Cell Cycle and Cancer Overview

The Eukaryotic Cell Cycle and Cancer Overview INTRODUCTION This handout complements the Click & Learn The Eukaryotic Cell Cycle and Cancer and is intended as a straightforward introduction to the cell cycle and how it relates to cancer. For a more comprehensive student handout, please see the in-depth version. PROCEDURE Follow the instructions as you proceed through the Click & Learn and answer the questions in the spaces below. Click on the “Background” tab on the right side. Read the information and watch the videos. 1. Why is cell division important for both single-celled and multicellular organisms? For single-celled organisms division is important because it is their only mode of reproduction, thus they need it to prevent extinction. For Multicellular organisms, cell division is used as a growth mechanism and to replace old and dead cells, allowing the organism to function. 2. Why does cell division remain important to an adult organism even after it is fully developed? For an adult organism, cell division remains essential because it can allow for replacement of dead cells and can help heal wounds and mend broken bones. It is a basic function in humans to have cell turnover so that our organs remain efficient and functional. 3. What is the role of growth factors? Growth factors give signals to cells in order to make them divide. Without these factors there would be no cell division. 4. Cells divide, differentiate, or die. What is differentiation? Differentiation is when a cell stops dividing in order to specialize in a particular function, also changing their structure as a result. 5. What is apoptosis? What is its purpose? Apoptosis is used to eliminate unnecessary, damaged, or unhealthy cells through what is in essence a programmed death for the cell. 6. What are cell cycle regulators? They function as molecular signals to initiate cell death, prompt or cease cell division, or direct cells to undergo differentiation. 7. What happens if cell cycle regulators don’t function properly? Without properly functioning cell cycle regulators, there are either too few or too many cells present which can cause different effects in the organism, varying in levels of harmlessness. 8. Name one harmless result of too little cell division. One harmless result is hair loss or baldness. 9. Name one harmless result of too much cell division. One harmless result of too much cell division is warts. Click on the purple section labeled “Cell Cycle Phases” as well as the words “Mitosis” and “Interphase” to read an overview of the cell cycle. You can also click on the various phases. 10. Cells go through periods of growth and division. Cell division occurs during _________Mitosis___________. The rest of the cell cycle is called interphase, during which (use the blank below to complete the sentence) the cell grows and replicates its DNA to prepare for mitosis. 11. Fill in the details about what happens during the three phases of interphase labeled in the diagram. G1: The cell comes out of mitosis and grows in size as it prepares to replicate its DNA. It passes a checkpoint that ensures the cell is healthy enough to undergo DNA replication in the following phase. S: In this phase, the DNA is replicated and is constantly checked for any errors or mutations in replication. G2: The cell matures as it grows and prepares itself for the following stage of mitosis. As the final stage in Interphase, the G2 checkpoint acts as the final inspection of DNA as the cell is preparing to duplicate. 12. In general, what is the purpose of a checkpoint in the cell cycle? A checkpoint in the cell cycle acts as a point that regulates progression from one stage of the cycle to the next without any errors in the cell or in its DNA. 13. What is the G0 phase of the cell cycle? a) Which factors determine whether a cell enters G0? Cells can enter G0 if there is a lack of resources preventing them from replicating, or if a cell is sent a signal that tells the cell to differentiate and stay in G0, putting the cell out of the cell cycle and in a resting type state. Cells typically leave the cell cycle and enter G0 in G1 after failing that checkpoint. b) Can cells leave G0? Typically cells will not leave G0 as they are fully differentiated, however in some cases, specifically in tissues such as the liver, injury can prompt them to leave G0 to help. Click on “Cell Cycle Regulators and Cancer” in the center purple circle. Read the “Regulators Overview” and then read through the “Cancer Overview” and watch the videos. 14. What are cell cycle regulators? These are proteins that either stimulate or inhibit the cells progression, giving them control over the cell cycle. They are split into proto-oncogenes and tumor suppressor genes. a) Stimulating proteins are encoded by _______________________proto-oncogenes_______________. Examples include: _____________CDK’s and CDK-cyclins______________________________________ b) Inhibitory proteins are encoded by ___________tumor suppressor genes_________________________. Examples include: ___p53, Rb, and MAD proteins_________________________________________ 15. Cancer is the result of an improperly regulated cell cycle. Describe two reasons why cells can form tumors. Tumors can form if there is rampant uncontrolled cell division or if there is too little programmed cell death in the cell cycle. Either of the two options create an overabundance of cells, causing a tumor. 16. 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 then there is issues with cells going through the final stage of differentiation. Causing a tumor to form and eventually colon cancer. 17. Normally, proto-oncogenes stimulate the cell cycle. What are oncogenes and how do they affect the cell cycle? Oncogenes are mutated versions of proto-oncogenes that cause an acceleration in the cell cycle and its stimulation. a) To cause cancer, proto-oncogenes require _____one____ allele(s) to be mutated and therefore are considered ________dominant_________ . The mutation results in a ___gain____ of function. 18. Normally, tumor suppressor genes inhibit the cell cycle. How do mutated tumor suppressor genes affect the cell cycle? Mutated tumor suppressor genes affect the cell cycle by inhibiting the cell cycle, basically slowing the cell cycle and its process. a) To cause cancer, tumor suppressor genes require _____two_____ allele(s) to be mutated and therefore are considered _______recessive________ . The mutation results in a ____loss____ of function. 19. Watch the video clip. a) Using the gas pedal analogy, explain the impact on the cell cycle of a proto-oncogene versus an oncogene. The proto-oncogene is seen as stimulating the gene or pressing the accelerator when needed, however an oncogene is seen as overstimulation, painting a picture of the accelerator being indefinitely pressed down, driving the car to its top speeds. b) Using the brake pedal analogy, explain the impact on the cell cycle of one mutated tumor suppressor gene allele versus two mutated tumor suppressor alleles. If there is only one mutated tumor allele, the effect is the same as if there are no mutated genes, pressing the brakes on the car only when prompted. However two mutated tumor suppressor alleles presents a different outcome as it appears as if the brakes are indefinitely pushed downwards, preventing any future cell cycle progression.