The DNA content of individual cells and the number of cells in each phase of a cell cycle" can be determined using flow cytometry. Which of the following combinations of "phase of a cell cycle and its corresponding DNA content" can be considered normal?
(i) Diploid cells found in the `G_(0)` or `G_(1)` phase.
(ii) Cells with twice the normal DNA content in the early M phase.
(iii) Cells with twice the normal DNA content in the `G_(2)` phase.

Options

A. i and ii
B. ii and iii
C. iii and iv
D. i,ii,iii and iv

Answer

To determine which combinations of the "phase of a cell cycle and its corresponding DNA content" can be considered normal, we need to analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Understanding DNA Content in Cell Cycle Phases**:
- The cell cycle consists of several phases: G1, S, G2, and M (which includes prophase, metaphase, anaphase, and telophase).
- DNA content is measured in picograms (pg). A diploid cell typically has 2 pg of DNA in G1 phase.

2. **Analyzing Statement (i)**:
- **Statement**: Diploid cells found in the G0 or G1 phase.
- **Analysis**: In the G1 phase, diploid cells indeed have 2 pg of DNA. In the G0 phase, cells are in a resting state but can still be diploid. Therefore, this statement is correct.

3. **Analyzing Statement (ii)**:
- **Statement**: Cells with twice the normal DNA content in the early M phase.
- **Analysis**: During the early M phase (specifically prophase and metaphase), the DNA content is indeed doubled (4 pg) due to DNA replication that occurs in the S phase. Thus, this statement is also correct.

4. **Analyzing Statement (iii)**:
- **Statement**: Cells with twice the normal DNA content in the G2 phase.
- **Analysis**: After DNA replication in the S phase, cells in the G2 phase also contain 4 pg of DNA. Therefore, this statement is correct as well.

5. **Conclusion**:
- All three statements (i, ii, and iii) are correct regarding the normal combinations of the phase of the cell cycle and their corresponding DNA content.

### Final Answer:
All three combinations are considered normal:
- (i) Diploid cells found in the G0 or G1 phase.
- (ii) Cells with twice the normal DNA content in the early M phase.
- (iii) Cells with twice the normal DNA content in the G2 phase.