PATHOLOGY

Detailed explanation-1: -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-2: -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.

Detailed explanation-3: -1: Internal Checkpoints During the Cell Cycle: The cell cycle is controlled at three checkpoints. The integrity of the DNA is assessed at the G1 checkpoint. Proper chromosome duplication is assessed at the G2 checkpoint. Attachment of each kinetochore to a spindle fiber is assessed at the M checkpoint.

Detailed explanation-4: -Between G1 and S phase, three DNA damage checkpoints occur to ensure proper growth and synthesis of DNA prior to cell division. Damaged DNA during G1, before entry into S phase, and during S phase result in the expression of ATM/R protein.

Detailed explanation-5: -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.