For a somatic cell with 2n = 4 which of the following is true ?
Note :- `G_1` -growth phase 1, `G_2` - growth phase 2, M - Metaphase , P - Prophase and T - Telophase)

Options

A. Number of chromatids in `G_2` = 4 , Number of chromosome in `G_1` = 4
B. Number of chromatids in `G_1` = 8 , Number of chromatids in T= 8
C. Number of chromatids in P = 8 , Number of chromosomes in `G _2` = 4
D. Number of chromatids in `G_2` = 4 , Number of chromosomes in M = 8

Answer

To solve the question regarding a somatic cell with 2n = 4, we need to analyze the phases of the cell cycle and the number of chromosomes and chromatids present in each phase.

### Step-by-Step Solution:

1. **Understanding 2n = 4**:
- In this context, "2n" refers to the diploid number of chromosomes. Therefore, this somatic cell has a total of 4 chromosomes.

2. **Identifying Chromosome and Chromatid Numbers in Different Phases**:
- **G1 Phase**:
- In the G1 phase, the cell has not yet replicated its DNA. Therefore, the number of chromosomes is 4 (2n = 4), and since each chromosome is a single chromatid, the number of chromatids is also 4.
- **S Phase**:
- During the S phase, DNA replication occurs. Each chromosome is duplicated, resulting in 4 chromosomes (still 2n = 4) but now each chromosome consists of 2 sister chromatids. Thus, the total number of chromatids becomes 8.
- **G2 Phase**:
- In the G2 phase, the cell still has 4 chromosomes (2n = 4), but each chromosome consists of 2 sister chromatids, leading to a total of 8 chromatids.
- **Prophase**:
- In prophase, the cell is preparing for mitosis. The number of chromosomes remains 4, but they are now visible as 8 chromatids.
- **Metaphase**:
- During metaphase, the chromosomes align at the metaphase plate. The number of chromosomes is still 4, but they are represented as 8 chromatids.
- **Telophase**:
- In telophase, the chromosomes begin to de-condense. The number of chromosomes is still 4, and since the chromatids separate during anaphase, the number of chromatids will revert back to 4.

3. **Evaluating the Options**:
- **Option 1**: Number of chromatids in G2 = 8, Number of chromosomes in G1 = 4 (True)
- **Option 2**: Number of chromatids in G1 = 4, Number of chromatids in telophase = 4 (True)
- **Option 3**: Number of chromatids in prophase = 8, Number of chromosomes in G2 = 4 (True)
- **Option 4**: Number of chromatids in G2 = 8, Number of chromosomes in metaphase = 4 (False)

4. **Conclusion**:
- The correct statement is that the number of chromatids in prophase is 8, while the number of chromosomes in G2 is 4. Therefore, the correct answer is **Option 3**.