THE EUKARYOTIC CELL CYCLE AND CANCER: AN OVERVIEW ABOUT THIS WORKSHEET This worksheet complements the Click and Learn “The Eukaryotic Cell Cycle and Cancerâ€� and is intended as a straightforward introduction to the cell cycle and how that relates to cancer. For a more comprehensive student worksheet, please see the in depth version. PROCEDURE Read through the Click and Learn at (http://www.hhmi.org/biointeractive/eukaryotic-cell-cycle-andcancer) to learn about the cell cycle. Answer the questions below. Click on the “Backgroundâ€� tab on the right side. Read the information and watch the videos. 1. Why is cell division important for both unicellular and multicellular organisms? Cell division is the only way for unicellular organisms to replace its old cell. Multicellular organisms need to grow using mitosis. 2. Why does cell division remain important to an adult organism even after it is fully developed? Cell division is still important to renew cells in organs and also heal cuts and broken bones. 3. Cells divide, differentiate, or die. What is differentiation? when cells are just functioning and carrying out their duties 4. What is apoptosis? What is its purpose? Apoptosis is eliminating uneeded cells 5. What are cell cycle regulators? They trigger or halt cell devision 6. What happens if cell cycle regulators don’t function properly? Cells can begin dividing too rapidly www.BioInteractive.org Published February 2016 Page 1 of 4 Click on the purple section labeled “Cell Cycle Phasesâ€� as well as the words “Mitosisâ€� and “Interphaseâ€� to read an overview of the cell cycle. You can also click on the various phases. Mitosis 7. Cells go through periods of growth and division. Cell division occurs during _______________. 8. The rest of the cell cycle is called interphase, during which _____________________________ Cells are just carrying out their functions _____________________________________________________________________________. 9. Fill in the details about what happens during the three phases of interphase labeled in the diagram. First gap phase Synthesis Phase Second gap phase 10. In general, what is the purpose of a checkpoint in the cell cycle? To make sure DNA is replicating correctly www.BioInteractive.org Published February 2016 Page 2 of 4 11. What is the G0 phase of the cell cycle? Which factors determine whether a cell enters G0? Can cells leave G0? G0 is not undergoing mitosis if it is lacking nutrients. no Click on “Cell Cycle Regulators and Cancerâ€� in the center purple circle. Read the Regulators Overview and then read through the Cancer Overview and watch the videos. 12. What are cell cycle regulators? proteins that control and regulate the cell cycle proto enconcogenes a. Stimulatory proteins are encoded by _________________________________. CDK cyclins Examples include: ______________________________________________________ tumor supressor genes b. Inhibitory proteins are encoded by ___________________________________________. P53 Examples include: ______________________________________________________ 13. Cancer is the result of an improperly regulated cell cycle. Describe two reasons why cells can form tumors. Cells replicate too rapidly creating tumors 14. In some types of colon cancer, stem cells have a mutation in the APC gene. What happens if the APC gene is mutated? If the APC gene is mutated, cell growth and division cannot be halted causing tumors to form 15. Normally, proto-oncogenes stimulate the cell cycle. What are oncogenes and how do they affect the cell cycle? Oncogenes can increase cell division rapidly, increasing stimulation www.BioInteractive.org Published February 2016 Page 3 of 4 1 a. To cause cancer, proto-oncogenes require _________ allele(s) to be mutated and dominant gain therefore are considered ____________________. The mutation results in a __________ of function. 16. Normally, tumor suppressor genes inhibit the cell cycle. How do mutated tumor suppressor genes affect the cell cycle? When mutated, tumor suppressor genes cause a lack of cell division both a. To cause cancer, tumor suppressor genes require _________ allele(s) to be mutated and recessive loss therefore are considered ____________________. The mutation results in a __________ of function. www.BioInteractive.org Published February 2016 Page 4 of 4 …
The Correct Answer and Explanation is :
Here are the answers with explanations to your questions based on the “Eukaryotic Cell Cycle and Cancer” worksheet:
1. Why is cell division important for both unicellular and multicellular organisms?
- Answer: Cell division is critical for unicellular organisms to reproduce and for multicellular organisms to grow, repair tissues, and replace damaged or dead cells.
2. Why does cell division remain important to an adult organism even after it is fully developed?
- Answer: Even in fully developed organisms, cell division is important for maintaining and renewing tissues and for healing injuries such as cuts or broken bones.
3. Cells divide, differentiate, or die. What is differentiation?
- Answer: Differentiation is the process by which cells become specialized to perform specific functions. For example, muscle cells differentiate to contract, and skin cells differentiate to form protective barriers.
4. What is apoptosis? What is its purpose?
- Answer: Apoptosis is the process of programmed cell death. It serves to eliminate damaged, unwanted, or unnecessary cells, thus preventing problems like cancer.
5. What are cell cycle regulators?
- Answer: Cell cycle regulators are proteins that control and coordinate the stages of the cell cycle, ensuring proper cell division. These include stimulatory proteins (e.g., cyclins, CDKs) and inhibitory proteins (e.g., tumor suppressor genes).
6. What happens if cell cycle regulators don’t function properly?
- Answer: If cell cycle regulators fail, cells may divide uncontrollably, leading to conditions like cancer. This can result in tumors forming due to rapid, unregulated cell growth.
7. Cells go through periods of growth and division. Cell division occurs during ___.
- Answer: Mitosis.
8. The rest of the cell cycle is called interphase, during which _________________.
- Answer: Cells carry out their normal functions, preparing for mitosis.
9. Fill in the details about what happens during the three phases of interphase:
- First gap phase (G1): The cell grows and carries out normal metabolic functions.
- Synthesis phase (S): DNA is replicated.
- Second gap phase (G2): The cell continues to grow and prepares for mitosis.
10. What is the purpose of a checkpoint in the cell cycle?
- Answer: Checkpoints ensure that DNA is replicated correctly and that the cell cycle progresses only when the conditions are right, preventing errors.
11. What is the G0 phase of the cell cycle? Which factors determine whether a cell enters G0? Can cells leave G0?
- Answer: The G0 phase is a resting or quiescent phase where cells do not divide. Cells enter G0 due to lack of nutrients or signals to divide. Some cells can leave G0 if they receive a signal to re-enter the cell cycle.
12. What are cell cycle regulators? Proteins that control and regulate the cell cycle proto-oncogenes?
- Answer: Stimulatory proteins are encoded by proto-oncogenes. Examples include cyclins and CDKs. Inhibitory proteins are encoded by tumor suppressor genes. Examples include p53.
13. Cancer is the result of an improperly regulated cell cycle. Describe two reasons why cells can form tumors.
- Answer: Tumors can form when cells replicate too quickly due to malfunctioning regulators, or when inhibitory proteins fail to stop abnormal cell division.
14. In some types of colon cancer, stem cells have a mutation in the APC gene. What happens if the APC gene is mutated?
- Answer: Mutation of the APC gene prevents proper regulation of cell growth and division, leading to uncontrolled cell proliferation and the formation of tumors.
15. Normally, proto-oncogenes stimulate the cell cycle. What are oncogenes and how do they affect the cell cycle?
- Answer: Oncogenes are mutated proto-oncogenes that cause the cell cycle to progress uncontrollably, leading to excessive cell division and potentially cancer.
16. Normally, tumor suppressor genes inhibit the cell cycle. How do mutated tumor suppressor genes affect the cell cycle?
- Answer: Mutated tumor suppressor genes fail to regulate or stop the cell cycle properly, leading to uncontrolled cell division.
- a. To cause cancer, proto-oncogenes require one mutated allele and are considered dominant gain-of-function mutations.
- b. To cause cancer, tumor suppressor genes require two mutated alleles and are considered recessive loss-of-function mutations.
Explanation:
The cell cycle is a highly regulated process that ensures proper growth, division, and differentiation of cells. Disruptions to this regulation can lead to uncontrolled cell growth, a hallmark of cancer. Tumor suppressor genes and proto-oncogenes are key players in regulating the cycle. Tumor suppressor genes like p53 inhibit cell division to prevent uncontrolled growth, whereas proto-oncogenes promote it. Mutations in these genes, whether gain-of-function in proto-oncogenes or loss-of-function in tumor suppressor genes, can result in cancer.