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

Options

A. DNA content of cell remains constant during entire cell cycle
B. A cell in `G_(1)` phase has double the amount of DNA than a cell in `G_(2)` phase
C. Each chromosome has two chromatids in `G_(1)` phase
D. Nerve cells in adult human are in `G_(0)` state

Answer

To determine which statement is correct with respect to the cell cycle, let's analyze each of the provided statements step by step.

### Step-by-Step Solution:

1. **Statement 1: The DNA content of the cell remains constant during the entire cell cycle.**
- This statement is **incorrect**. The DNA content changes during the cell cycle. For instance, during the S phase (synthesis phase), DNA is replicated, leading to a doubling of the DNA content. In mitosis, the DNA is divided equally between two daughter cells, and in meiosis, the DNA content is halved.

2. **Statement 2: A cell in G1 phase has double the amount of DNA than a cell in G2 phase.**
- This statement is also **incorrect**. In the G1 phase, the cell has a single set of chromosomes (2n), while in the G2 phase, the cell has already replicated its DNA and contains double the amount of DNA (4n). Therefore, a cell in G1 does not have double the DNA compared to a cell in G2; it has half.

3. **Statement 3: Each chromosome has two chromatids in G1 phase.**
- This statement is **incorrect**. In the G1 phase, each chromosome consists of a single chromatid. The formation of sister chromatids occurs during the S phase when DNA is replicated.

4. **Statement 4: Nerve cells in adult humans are in the G0 stage.**
- This statement is **correct**. Nerve cells (neurons) in adult humans typically enter the G0 phase, which is a resting state where they are not actively dividing. This is a characteristic of differentiated cells that do not undergo further division.

### Conclusion:
The correct statement with respect to the cell cycle is: **Nerve cells in adult humans are in the G0 stage.**