In eukaryotic cells, during which phase of the cell cycle does DNA replication occur?

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

Answer: (B)

Verified step by step guidance

1. Understand the phases of the eukaryotic cell cycle: G1 phase (first gap), S phase (synthesis), G2 phase (second gap), and M phase (mitosis).
2. Recall that DNA replication is the process of copying the entire genome to prepare for cell division.
3. Identify that DNA replication specifically occurs during the S phase, where the cell synthesizes a complete copy of its DNA.
4. Note that G1 and G2 phases are primarily for cell growth and preparation, while M phase is when the cell actually divides.
5. Conclude that the S phase of interphase is the correct phase during which DNA replication takes place.