If the number of chromosomes in `G_(1)` phase is 18. What will be the number of chromosomes in S-phase.

Options

A. 36
B. 18
C. 9
D. 19

Answer

To determine the number of chromosomes in the S-phase given that the number of chromosomes in the G1 phase is 18, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Phases of the Cell Cycle**:
- The cell cycle consists of several phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis).
- G1 is the first phase where the cell grows and prepares for DNA synthesis.
- S-phase is where DNA replication occurs.

2. **Identify the Number of Chromosomes in G1 Phase**:
- According to the question, the number of chromosomes in the G1 phase is given as 18.

3. **Analyze the S-phase**:
- During the S-phase, the cell replicates its DNA. This means that each chromosome is duplicated.
- However, the number of distinct chromosomes does not change during the S-phase; rather, the amount of DNA doubles.

4. **Determine the Number of Chromosomes in S-phase**:
- Since the number of distinct chromosomes remains the same during the S-phase, the number of chromosomes in the S-phase will also be 18.

5. **Conclusion**:
- Therefore, the number of chromosomes in the S-phase is 18.

### Final Answer:
The number of chromosomes in the S-phase is **18**.

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