In a typical proliferating eukaryotic cell, which phase is generally the longest portion of the cell cycle?

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

Answer: (A)

Verified step by step guidance

1. Understand the cell cycle phases: The cell cycle consists of interphase (G1, S, G2 phases) and the M phase (mitosis and cytokinesis).
2. Recall the function of each phase: G1 phase is the first gap phase where the cell grows and prepares for DNA replication; S phase is when DNA synthesis occurs; G2 phase is the second gap phase where the cell prepares for mitosis; M phase is when mitosis and cytokinesis happen.
3. Consider the duration of each phase: In a typical proliferating eukaryotic cell, the G1 phase is usually the longest because the cell is metabolically active and growing, and it decides whether to proceed with division.
4. Compare the lengths of other phases: S phase and G2 phase are generally shorter because DNA replication and preparation for mitosis are more time-constrained processes, and M phase is the shortest as it involves actual cell division.
5. Conclude that the G1 phase is the longest portion of the cell cycle in a typical proliferating eukaryotic cell.