Duplication of centrioles is observed during

Options

A. S - Phase
B. `G_2` - Phase
C. `G_1`- Phase
D. both (B) and ( C )

Answer

To solve the question regarding the duplication of centrioles, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Cell Cycle Phases**:
- The cell cycle consists of several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis).
- Each phase has specific functions related to cell growth, DNA replication, and preparation for division.

2. **Identifying the S Phase**:
- The S phase is specifically known as the Synthesis phase.
- During this phase, DNA replication occurs, which means that the genetic material is duplicated.

3. **Centrioles Duplication**:
- In addition to DNA replication, the S phase is also the time when centrioles, which are essential for cell division, are duplicated.
- This ensures that when the cell divides, each daughter cell receives a complete set of centrioles.

4. **Evaluating Other Phases**:
- **G1 Phase**: This phase involves cell growth and the synthesis of cellular components but does not involve the duplication of centrioles.
- **G2 Phase**: This phase is a preparation phase for mitosis where the cell checks for errors and synthesizes proteins necessary for mitosis, but centrioles are not duplicated here.
- **Both B and C**: Since neither G1 nor G2 involves centriole duplication, this option is also incorrect.

5. **Conclusion**:
- The correct answer to the question is that the duplication of centrioles is observed during the **S phase** of the cell cycle.

### Final Answer:
The duplication of centrioles is observed during the **S phase** of the cell cycle.

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