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Name _________________________________________ Cell Cycle and Cancer Name _________________________________________ Introduction Name _________________________________________ Model 1 – The Cell Cycle Date ___________________ Cell growth and division is a function that characterizes all living organisms. Looking at your own body, you can identify numerous examples of cell division occurring at this very moment! For example: Cell division of skin cells to replace those that have died and fallen off. Cell division in bone marrow to make red blood cells. Cell division of stomach cells to replace those that have been damaged due to exposure to the hydrochloric acid released into the stomach. These are just a few examples of the cell cycle in action. The cell cycle is a sequence of events that involve growth and division. The cell cycle is organized into two major parts; interphase and mitosis. Interphase is comprised of Gap1, DNA synthesis and Gap 2. When the cell is in interphase, it carries out normal metabolic activity, grows, and replicates its’ DNA so that both daughter cells have a copy of it. Mitosis follows interphase and is when the nucleus divides into two daughter nuclei. Following Mitosis the cytoplasm splits and the cell divides into two identical daughter cells in a process called Cytokinesis. Eukaryotic Cell Division 1. Which type of cell, prokaryotic or eukaryotic, does Model 1 apply to? 2. What stage(s) in the diagram represent growth phase(s) for the cell? 3. During which stage of the cell cycle is the genetic material duplicated? 4. Why must genetic material be duplicated (also known as replication or copying)? 5. What happens inside the cell during Mitosis (M)? (If you start with one nucleus, what do you end with?) 6. Which part of the process of cell division is not listed on the chart above? What happens during this process? Model 2: Mitosis During the Cell Cycle the majority of the time is spent in interphase (up to 90%). Mitosis follows Interphase and is defined as the process of producing two identical daughter cells from one parent cell. Mitosis follows a series of steps called the mitotic process. Those steps in order are Prophase, Metaphase, Anaphase and Telophase. Using your notes, look at each cell below and decide which stage of the Cell Cycle it is in. Your options are Interphase, Prophase, Metaphase, Anaphase and Telophase. Plant Cells in Mitosis Label the cells below: 1. 7. 13. 2. 8. 14. 3. 9. 15. 4. 10. 16. 5. 11. 17. 6. 12 18. 19. Count the number of cell’s that are in each phase and list the numbers below (make sure to label which phase). Prophase – During Prophase the chromatin condenses down to chromosomes. Also, the nuclear membrane and nucleolus disappear. Finally the centrosomes move apart from each other the spindle begins to form. Metaphase - During metaphase the chromosomes line up in the middle of the cell along the equator. The spindle attaches to the chromosomes at a spot called the centromere which is the middle of the chromosome. Anaphase – During Anaphase the chromosomes are pulled apart by the spindle. Each chromosome is made of two sister chromatids that are identical. In Anaphase the sister chromatids are split apart and move to opposite sides of the cell. Telophase – During Telophase the chromosomes are completely separated. The nuclear membrane and nucleolus reform and you are left with two nuclei. Mitosis is now complete. Stages of Mitosis Match each statement with the correct phase of mitosis or with the process of cytokinesis. A. Prophase B. Metaphase C. Anaphase D. Telophase E. Cytokinesis _______1. The phase during which the nuclear membrane reappears. _______2. The phase during which the spindle attaches to the centromere of each sister chromatid _______3. Cromatin (which is loose and thin) condenses down to solid chromosomes during this phase. _______4. The nuclear membrane disappears before this phase starts. _______5. During this phase the sister chromatids are separated and pulled away from each other _______6. During this phase the cell pinches together and splits the cytoplasm. _______7. Finally we see the beginning of two nuclei during this phase. _______8. During this phase all the chromosomes are lined up together in the middle of the cell. 9. The events of the cell cycle are coordinated by various proteins in the cell. These proteins are encoded by genes that are switched on and off in a highly controlled fashion. This ensures that the proteins required for G1 are only produced during G1 and that the proteins required for mitosis are only produced during mitosis. This allows multicellular organisms to precisely control when and where the cells in its body divide. Indiscriminant, constant cell division does not allow multicellular organisms to maintain specific form and functions of its tissues. Make a prediction as to what would occur if the genes for proteins that control when and where cells of your body divide were mutated (damaged)? Explain your thoughts. Model 3: Regulation of the Cell Cycle For many years, it was a mystery to scientists how cells controlled their cell division. Scientists now know that the cell cycle is highly regulated by checkpoints that control cell growth and division. These checkpoints can stop the cell cycle and prevent it from dividing when it would be harmful to the organism. When the chemical signals controlling this process fail, very bad things start happening. Part 1 Oncogenes: The bad guys, turn abnormal cell growth on (go/gas pedal) An oncogene is a gene that has been mutated in a way that leads to signals that cause uncontrolled growth- i.e., cancer. This is like pushing down on a car’s gas pedal- you now have a gene that is telling the cell to "go, go, go!” and never stop. Part 2 Tumor suppressor genes: The good guys gone bad Tumor suppressor genes in normal cells act as braking signals during phase G1 of the cell cycle, to stop or slow the cell cycle before S phase. If tumor-suppressor genes are mutated, the normal brake mechanism will be disabled, resulting in uncontrolled growth, i.e. cancer. Oncogenes are mutated genes whose PRESENCE can stimulate the development of cancer. Tumor suppressor genes are normal genes whose ABSENCE can lead to cancer. 7. What are two types of genes that play a major role in regulating the cell cycle? Describe what effect the genes have on the regulation. 8. What would happen to a cell that experiences a mutation in a tumor-suppressor gene? What is Cancer? How does a cell “know” when it is time to divide? What controls these events to ensure that the division occurs properly and correctly? These are critical questions to scientists who study the cell cycle because not only do their answers provide insight into normal cell function, their answers help us better understand diseases that arise when the process goes awry. Figure A Figure B Normal Cells Have external growth factors to divide Contact inhibition – contact with other cells results in stop of cell division Age and die then replaced in controlled and orderly manner with limited number of divisions Cease to divide and die when there is DNA damage or when cell division is abnormal Cancer Cells Lost need for positive growth factors Continue to divide after contact Unlimited number of cell divisions Even with damage to DNA continue to divide even when large amount of damage to DNA or when the cell is abnormal 10. Cancer cells do not stop dividing. Which picture above demonstrates abnormal cell division? Why? 11. Using the information in Model 3 Table, describe three differences between the cells pictured in the diagrams A and B.