Which of the following checkpoint is predominantly activated when the DNA has started forming replication fork?

Step-by-step solution

There are three known checkpoints: the G 1 checkpoint, also known as the restriction or start checkpoint or major checkpoint; the G 2 /M checkpoint; and the metaphase checkpoint, also known as the spindle checkpoint. The primary G 1 /S cell cycle checkpoint controls the commitment of eukaryotic cells to transition through the G 1 phase to enter into the DNA synthesis in S phase