Which of the following activities occurs between the two gap phases (G1 and G2) of the cell cycle?

• A. DNA replication (S phase)
• B. Cytokinesis
• C. Spindle fiber formation
• D. Chromosome condensation

Answer: (A)

Verified step by step guidance

1. Understand the cell cycle: The cell cycle consists of several phases, including G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis). The G1 and G2 phases are gap phases where the cell grows and prepares for division, while the S phase is where DNA replication occurs.
2. Identify the activity that occurs between G1 and G2: The S phase is the phase that occurs between G1 and G2. During this phase, the cell replicates its DNA to ensure that each daughter cell will have a complete set of genetic material after division.
3. Clarify the other options: Cytokinesis occurs after mitosis during the M phase, not between G1 and G2. Spindle fiber formation and chromosome condensation are part of the M phase, specifically during mitosis, not during the S phase.
4. Focus on DNA replication: DNA replication is the key activity of the S phase. During this process, the cell duplicates its DNA using enzymes like DNA polymerase, ensuring that each chromosome is copied accurately.
5. Conclude the correct answer: Based on the cell cycle phases, the activity that occurs between G1 and G2 is DNA replication during the S phase.