Which of the following is correct about phases of the cell cycle ?

Options

A. In `G_1` - phase , DNA content is double the amount of DNA present in the original cell.
B. DNA replication takes place in S - phase.
C. A short interphase is followed by a long mitotic phase.
D. `G_2` - phase follows mitotic phase.

Answer

To solve the question regarding the phases of the cell cycle, let's analyze the options step by step based on the information provided in the video transcript.

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**:
- The cell cycle consists of several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis).
- Interphase includes G1, S, and G2 phases, and is the longest part of the cell cycle.

2. **Analyzing Each Option**:
- **Option A**: "In G1 phase DNA content is double the amount of DNA present in the original cell."
- This statement is incorrect. In G1 phase, the DNA content is the same as the original cell (2N). DNA replication occurs in the S phase, not in G1.

- **Option B**: "DNA replication takes place in S phase."
- This statement is correct. The S phase is specifically where DNA synthesis occurs, doubling the DNA content from 2N to 4N (though the number of chromosomes remains the same).

- **Option C**: "A short interphase is followed by a long mitotic phase."
- This statement is incorrect. Interphase is actually the longest part of the cell cycle, while the M phase (mitotic phase) is relatively short.

- **Option D**: "G2 phase follows mitotic phase."
- This statement is incorrect. G2 phase occurs before the M phase, not after.

3. **Conclusion**:
- After analyzing all the options, the only correct statement is **Option B**, which states that DNA replication takes place in the S phase.

### Final Answer:
The correct statement about the phases of the cell cycle is **Option B**: "DNA replication takes place in S phase."