Which of the following correctly matches a phase of the cell cycle with a key event that occurs during that phase?

• A. S phase — DNA replication
• B. G1 phase — Chromosome segregation
• C. G2 phase — Cytokinesis
• D. M phase — Organelle duplication

Answer: (A)

Verified step by step guidance

1. Understand the cell cycle: The cell cycle is divided into interphase (G1, S, and G2 phases) and the mitotic phase (M phase). Each phase has specific events that occur to prepare the cell for division or to complete division.
2. Review the S phase: During the S phase (synthesis phase), DNA replication occurs. This is when the cell duplicates its genetic material to ensure that each daughter cell receives an identical copy of the DNA.
3. Review the G1 phase: The G1 phase (gap 1 phase) is a period of cell growth and preparation for DNA replication. Chromosome segregation does not occur in this phase; it happens during mitosis (M phase).
4. Review the G2 phase: The G2 phase (gap 2 phase) is a period of preparation for mitosis. The cell checks for DNA damage and ensures all necessary proteins for mitosis are present. Cytokinesis, the division of the cytoplasm, does not occur in this phase; it occurs after mitosis.
5. Review the M phase: The M phase (mitotic phase) includes mitosis and cytokinesis. Organelle duplication does not occur in this phase; it typically happens during interphase (G1 or S phase).