The amount of DNA in a cell in `G_(1)` phase is

Options

A. Half that of S-phase
B. Half that of `G_(2)` phase
C. Half that of prophase
D. All

Answer

To determine the amount of DNA in a cell during the G1 phase, we need to understand the cell cycle and the changes in DNA content that occur during its different phases. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding the Cell Cycle**:
- The cell cycle consists of a series of events that lead to cell growth and division. It includes two main phases: Interphase (which is the longest phase) and the M phase (mitotic phase).

**Hint**: Remember that the cell cycle is divided into phases, and Interphase is where most of the cell's growth and preparation for division occurs.

2. **Phases of Interphase**:
- Interphase is further divided into three sub-phases: G1 phase, S phase, and G2 phase.
- G1 phase is the first gap phase where the cell grows and synthesizes proteins.
- S phase is where DNA replication occurs, doubling the amount of DNA.
- G2 phase is the second gap phase where the cell prepares for mitosis.

**Hint**: Focus on the activities that occur in each phase to understand how DNA content changes.

3. **DNA Content in G1 Phase**:
- In G1 phase, if the cell is diploid (2n), the amount of DNA is represented as 2c, where "c" refers to the amount of DNA in a haploid cell.
- This means that in G1 phase, the DNA content is at its original state before replication.

**Hint**: Recall that "c" represents the basic unit of DNA content, and "2c" indicates that there are two sets of chromosomes.

4. **DNA Content in S Phase**:
- During the S phase, DNA replication occurs, and the amount of DNA doubles from 2c to 4c.

**Hint**: Remember that S phase is crucial for DNA replication, leading to an increase in DNA content.

5. **DNA Content in G2 Phase**:
- After S phase, in G2 phase, the DNA remains at 4c until the cell divides.

**Hint**: G2 phase is where the cell has completed DNA replication and is preparing for mitosis.

6. **Comparing DNA Content**:
- Given the options:
- Half that of S phase: **Not true** because S phase has 4c.
- Half that of G2 phase: **True** because G2 has 4c, and G1 has 2c.
- Half that of prophase: **True** because prophase also has 4c.
- All of the above: **Not correct**, as only two statements are true.

**Hint**: Analyze each option carefully by comparing the DNA content in each phase.

### Conclusion:
The amount of DNA in a cell in the G1 phase is **2c**, which is half that of G2 phase (4c) and half that of prophase (4c). Therefore, the correct answers are:
- Half that of G2 phase
- Half that of prophase