Protecting Cell Integrity: Understanding the Checkpoints

Which checkpoint ensures cell growth before DNA replication?

A) G1 checkpoint

B) S checkpoint

C) G2 checkpoint

D) M checkpoint

Final answer:

The G1 checkpoint is responsible for ensuring that the cell is appropriately grown and prepared before DNA is replicated.

Explanation: The checkpoint that ensures the cell has adequate growth before DNA replication is the G1 checkpoint. As cells approach the transition from G1 to the S phase, this checkpoint assesses whether cells have attained sufficient size and have the necessary resources for DNA synthesis. The G1 checkpoint functions as a critical decision-making point where the cell commits to division only if all conditions are favorable, including checking for damage to the genomic DNA and ensuring adequate reserves and cell size. If the checkpoint conditions are not met, the cell enters a resting phase known as G0 until it is ready to proceed.

By contrast, the S checkpoint is responsible for confirming that DNA has been accurately replicated and is error-free. The G2 checkpoint evaluates whether DNA synthesis has been properly completed and whether the cell has all it needs to proceed into mitosis. The M checkpoint, or spindle checkpoint, ensures that all chromosomes are properly aligned before the cell proceeds with division. Each of these checkpoints plays a critical role in maintaining genomic integrity and preventing the propagation of errors during cell division.