The RNAi process, found only in in eukaryotes, is initiate by

Options

A. ds RNA fragments
B. da DNA fragments
C. ss DNA fragments
D. ss RNA fragments

Answer

To solve the question regarding the initiation of the RNA interference (RNAi) process in eukaryotes, we can break it down step by step:

### Step-by-Step Solution:

1. **Understanding RNAi**:
- RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. This process is primarily found in eukaryotic organisms.

**Hint**: Remember that RNAi is a method of gene regulation and is specific to eukaryotes.

2. **Role of Dicer Enzyme**:
- The RNAi process is initiated by the enzyme called Dicer. This enzyme is crucial for processing RNA molecules.

**Hint**: Dicer is the key enzyme that starts the RNAi process.

3. **Types of RNA Fragments**:
- The question lists several types of RNA and DNA fragments: double-stranded RNA (dsRNA), double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and single-stranded RNA (ssRNA).
- Among these, it is important to identify which type is involved in the initiation of RNAi.

**Hint**: Focus on the types of RNA that Dicer acts upon.

4. **Identifying the Correct Fragment**:
- Dicer specifically acts on double-stranded RNA (dsRNA) fragments. It cleaves these long dsRNA molecules into smaller fragments known as small interfering RNA (siRNA), which are typically about 21 nucleotides in length.

**Hint**: Dicer processes dsRNA into smaller fragments, which are essential for the RNAi mechanism.

5. **Conclusion**:
- Based on the function of Dicer and the types of fragments listed, the RNAi process in eukaryotes is initiated by double-stranded RNA fragments.

**Final Answer**: The correct option is **first: double-stranded RNA fragments**.