During which phase of the eukaryotic cell cycle does DNA replication occur?

• A. G1 phase of interphase
• B. S phase (synthesis) of interphase
• C. M phase (mitosis)
• D. G2 phase of interphase

Answer: (B)

Verified step by step guidance

1. Understand the phases of the eukaryotic cell cycle: G1 phase, S phase, G2 phase (all part of interphase), and M phase (mitosis).
2. Recall that DNA replication is the process of copying the cell's DNA to ensure each daughter cell receives an identical set of chromosomes.
3. Identify that DNA replication must occur before mitosis so that the chromosomes can be properly divided between daughter cells.
4. Recognize that the S phase (synthesis phase) of interphase is specifically dedicated to DNA replication.
5. Conclude that DNA replication occurs during the S phase of interphase, not during G1, G2, or M phases.