What does the G1 checkpoint in the cell cycle primarily monitor?

• A. Cell size and nutrient availability
• B. Spindle fiber attachment
• C. Chromosome alignment
• D. DNA damage

Answer: (D)

Verified step by step guidance

1. Understand the cell cycle: The cell cycle consists of several phases, including G1, S, G2, and M. Each phase has specific checkpoints to ensure the cell is ready to proceed to the next stage.
2. Focus on the G1 phase: The G1 phase is the first gap phase after cell division, where the cell grows and prepares for DNA replication. It is crucial for determining whether the cell is ready to enter the S phase.
3. Identify the G1 checkpoint: The G1 checkpoint is a control mechanism that ensures the cell is ready for DNA synthesis. It checks for factors that could affect the cell's ability to replicate DNA accurately.
4. Determine what the G1 checkpoint monitors: The G1 checkpoint primarily monitors cell size, nutrient availability, and DNA integrity. It ensures that the cell has sufficient resources and is free from DNA damage before proceeding.
5. Clarify the role of DNA damage monitoring: DNA damage is a critical factor monitored at the G1 checkpoint. If DNA damage is detected, the cell cycle is halted to allow for repair, preventing the propagation of errors to daughter cells.