AP BIOLOGY

Detailed explanation-1: -There are three major checkpoints in the cell cycle: one near the end of G1, a second at the G2/M transition, and the third during metaphase.

Detailed explanation-2: -The G 1start subscript, 1, end subscript checkpoint is the main decision point for a cell – that is, the primary point at which it must choose whether or not to divide. Once the cell passes the G 1start subscript, 1, end subscript checkpoint and enters S phase, it becomes irreversibly committed to division.

Detailed explanation-3: -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.

Detailed explanation-4: -The cell will only pass the checkpoint if it is an appropriate size and has adequate energy reserves. At this point, the cell also checks for DNA damage. A cell that does not meet all the requirements will not progress to the S phase.

Detailed explanation-5: -The G2 checkpoint is used to prevent the cell from entering mitosis if there were errors in the replication of DNA during the S phase. Failure to pass the G2 checkpoint can result in apoptosis.