In RNAi, genes are silenced using

Options

A. ssDNA
B. dsDNA
C. dsRNA
D. ssRNA

Explanation

**Step-by-Step Solution:**

1. **Understanding RNA Interference (RNAi):** RNA interference is a biological process that occurs in eukaryotic organisms. It serves as a method of cellular defense against foreign genetic elements such as viruses.

2. **Mechanism of RNAi:** In RNAi, specific messenger RNA (mRNA) molecules are silenced. This silencing occurs through the action of complementary RNA molecules that bind to the target mRNA.

3. **Role of Double-Stranded RNA (dsRNA):** The complementary RNA that is involved in the silencing process is typically double-stranded RNA (dsRNA). This dsRNA binds to the target mRNA and prevents its translation into protein, effectively silencing the gene.

4. **Sources of dsRNA:** The dsRNA can originate from various sources, including viral infections (where the virus has an RNA genome) or from mobile genetic elements like transposons that replicate through RNA intermediates.

5. **Identifying the Correct Answer:** Given the options provided:
- Single-stranded DNA
- Double-stranded DNA
- Double-stranded RNA
- Single-stranded RNA

The correct answer is **double-stranded RNA (dsRNA)**, as it is the molecule that mediates the silencing of genes in RNA interference.

**Final Answer:** In RNAi, genes are silenced using **double-stranded RNA (dsRNA)**.

---