Stalled forks activate checkpoint signaling and pause replication. Since G1/S checkpoint checks DNA damage, cells size prior to S-phase (i.e DNA replication phase). This checkpoint would be activated by stalled DNA replication fork.

So, correct answer is "G1/S"...

$$Hope it's help... $$

Which Checkpoint Should be Predominantly Activated in Stalled DNA Replication Fork?

Stalled DNA replication fork can occur due to various factors such as DNA damage, nucleotide depletion, or replication stress. To prevent the continuation of DNA replication in such situations, cells have evolved checkpoint mechanisms that help to preserve genomic integrity. The activation of checkpoints depends on the stage of the cell cycle and the type of DNA damage.

The checkpoints in the cell cycle are G1/S, G2/M, and spindle assembly checkpoint (SAC). The G1/S checkpoint monitors the integrity of DNA before the replication starts, the G2/M checkpoint ensures that DNA is properly replicated before entering mitosis, and the SAC checkpoint ensures the proper attachment of spindle fibers to chromosomes during mitosis.

Which checkpoint should be predominantly activated in stalled DNA replication fork?

The answer is (3) G2/M checkpoint. Here are the reasons:

1. G2/M checkpoint:
The G2/M checkpoint is activated when DNA replication is stalled due to various factors such as replication stress, DNA damage, or nucleotide depletion. The activation of the G2/M checkpoint prevents cells from entering mitosis until the DNA replication is complete or the damage is repaired.

2. Both G2/M and M checkpoint:
The M checkpoint is also activated in response to DNA damage or replication stress, but it occurs during mitosis. The M checkpoint ensures that chromosomes are properly aligned and attached to spindle fibers before they are separated during anaphase.

3. G1/S checkpoint:
The G1/S checkpoint monitors the integrity of DNA before the replication starts. If DNA damage is detected, the checkpoint activates the DNA repair mechanisms or triggers cell cycle arrest to prevent the replication of damaged DNA. However, if DNA replication is already initiated and stalled, the G1/S checkpoint is not activated as it is not designed to monitor ongoing replication.

In summary, the G2/M checkpoint should be predominantly activated in stalled DNA replication fork as it monitors DNA replication during the G2 phase and prevents cells from entering mitosis until DNA replication is complete or damage is repaired.