If the cell had 4n number of chromosome at `G_(1)`, after s phase the number of chromosome in the cell will be :-

Options

A. 2n
B. n
C. 4n
D. 8n

Answer

To solve the question, "If the cell had 4n number of chromosomes at G1, after S phase the number of chromosomes in the cell will be:", we need to understand the cell cycle, particularly the G1 and S phases.

### Step-by-Step Solution:

1. **Understanding the G1 Phase**:
- In the G1 phase (Gap 1), the cell has a certain number of chromosomes. Here, it is given that the cell has 4n chromosomes. The "n" refers to the basic number of chromosomes in a haploid set, so 4n indicates that the cell is diploid with 4 sets of chromosomes.

2. **Understanding the S Phase**:
- The S phase (Synthesis phase) is when DNA replication occurs. During this phase, each chromosome is duplicated, resulting in two identical copies called sister chromatids. However, it is crucial to note that while the amount of DNA doubles, the number of chromosomes remains the same.

3. **Counting Chromosomes After S Phase**:
- Even though the DNA has been replicated and each chromosome now consists of two sister chromatids, the total number of chromosomes does not change. Therefore, if the cell had 4n chromosomes at the beginning of the S phase, it will still have 4n chromosomes after the S phase.

4. **Conclusion**:
- The number of chromosomes in the cell after the S phase remains 4n.

### Final Answer:
The number of chromosomes in the cell after S phase will be **4n**.

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