Cell Cycle POGIL Key

The Cell Cycle What controls the life and development of a cell? Why? An old piece of poetry says "to everything there is a season... a time to be born, a time to die." For cells, the line might say "a time to divide and a time to grow." In multicellular organisms, different types of cells have different roles and need to complete specific tasks. For example, a cell that isn't large enough is not useful for storing nutrients for later, but a cell that is too large will not be useful for transportation through a tiny capillary. In this activity, you will learn about the seasons of a cell's life, and in turn better understand how organisms function. Model 1 - The Cell Cycle G, Gap 1 M Mincluding cytokinesis) Go G22 S Synthesis 1. How many phases are in the cell cycle as shown in the diagram in Model 1? 4 2. Starting at the starred cell, what is the order of the stages of a cell's life? GSG₂→M 3. During which phase does the size of the cell increase? G 4. During which phase does the number of cells increase? M The Cell Cycle 5. Considering your answer to Questions 3 and 4, identify two ways that the growth of an organ-ism can be accomplished through the events of the cell cycle. 1. Cells can grow bigger 2. New, additional, cells can be made. 6. Cancer, the uncontrolled growth of cells, often results in a tumor, or mass of abnormal cells. Some cancerous tumors consist of many cells that are much smaller than normal. According to Model 1, what part(s) of the cell cycle is (are) most likely being affected? G, too short 7. In Model 1, if the length of the arrow represents time, then for those cancerous cells, what hap-pens to the time that is necessary for the cell cycle? What implication might this have for doctors who are treating cancer patients? Less time for cell cycle to be completed. Doctors may try to slow down cell cyde or kill rapidly dividing cells. Model 2-Cell Cycle Data Phase Key Process Time Interval (hours) 11 8 4 1 24 Sets of DNA present in each cell at end of phase 1 2 2 1 Number of organelles in each cell at end of phase Gap, Growth 560 Synthesis DNA replication 570 Gap, Protein and organelle synthesis 600 Mitosis 2 Cell and nuclear splitting 300 STOP Total time: 8. Model 2 presents cell cycle data for a typical human cell in culture. Use the phase names in Model 2 to label the G, M, and S phases in Model 1. 9. Looking at the third column of Model 2, compare the time spent in mitosis with the time spent in gap, in human cells and describe any difference. Gap 1 is llx longer than mitosis. POGIL Activities for High School Biology 10. Imagine 100 cells were chosen randomly from a tissue sample and examined under a microscope. In which phase of the cell cycle would you expect to find the largest number of cells? Explain. Most cells are in G,, since the largest fraction of the cell's life is spent in that phase. STOP 11. Look again at Model 2. Compare the amount of DNA at the beginning and end of synthesis. Why did the amount of DNA change? The amount of DNA doubled when the cell copied its DNA in s phase, so that each daughter cell would receive the correct 12. Fill in the "Key Process" column for synthesis phase in Model 2. amount of DNA. 13. Cytocell, kinesis cutting. What do you think takes place during cytokinesis? The cell splits (specifically the cytoplasm) 14. Other than cytokinesis, what else occurs during the mitosis phase? Hint: Consider the sets of DNA in each cell. The DNA is divided between two daughter cells. 15. Look carefully at information given to you in Model 1 and Model 2. Fill in the key process column in the table for gap, 16. If a culture in the lab starts with one human cell, how many cells will there be after 24 hours? 2 17. The total time for the phases listed in Model 2 is 24 hours. How many human cells will be in the culture after another 24 hours? Explain. 4. Each of the 2 cells mll split again. 18. Is the original cell "dead" or does it disappear after mitosis? Explain your answer. No. Its contents are split between the 2 daughter cells. 19. If a starfish sustains damage to a limb, it often grows a new one. If a human adult sustains damage to his or her spinal cord, mobility is often impaired. If a gecko loses its tail, it may grow a new one. Which type of cell is less likely to go through the cell cycle after being damaged-starfish limb, human spinal cord, or gecko tail? Support your answer. * Human spinal cord. The cells do not divide to heal the Camaged tissues. 20. Occasionally cells stop dividing and enter another phase, G. If you damage your liver, new liver Go non divi ding phase cells can be produced to replace up to 75% of the liver. However, if you sustain brain dam-age, your body does not produce new brain cells. Explain this observarion using what you have learned about the cell cycle. your brain cells are mostly in Go forever, but your liver cells mostly are not in Go. 3 The Cell Cycle