PATHOLOGY

Detailed explanation-1: -G1 checkpoint is also known as the restriction point at which the cell irreversibly commits to the cell division process. Cell set up certain requirements to be fulfilled by the cell to pass the check points. External factor such as growth factors play a vital role in carrying the cell past the G1 checkpoint.

Detailed explanation-2: -G2/M checkpoints include the checks for damaged DNA, unreplicated DNA, and checks that ensure that the genome is replicated once and only once per cell cycle. If cells pass these checkpoints, they follow normal transition to the M phase.

Detailed explanation-3: -The G1 checkpoint, just before entry into S phase, makes the key decision of whether the cell should divide.

Detailed explanation-4: -The point at G1 at which commitment occurs and the cell no longer requires growth factors to complete the cell cycle has been termed the restriction (R) point. The R point has been temporally mapped at 2–3 hours prior to the onset of DNA synthesis.