PATHOLOGY

Detailed explanation-1: -During division, the cell undergoes 4 distinct stages termed G1, S, G2, and M (mitosis). These periods of activity are separated by regulatory checkpoints at major transition phases. These checkpoints include G0/G1 which regulates the entry of a quiescent cell back into the cycle, G1/S, and G2/M.

Detailed explanation-2: -Cell-cycle checkpoints prevent the transmission of genetic errors to daughter cells. There exist three major cell-cycle checkpoints; the G1/S checkpoint, the G2/M checkpoint, and the spindle assembly checkpoint (SAC).

Detailed explanation-3: -The main cell cycle checkpoints are the G1/S checkpoint, the intra-S checkpoint, and the G2/M checkpoint [60]. The transition through stages of the cell cycle is regulated by the action of cyclin-dependent kinases, which are key targets for modulations induced by different cellular stimuli, including DNA damage.

Detailed explanation-4: -The G1 checkpoint. The G1 checkpoint is located at the end of G1 phase, before the transition to S phase. If cells don’t pass the G1 checkpoint, they may “loop out” of the cell cycle and into a resting state called G0, from which they may subsequently re-enter G1 under the appropriate conditions.