<s>[INST] context: (G1 - S phase) (60-195- Basic pathology 8th)* The S phase is the point of no return in the cell cycle and before the cell makes the final commitment to replicate - the G1/S checkpoint checks for damage.* This causes delay at G1/S checkpointThis delay in cell cycle progression provides the time neededfor DNA repair and if the damage is not reparable, apoptoticpathways are activated to kill the cell.G2 M checkpoint* This check point in used for the repair of the DNA which is damaged after its replication* The G2M checkpoint monitors the completion of DNA replication and checks whether the cell can safely initiates mitosis and separate sister chromatids(i) This checkpoint is particularly important in cells exposed to ionizing radiations(ii) Defects in this check points give rise to chromosomal abnormalityAlso known Effector for G1S checkpoint - Mostly mediated through P53 which induces the cell cycle inhibitor P21 Effector for G2M checkpoint - Involves both P53 and independent mechanismCyclinKinaseFunctionsDCD4.CDK6Progression past restriction at G1S boundaryEl-ACDK-2Initiation of DNA synthesis in early S phaseBCDK-1Transition from G2 to M [/INST] question: The tumor suppressor gene P53 induces cell arrest at | options: A: G2- M phase B: S- G2 phase C: G1-S phase D: G0- phase | answer: C </s>