The photomicrographs show cells in various stages of the cell cycle. Identify the stage where semi - conservative replication of DNA take place.

Options

A.
B.
C.
D.

Answer

To identify the stage of the cell cycle where semi-conservative replication of DNA occurs, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Cell Cycle**: The cell cycle consists of several stages: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis).

2. **Identify the Stages of Mitosis**: The stages of mitosis include prophase, metaphase, anaphase, and telophase. These stages are involved in the division of the cell's nucleus.

3. **Focus on the S Phase**: The semi-conservative replication of DNA occurs specifically during the S phase of interphase. This is when the DNA is duplicated, ensuring that each daughter cell will receive an identical set of chromosomes.

4. **Analyze the Options**:
- **Metaphase**: Chromosomes align in the center of the cell but no DNA replication occurs.
- **Anaphase**: Chromatids are pulled apart to opposite poles but again, no DNA replication occurs.
- **Interphase**: This includes the S phase where DNA replication occurs.
- **Prophase**: Chromosomes condense and the mitotic spindle begins to form, but no DNA replication occurs.

5. **Conclusion**: The correct answer is **Interphase**, specifically during the **S phase**, where semi-conservative replication of DNA takes place.

### Final Answer:
**The stage where semi-conservative replication of DNA takes place is Interphase (S phase).**

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