The cell cycle is regulated by checkpoints during the ___ phases.

Options

A. `G_(1),S` and `G_(2)`
B. `G_(1),S` and C
C. `G_(1),G_(2)`, and M
D. None of these

Answer

To answer the question, "The cell cycle is regulated by checkpoints during the ___ phases," we can follow these steps:

### Step-by-Step Solution:

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

2. **Identify the Checkpoints**: There are three main checkpoints in the cell cycle:
- **G1 Checkpoint**: This checkpoint occurs at the end of the G1 phase. It assesses whether the cell is ready to enter the S phase and begin DNA replication.
- **G2 Checkpoint**: This checkpoint occurs at the end of the G2 phase, before the cell enters mitosis (M phase). It checks for DNA damage and ensures that all DNA has been replicated correctly.
- **M Checkpoint**: This checkpoint occurs during the M phase (mitosis). It ensures that all chromosomes are properly attached to the spindle apparatus before the cell proceeds with division.

3. **Determine the Phases with Checkpoints**: From the above information, we can conclude that the checkpoints are present during the G1, G2, and M phases of the cell cycle.

4. **Formulate the Answer**: Therefore, the cell cycle is regulated by checkpoints during the G1, G2, and M phases.

### Final Answer:
The cell cycle is regulated by checkpoints during the G1, G2, and M phases.

---