In a diploid cell, at which stage of cell cycle, the amount of DNA is doubled

Options

A. `G_(1) and G_(2)"phase"`
B. `G_(0)"phase"`
C. `S, G_(2)` and M-phase
D. S-phase

Answer

To determine at which stage of the cell cycle the amount of DNA is doubled in a diploid cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the 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 and activities.

2. **Identify the S Phase**: The S phase is known as the Synthesis phase. This is the critical phase where DNA replication occurs.

3. **DNA Replication**: During the S phase, each chromosome in the diploid cell is replicated. This means that each chromosome is copied, resulting in two identical sister chromatids for each chromosome.

4. **Effect on DNA Amount**: Before the S phase, a diploid cell has 2n amount of DNA (where n is the number of unique chromosomes). After the S phase, the amount of DNA effectively doubles to 4n because each chromosome now consists of two sister chromatids.

5. **Conclusion**: Therefore, the amount of DNA in a diploid cell is doubled during the S phase of the cell cycle.

### Final Answer:
The amount of DNA in a diploid cell is doubled during the **S phase** of the cell cycle.

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