answer**: Cell theory is not applicable to **all the above** (viruses, viroids, prions).

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