In animal cell DNA replication begins during the

Options

A. S-phase
B. `G_(1)`-phase
C. `G_(2)`- phase
D. M-phase

Answer

To answer the question "In animal cell DNA replication begins during the," we will analyze the different phases of the cell cycle and identify where DNA replication occurs.

### Step-by-Step Solution:

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

2. **Identifying the M Phase**:
- The M phase is where mitosis occurs, which is the process of cell division. During this phase, the cell divides into two daughter cells. Importantly, there is no DNA replication occurring during this phase. Therefore, M phase is **not** the correct answer.

3. **Examining the G1 Phase**:
- The G1 phase is the first gap phase where the cell grows and prepares for DNA replication. However, DNA replication does not occur during this phase; it is primarily focused on cell growth and preparation for the next phase. Thus, G1 phase is also **not** the correct answer.

4. **Looking at the G2 Phase**:
- The G2 phase is the second gap phase that occurs after DNA has been replicated. During this phase, the cell continues to grow and prepares for mitosis, including synthesizing proteins necessary for cell division. However, DNA replication has already occurred by this point, so G2 phase is **not** the correct answer.

5. **Identifying the S Phase**:
- The S phase, or Synthesis phase, is where DNA replication takes place. During this phase, the DNA is duplicated, resulting in two identical sets of chromosomes. This is essential for ensuring that each daughter cell receives the same genetic material during cell division. Therefore, the S phase is the correct answer.

### Conclusion:
In animal cells, DNA replication begins during the **S phase** of the cell cycle.

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