Which of the following statements is correct with respect to cell cycle?

Options

A. A cell in G1 phase has double the amount of DNA than a cell in G2 phase
B. Each chromosome has two chromatids in G1 phase
C. Nerve cells in adult human are in GO state
D. DNA content of cell remains constant during entire cell cycle

Answer

To determine which statement is correct with respect to the cell cycle, we need to analyze each of the provided statements based on our understanding of the cell cycle phases.

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**: The cell cycle consists of two main phases: Interphase and Mitotic Phase (M phase). Interphase includes three sub-phases: G1 (first gap), S (synthesis), and G2 (second gap).

2. **G1 Phase**: In the G1 phase, the cell grows and synthesizes proteins. At this stage, the DNA content is at its original amount (for example, 46 chromosomes in humans).

3. **S Phase**: During the S phase, DNA replication occurs. Each chromosome is duplicated, resulting in two sister chromatids for each chromosome, which remain attached at the centromere.

4. **G2 Phase**: In the G2 phase, the cell continues to grow and prepares for mitosis. The DNA content is now doubled compared to G1 because of the replication that occurred during the S phase.

5. **G0 Phase**: Some cells enter a resting state known as G0, where they are metabolically active but not dividing. This is common in nerve cells of adult humans.

6. **Evaluating the Statements**:
- **Statement 1**: "A cell in G1 phase has doubled the amount of DNA than a cell in G2 phase." - This is incorrect. The G1 phase has less DNA than G2.
- **Statement 2**: "Each chromosome has two chromatids in G1 phase." - This is also incorrect. Chromatids are formed only after the S phase.
- **Statement 3**: "Nerve cells in adult humans are in G0 stage." - This is correct. Nerve cells typically remain in G0 and do not divide.
- **Statement 4**: "DNA content of the cell remains constant during the entire cell cycle." - This is incorrect. DNA content changes during the S phase and G2 phase.

7. **Conclusion**: The correct statement with respect to the cell cycle is that "nerve cells in adult humans are in G0 stage."