During which phase(s) of cell cycle amount of DNA in a cell remains at 4C level if the initial amount is denoted an 2C

Options

A. `G_2 and G_1`
B. `G_1 and S`
C. only `G_2`
D. `G_2 ` and M

Answer

To determine during which phase(s) of the cell cycle the amount of DNA in a cell remains at the 4C level when the initial amount is denoted as 2C, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Cell Cycle Phases**:
- The cell cycle consists of several phases: G1, S, G2, and M (mitosis).
- In G1 phase, the cell has a DNA content of 2C.
- In S phase, DNA replication occurs, and the amount of DNA doubles from 2C to 4C.
- In G2 phase, the cell prepares for mitosis, and the DNA content remains at 4C.
- During M phase, the cell divides, and the DNA content is distributed into two daughter cells.

2. **Identify DNA Content in Each Phase**:
- **G1 Phase**: 2C (initial amount).
- **S Phase**: DNA is being replicated, so it transitions from 2C to 4C.
- **G2 Phase**: The DNA content is fully replicated and remains at 4C.
- **M Phase**: The DNA is separated into two sets, so at the beginning of mitosis, there is still a presence of 4C, but it will soon divide into 2C for each daughter cell.

3. **Determine the Phase(s) with 4C DNA Content**:
- The DNA content is at 4C during the G2 phase when the cell has completed DNA replication and is preparing for mitosis.
- During the M phase, while the DNA is technically at 4C at the start, it is in the process of dividing, so it is not stable at 4C for the entire phase.

4. **Conclusion**:
- The amount of DNA in a cell remains at 4C level primarily during the G2 phase.

### Final Answer:
The amount of DNA in a cell remains at 4C level during the **G2 phase** of the cell cycle.

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