Which checkpoint verifies that DNA replication has occurred accurately before the cell enters mitosis?

Which checkpoint verifies that DNA replication has occurred accurately before the cell enters mitosis?

• A. G1 checkpoint
• B. G2 checkpoint
• C. M checkpoint
• D. S-phase checkpoint

Answer: (B)

Ensuring DNA replication is complete and accurate before mitosis is the role of the G2 checkpoint. After the DNA is replicated in the S phase, the cell uses this checkpoint to verify that all chromosomes have been fully duplicated and that any DNA damage has been repaired. If issues are detected, the cell pauses to fix them before entering mitosis, preventing chromosome missegregation. The S-phase checkpoint operates during replication to slow or stop replication when problems arise, but it focuses on ongoing DNA synthesis rather than confirming completion before mitosis. The M-phase checkpoint (spindle checkpoint) checks that chromosomes are properly attached to the spindle during metaphase, not replication fidelity. The G1 checkpoint assesses conditions to begin DNA replication, not after replication has occurred.

Ensuring DNA replication is complete and accurate before mitosis is the role of the G2 checkpoint. After the DNA is replicated in the S phase, the cell uses this checkpoint to verify that all chromosomes have been fully duplicated and that any DNA damage has been repaired. If issues are detected, the cell pauses to fix them before entering mitosis, preventing chromosome missegregation. The S-phase checkpoint operates during replication to slow or stop replication when problems arise, but it focuses on ongoing DNA synthesis rather than confirming completion before mitosis. The M-phase checkpoint (spindle checkpoint) checks that chromosomes are properly attached to the spindle during metaphase, not replication fidelity. The G1 checkpoint assesses conditions to begin DNA replication, not after replication has occurred.