Which of the following is correct about the genome of viroid?

Options

A. It comprises of RNA having high molecular weight.
B. It comprises of either DNA or RNA.
C. It comprises of RNA associated with proteins.
D. It comprises of RNA having low molecular weight.

Answer

To determine which statement is correct about the genome of viroids, we need to analyze the characteristics of viroids.

### Step-by-Step Solution:

1. **Understanding Viroids**: Viroids are the smallest known infectious agents. They are distinct from viruses as they do not have a protein coat.

**Hint**: Remember that viroids are simpler than viruses and lack a protein structure.

2. **Composition of Viroids**: The genome of viroids consists solely of RNA. Specifically, it is made up of single-stranded circular RNA.

**Hint**: Focus on the type of nucleic acid that viroids contain.

3. **Size of the Genome**: The length of the RNA in viroids ranges from approximately 250 to 400 nucleotides. This indicates that viroids have a small genome.

**Hint**: Consider the implications of having a small number of nucleotides on molecular weight.

4. **Molecular Weight**: Given the small size of the RNA, the molecular weight of viroid RNA is also low.

**Hint**: Recall that molecular weight is directly related to the number of nucleotides present.

5. **Evaluating Options**:
- **Option 1**: States that viroids comprise RNA having high molecular weight. This is incorrect because their RNA is low in molecular weight due to its small size.
- **Option 2**: Claims that viroids comprise either DNA or RNA. This is incorrect as viroids only contain RNA.
- **Option 3**: Suggests that viroids comprise RNA associated with protein. This is also incorrect since viroids do not have a protein coat.
- **Option 4**: States that viroids comprise RNA having low molecular weight. This is correct based on our analysis.

6. **Conclusion**: The correct statement about the genome of viroids is that it comprises RNA having low molecular weight.

### Final Answer:
**Option 4: It comprises RNA having low molecular weight.**