Question

The Phase in which two identical copies of DNA are formed is:

• A. \( \text{M phase} \)
• B. \( \text{G2 phase} \)
• C. \( \text{G1 phase} \)
• D. \( \text{S phase} \)

Hint:

The \( S \) phase is critical for genetic continuity during cell division. Errors in DNA replication during this phase can lead to mutations or chromosomal abnormalities.

Answer 1

The Correct Option is D

Step 1: Understanding the phases of the cell cycle. The cell cycle consists of the following phases: 
1. G1 phase: The cell grows and prepares for DNA replication. 
2. S phase: DNA replication occurs, resulting in the formation of two identical copies of DNA. 
3. G2 phase: The cell prepares for mitosis by synthesizing necessary proteins and organelles. 
4. M phase: The cell undergoes mitosis and cytokinesis, resulting in two daughter cells. 

Step 2: Explanation of DNA replication. During the \( S \) phase (synthesis phase), the DNA in the cell is duplicated, ensuring that each daughter cell receives an identical copy during cell division. 

Step 3: Comparison with other options. - Option \( (A) \): \( M \) phase is the mitotic phase where cell division occurs, not DNA replication. 
- Option \( (B) \): \( G2 \) phase is for cell growth and preparation for mitosis, not DNA synthesis. 
- Option \( (C) \): \( G1 \) phase is the initial growth phase before DNA replication. 

Conclusion: DNA replication occurs in the \( S \) phase, making \( (D) \) the correct answer.