Which method f cellular defence is common in almost all eukaryotic organisms ?

Options

A. RNA interference
B. Reverse transcirption
C. VNTR
D. Phagocytosis

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which method of cellular defense is common in almost all eukaryotic organisms.

2. **Evaluating the Options**:
- **Option A: RNA interference (RNAi)** - This is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules.
- **Option B: Reverse transcriptase** - This is an enzyme used to generate complementary DNA (cDNA) from an RNA template, not primarily a defense mechanism.
- **Option C: VNTR (Variable Number Tandem Repeats)** - These are repeating sequences in DNA that are used mainly in genetic profiling, not a defense mechanism.
- **Option D: Phagocytosis** - This is a process where cells engulf and digest foreign particles, commonly seen in immune responses.

3. **Identifying the Common Method**:
- RNA interference (RNAi) is a crucial mechanism for regulating gene expression and is utilized by various eukaryotic organisms as a defense against viruses and transposons. It allows cells to silence specific genes, effectively regulating their own genetic material.

4. **Conclusion**: Based on the evaluation, the method of cellular defense that is common in almost all eukaryotic organisms is **RNA interference (RNAi)**.

5. **Final Answer**: The correct answer is **Option A: RNA interference**.