Find the correct statements with respect to replication of DNA in cell division

Options

A. It occurs during `G_(1)`-phase of interphase
B. New strands complimentary to old strands are synthesized with the help of endo-nucleases
C. Two strands of DNA unwind from each other due to DNA polymerase
D. It occurs by semi-conservation method

Answer

To find the correct statements regarding the replication of DNA in cell division, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Cell Cycle:**
- The cell cycle consists of two main phases: Interphase and the M phase (mitotic phase).
- Interphase is further divided into three stages: G1 phase, S phase, and G2 phase.
- The S phase is specifically where DNA replication occurs.

**Hint:** Remember the phases of the cell cycle and where DNA replication takes place.

2. **Analyzing the Options:**
- **Option 1:** "It occurs during G1 phase of interphase."
- This statement is **incorrect**. DNA replication occurs during the S phase, not the G1 phase.

**Hint:** Recall that G1 is primarily for cell growth and preparation for DNA synthesis.

- **Option 2:** "New strands complementary to old strands are synthesized with the help of endonucleases."
- This statement is **incorrect**. DNA replication involves the enzyme DNA polymerase for synthesizing new strands, not endonucleases.

**Hint:** Focus on the role of DNA polymerase in DNA replication.

- **Option 3:** "Two strands of DNA unwind from each other due to DNA polymerase."
- This statement is **incorrect**. The unwinding of DNA strands is facilitated by the enzyme helicase, not DNA polymerase.

**Hint:** Remember the function of helicase in the DNA replication process.

- **Option 4:** "It occurs by semi-conservative method."
- This statement is **correct**. In semi-conservative replication, each new DNA double helix consists of one old strand and one newly synthesized strand.

**Hint:** Understand the concept of semi-conservative replication and how it preserves genetic information.

3. **Conclusion:**
- The only correct statement regarding the replication of DNA in cell division is that it occurs by the semi-conservative method.

### Final Answer:
The correct statement is: **It occurs by semi-conservative method.**