When cell has stalled DNA replication fork, which checkpoint should be predominantly activated?
Answer: (A) G1 / S. Answer: G1 / S Solution: A stalled DNA replication fork is a problem of incomplete/erroneous replication, which is monitored by the checkpoint guarding entry from G1 into S phase (the DNA-integrity/replication checkpoint), so the G1/S checkpoint is predominantly activated to halt the cycle before more damage propagates.
- A.G1 / S✓
- B.G2 / M
- C.M
- D.Both G2 / M and M
Correct Answer
(A) G1 / S
Solution & Explanation
Answer: G1 / S Solution: A stalled DNA replication fork is a problem of incomplete/erroneous replication, which is monitored by the checkpoint guarding entry from G1 into S phase (the DNA-integrity/replication checkpoint), so the G1/S checkpoint is predominantly activated to halt the cycle before more damage propagates. The G2/M and M (spindle) checkpoints act later, verifying that replication is finished and that chromosomes are correctly attached to the spindle, so they are not the primary responders to a stalled fork. (Specific cell-cycle checkpoints are a NEET extension beyond the NCERT chapter text, which describes S phase as the DNA-replication stage.) NCERT Reference: Ch 10, p.121, line 40 — "DNA synthesis or replication takes place"