Self duplication does not occur in :-

Options

A. Mitochondria
B. Centrioles
C. Chloroplast
D. Ribosome

Answer

To determine where self-duplication does not occur, we need to analyze the options provided: mitochondria, centrioles, chloroplasts, and ribosomes.

### Step-by-Step Solution:

1. **Understanding Self-Duplication**: Self-duplication refers to the ability of an organelle or structure to replicate itself independently.

2. **Analyzing Mitochondria**:
- Mitochondria are known as semi-autonomous organelles because they possess their own DNA.
- This DNA allows them to replicate independently of the cell cycle.
- **Conclusion**: Mitochondria can self-duplicate.

3. **Analyzing Chloroplasts**:
- Similar to mitochondria, chloroplasts also have their own DNA.
- They are also considered semi-autonomous and can replicate independently.
- **Conclusion**: Chloroplasts can self-duplicate.

4. **Analyzing Centrioles**:
- Centrioles are involved in cell division and play a role in organizing the mitotic spindle.
- They duplicate during the cell cycle, specifically during the S phase.
- **Conclusion**: Centrioles can self-duplicate.

5. **Analyzing Ribosomes**:
- Ribosomes are the sites of protein synthesis in the cell.
- They do not have their own DNA and cannot replicate independently.
- Ribosomes are assembled from ribosomal RNA and proteins in the nucleolus and do not undergo self-duplication.
- **Conclusion**: Ribosomes do not self-duplicate.

6. **Final Answer**: Based on the analysis, the correct answer is **ribosomes**, as they do not have the capability for self-duplication.