During cell cycle, two molecules of DNA are present in chromosome during

Options

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

Answer

To determine during which phase of the cell cycle two molecules of DNA are present in a chromosome, we can analyze the different phases of the cell cycle step by step.

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**: The cell cycle is divided into two main phases: the M phase (mitotic phase) and interphase. Interphase is further divided into three phases: G1, S, and G2.

2. **G1 Phase**: In the G1 phase, the cell is metabolically active and prepares for DNA replication. However, DNA replication has not yet occurred, so there is only one molecule of DNA per chromosome.

3. **S Phase**: The S phase is where DNA replication occurs. During this phase, each chromosome is duplicated, resulting in two identical sister chromatids. However, at the end of the S phase, the chromosomes are still not separated, so they are still considered as one chromosome with two sister chromatids.

4. **G2 Phase**: After the S phase, the cell enters the G2 phase. In this phase, the cell continues to grow and prepares for mitosis. At this point, the chromosomes consist of two identical sister chromatids, meaning there are two molecules of DNA present in each chromosome.

5. **M Phase**: During the M phase, the cell undergoes mitosis, where the sister chromatids are separated into two daughter cells. At this point, the two molecules of DNA are separated, and each daughter cell will receive one molecule of DNA.

6. **Conclusion**: Therefore, the phase during which two molecules of DNA are present in a chromosome is the G2 phase, as the DNA has been replicated but the cell has not yet divided.

### Final Answer:
The correct answer is **G2 phase**.

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