DNA Replication in the S Phase

Steps:

• Recall the cell cycle phases: interphase (G1, S, G2) and mitosis (M).
• Identify G1 as the initial growth phase where the cell prepares for DNA synthesis.
• Recognize S as the synthesis phase dedicated to duplicating DNA.
• Note G2 and M follow, focusing on preparation and division, not replication.

Why D is correct:

• The S phase is defined as the stage where DNA replication occurs to ensure each daughter cell receives a full genome copy.

Why the others are wrong:

• A. G1 involves cell growth and organelle synthesis, but no DNA replication.
• B. G2 is for growth and checkpoint verification after replication.
• C. M is mitosis, where the cell divides but does not replicate DNA.

Final answer: D