RNA like particles that cause disease are

Options

A. Virus
B. Viroid
C. Prion
D. Mycoplasma.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks for RNA-like particles that cause disease. We need to identify which of the provided options fits this description.

2. **Analyzing the Options:**
The options given are:
- Virus
- Viroid
- Prion
- Mycoplasma

3. **Evaluating Each Option:**
- **Virus:**
- Viruses are infectious agents that consist of nucleic acid (either DNA or RNA) surrounded by a protein coat. While some viruses contain RNA, they are not classified as "RNA-like particles" since they have a more complex structure.
- **Viroid:**
- Viroids are indeed RNA particles. They are small, circular, single-stranded RNA molecules that lack a protein coat (capsid) and are known to cause diseases in plants. This makes viroids a strong candidate for the answer.
- **Prion:**
- Prions are misfolded proteins that cause neurodegenerative diseases. They do not contain RNA, so they do not fit the description of RNA-like particles.
- **Mycoplasma:**
- Mycoplasma are the smallest self-replicating bacteria and do not resemble RNA particles. They are prokaryotic organisms and thus do not fit the criteria.

4. **Conclusion:**
After evaluating all the options, the only correct answer that fits the description of RNA-like particles that cause disease is **Viroid**.

**Final Answer: Viroid**

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