AP BIOLOGY

Detailed explanation-1: -The G1 checkpoint, also called the restriction point (in yeast), is a point at which the cell irreversibly commits to the cell division process. External influences, such as growth factors, play a large role in carrying the cell past the G1 checkpoint.

Detailed explanation-2: -At the G1 checkpoint, cells decide whether or not to proceed with division based on factors such as: Cell size. Nutrients.

Detailed explanation-3: -The decision to exit the cell cycle depends on just one of the cell cycle checkpoints – the DNA damage checkpoint (Box 2). Throughout interphase, in response to irreparable DNA damage, the DNA damage checkpoint can initiate quiescence, senescence or programmed cell death largely through p53-dependent pathways 103, 104.

Detailed explanation-4: -The G2 checkpoint ensures all of the chromosomes have been replicated and that the replicated DNA is not damaged before cell enters mitosis. The M checkpoint determines whether all the sister chromatids are correctly attached to the spindle microtubules before the cell enters the irreversible anaphase stage.

Detailed explanation-5: -Cell cycle checkpoints are surveillance mechanisms that monitor the order, integrity, and fidelity of the major events of the cell cycle. These include growth to the appropriate cell size, the replication and integrity of the chromosomes, and their accurate segregation at mitosis.