Question

BOL200, Exercise 18 1. What cellular conditions are assessed at each of the cell cycle control checkpoints? 61/5: The integrity of the DNA 62/M: Proper chromosome duplication M (Spindle): Attachment of each kinetochore to a spindle fiber 2. What would happen in each case below? Would the cell stop progression through the cell cycle, and if so, at what stage? Would the cell continue through the cell cycle? a. A mutation that prevents the synthesis of growth factor receptors b. A mutation that prevents repair of mistakes made during DNA synthesis. LA m io that prevents condensed omsomes from thing to the spindle apparatus A mutation that prevents tion of the Godin

Answer 1

11 Answer :- G-S Checkpoint (i) If the cell is large enough to divide w Whether the cell have enough nutrient - available to divide. como If any of the DNA is damaged. civ) I's the cell receiving positive molecular signals or not. Example: growth factors. If the cell can not clear all these checkpoints, it may enter the Go phase or resting phase, and if the cell clears it all then it will progress further G2-M Checkpoint (i) The cell again cheeks if any of the DNA damaged. If any error detected, the cell will stop at the G2 phase allowing itself to repair the damage [either by completing . DNA replication or by repairing the damage] ( It checks if the DNA was completely replicated during & phase on not . . When the damage is irrepairable, the cell may undergo self destruction mechanism also called a apoptosis

M Phase Checkpoint mosomes The M phase (mitotic phase) checkpoint is also called spindle checkpoint. Here the cell checks - S » If the sister chromatids are all correctly attached to spindle microtubule or not. All the chromosomes must attache to atleast two spindle fibre from each pole of that cell. Cell cheers is misplaced in the spindle or . .or not even placed in spindle i.e., floating in the cytoplason. . If the cell can not clear the pindle checkpoint, Then the cell cycle stops then and there allowing the spindle to correctly attach the chromosome

3 21 Answers I a. A mulation that prevents the synthesis of ... growth factor receptors - If this happens theor the cell will not get to the size that it should be. The growth factors works as a signal molecule that gives positive signals to cell to proceed through cell cycle. As the growth factor receptors are mutated, this will not happen Пою. Thus, the cell would stop progression through E cell cycle at the G, phase. The cell would not continue through the 3 cell cycle. 3 e b. A onutation that prevents repair of mistukes I made during DNA synthesis-' If this happens then the damaged DNA or the DNA with mistares can't be repaired. Thus, the cell may undergo self destruction mechanism i.e. a apopfteis. The cell would stop progression through cell cycle at the G2 phase. all the cell would not continue Shrough the e

. I c. A mutation that prevents chromosome in from attaching to the spindle apparatus. . It may result in nondisjunction. The cell would fail to separate chromosomes in two equal sets. Then it cytokinosis occurs, two cells with unequal chromosome sets would be produced. - As it is an irrevasible step, the cell cycle will not proceed untill all the chromosomes in the cell are correctly attached to the spindle. But, in this case mutation occurred which may result in nondisjunction wit cell cycle proceeds through it. - This will happen at the anaphase of cell cycle. I d. A mutation the prevents degradation of Gi cyclin. - Gi cyelin with not bec degraded and it can block the onetaphase-anaphase transition The cell would stop progression at metaphase.

11 Answer in G1 Checkpoint (i) If the cell is large enough to divide 4 Whether the cell have enough nutrient - available to divide. If any of the DNA is damaged. civ) I's the cell receiving positive molecular signals or not. Example: growth factors. If the cell can not clear all these checkpoints, it may enter the Go phase or resting phase, and if the cell clears it all then it will progress further G2 Checkpoint ( The cell again cheeks if any of the DNA damaged. If any error, detected, the cell will stop at the G2 phase allowing itself to repair the damage, Leither by completing DNA replication or by repairing the damage] It cheeks if the DNA was completely replicated during & phase or not. ( UI When the damage is irrepairable, the cell may undergo self destruction mechanism also called apoptosis.

M Phase Checkpoint ONO - The M phase Conitotic phase) checkpoint is also called spindle checkpoint. Here the cell checks - »'If the sister chromatids are all correctly attached to spindle microtubule or not. All the chromosomes must attache to atleast two spindle fibre from each pole of that cell. . Cell checks is misplaced in the spindle or ...or not even placed in spindle i.e., floating in the cytoplasm. If the cell can not clear the spindle checkpoint, Then the cell cycle stops then and Shere allowing the spindle to correctly attach the chromosome. Dlasa

golon À 21 Answers 3 a. A mutation that prevents the synthesis of growth factor receptors - If this happens theor the cell will not get to Stie size that it should be. The growth factors works as a signal molecule that gives positive signals to cell to proceed Shrough cell cycle. As the growth factor receptors are mutated, this will not happen now. . - Thus, the cell would stop progression through E celleycle at the G, phase. E The cell would not continue through the 3 cell cycle. 3. b. A mutation that prevents repair of mistures 6. made during DNA synthesis-' If this happens then the damaged DNA or the 3 DNA with mistares can't be repaired. Thus, the 3 cell nay undergo self destruction mechanism i.e. a apophtais. The cell would stop parogorusion through cell a cycle at the G2 phase o The cell would not continue through the a cell cycle.co

- c. A mutation that prevents chromosome in from attaching to the spindle apparatus. . It may result in nondisjunction. The cell would fail to separate chromosomes in two equal sets. Then it cytokinosis occurs, two cells with unequal chromosome sets would be produced. . As it is an irrevasible step, the cell cycle will not proceed untill all the chromosomes in the cell are correctly attached to the spindle But, in this case mutation occurred which may result in nondisjunction wit cell cycle proceeds through it. . This will happen at the anaphase of cell cycle. I d. . • I the A mutation the prevents degradation of Gi eyelin. Gi cyelin will not be deqraded and it can block onetaphase- anaphase transition The cell would stop progression at metaphase.