Cell A is actively engaging in growth and division. The cell encounters a damage in its DNA at acertain point in the cell cycle.What would be the reaction in the cells if the damage was sensedBefore the R point is passedAfter passing the R pointWhat would be the similarities and differences in the reaction in the cell in cases a and b?In your answer, briefly include the significance of the R point during the cell cycle

Introduction: The restriction point or R-point denotes the start of a cell cycle (G1/S phase). R-point is a checkpoint in G1-phase of the cell division cycle of the animal cell. At this point, the cell becomes committed to the cell cycle and after which no extracellular signals are required to stimulate proliferation.Explanation: Case a: If the damage is sensed in the DNA of a cell before the point is passed. A checkpoint is a primary point at which a cell chooses to divide or not. If any damage is sensed at R-point then the cell would choose to repair the damage before going to S-phase and if the damage is unable to be cured then the cell would prefer not to be processed further for division it will be restricted to G0-phase which is also known as resting phase. Explanation: case b: If damage is sensed after passing the R-point After passing the R-point, there is a second checkpoint in the process of cell division to make sure that the division is going smoothly to produce healthy daughter cells with complete undamaged DNA. if damage in the DNA is observed then the cell would allow repairing. but if the damage is irreparable then the cell would undergo apoptosis (programmed death of the cell ) to ensure that the damaged DNA should not transform to the daughter cells. So, R-point had a great role in the process of cell division. it provides healthy daughter cells and helps to prevent cancer and many other chromosomal diseases.