The source of complementary RNA required for RNA silencing is

Options

A. infection by a virus having DNA genome
B. infection by a viroid having RNA genome
C. transposons which have copy and paste mechanism of transfer
D. transposons which have cut and paste mechanism of transfer

Answer

To solve the question regarding the source of complementary RNA required for RNA silencing, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding RNA Silencing**:
- RNA silencing, also known as RNA interference (RNAi), is a biological process in which RNA molecules inhibit gene expression or translation. This process is crucial for regulating gene expression and defending against viral infections.

2. **Identifying the Source of Complementary RNA**:
- The question asks for the source of complementary RNA that is necessary for RNA silencing. Complementary RNA is crucial as it binds to specific mRNA molecules, preventing their translation.

3. **Evaluating the Options**:
- **Option A**: Infection by a virus having an RNA genome.
- This option is plausible because viruses with RNA genomes can introduce RNA into the host cell, which may serve as a template for complementary RNA.
- **Option B**: Infection by a viroid having an RNA genome.
- Viroids are small, circular RNA molecules that can cause disease in plants but do not produce proteins. They do not serve as a source of complementary RNA for silencing.
- **Option C**: Transposons which have a copy and paste mechanism of transfer.
- Transposons, or "jumping genes," can replicate and insert themselves into different locations in the genome. They can produce RNA intermediates that may serve as complementary RNA.
- **Option D**: Transposons which have a cut and paste mechanism of transfer.
- While transposons can also use a cut and paste mechanism, the question specifies the copy and paste mechanism, which is more relevant for generating complementary RNA.

4. **Conclusion**:
- After evaluating all the options, the correct answer is **Option C**: Transposons which have a copy and paste mechanism of transfer. These transposons can generate RNA that is complementary to specific mRNA, facilitating RNA silencing.

### Final Answer:
The source of complementary RNA required for RNA silencing is **transposons which have a copy and paste mechanism of transfer**.