AP BIOLOGY

Detailed explanation-1: -If the checkpoint mechanisms detect problems with the DNA, the cell cycle is halted, and the cell attempts to either complete DNA replication or repair the damaged DNA. If the damage is irreparable, the cell may undergo apoptosis, or programmed cell death 2.

Detailed explanation-2: -If the cell cycle checkpoints fail, cells that are not replicating correctly will be allowed to continue to grow and multiply. This is dangerous because the cell cycle mutations that are causing the failure can be passed on through the cell lineage.

Detailed explanation-3: -The DNA damage checkpoint provides the cell with an opportunity to stall cell division such that an effective DNA repair effort can be mounted. Blocking cells prior to mitosis prevents cells from transmitting broken chromosomes to a daughter cell and from losing acentric chromosome fragments.

Detailed explanation-4: -The G2 Checkpoint As at the G1 checkpoint, cell size and protein reserves are assessed. However, the most important role of the G2 checkpoint is to ensure that all of the chromosomes have been replicated and that the replicated DNA is not damaged.

Detailed explanation-5: -The G2/M checkpoint This checkpoint is operational in late G2 phase and presumably allows for repair of DNA that was damaged in late S or in the G2 phases of cell cycle prior to mitosis. Thus, the G2 checkpoint functions to prevent damaged DNA being segregated into daughter cells.