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The Cell CycleTEACHER NOTESCell Cycle Lesson PlanSubject Covered: Develop models of the cell cycle, explain normal division and uncontrolled cell divisionGrades Appropriate: 9-12Lesson Duration: 2-50 minute periods Lesson Plan Activity SnapshotDay 1 Formative Assessment, Engage Activity, Part A with background InformationDay 2 Part B –Tallying stages of the cell cycle using microscope and prepared onion root tip slides or cards containing enlarged photographs of onion root tips. Part C- Uncontrolled Cell Cycle (Mitosis Gone Wrong)ACOS ObjectiveACOS Biology 4 Develop and use models to explain the role of the cell cycle during growth and maintenance in multicellular organisms (e. g., normal growth and/or uncontrolled growth resulting in tumors).ACOS Appendix A:RST 1, 3WHST 2Science and Engineering Practice Crosscutting Concepts Essential Questions How much time is spent in each phase of the cell cycle and why is the amount of time relevant to the events of the phase? What happens if the cell cycle is not regulated?Students willDevelop a model of the Cell CycleIdentify stages of the cell cycleDetermine percentage of time cells spend in each phase of the cell cyclePredict changes in percentages of time spent in each phase of the cell cycle when uncontrolled cell division occursBackground InformationThe Cell CycleThe cell cycle includes interphase and mitosis. The function of interphase is growth and duplication of organelles and DNA. The function of mitosis is the accurate division of the nuclear material (i.e. chromosomes). Interphase can be further divided into G1, S, and G2 phases. Mitosis consists of four phases: prophase, metaphase, anaphase, and telophase. Cytokinesis, the division of the original cells cytoplasm, begins prior to the end of mitosis and is completed shortly after telophase.InterphaseThe cell increases in size, carries on metabolism, and the chromosomes duplicate. These events are defined as G1, S and G2. During the First Gap Phase, G1, cells increase in size for replication. The G1 phase check point allows the cell to die, rest, or move on to synthesis, which is determined by the state of the DNA and resources. If DNA is damaged or there are insufficient resources, the cell will not move to the S phase.During the Synthesis Phase, S, DNA is replicated and the cell will have two complete sets of DNA. The S phase checkpoint verifies that the DNA does not contain errors.During the Second Gap Phase, G2, the cell continues to grow and prepare for division. The G2 phase checkpoint verifies that the DNA is not damaged, chromosome sets are complete, and enough cell components are available to support to the cell.ProphaseWhen chromosomes enter prophase of mitosis, they are in the replicated state. In other words, they consist of two identical sister chromatids. Each sister chromatid is one complete DNA molecule. The sister chromatids are connected at the constriction which is called the centromere. During this phase, the nuclear envelope disintegrates.MetaphaseThe replicated chromosomes line up in the middle of the cell. The centrosome is located in the cytoplasm attached to the outside of the nucleus. It consists of two centrioles which are oriented at right angles to each other and embedded in a mass of amorphous material. The centrosome is duplicated during S phase of the cell cycle. Just before mitosis, the two centrosomes move apart until they are on opposite sides of the nucleus. As mitosis proceeds, microtubules grow out from each centrosome with their plus ends growing toward the metaphase plate. These clusters of microtubules are called spindle fibers. The spindle fibers attach to the centromere of each dyad.AnaphaseThe centromere splits as a result of a protein complex assembled at each centromere which serves as the attachment point for the spindle microtubules. This protein complex is called a kinetochore. Each sister chromatid is moved to the opposite side of the cell by the contraction of the attached spindle fiber. At the end of this stage the chromosomes are un-replicated chromosomes.TelophaseThe spindle apparatus dissolves and the nuclear envelope reforms. The cytoplasm divides and the end of mitosis is marked by a complete division of the daughter cells (by the process of cytokinesis).Common Student MisconceptionsWhen modeling the cell cycle, remind students that the Law of Segregation allows the sister chromatids to separate and migrate as independent chromosomes. Students frequently keep pipe cleaners of the same color together.ENGAGE Formative Assessment: Card SortStudent groups will receive a baggie containing 5 cards with each card representing one stage of the cell cycle. Students will place the cards in order. After completing Part A and Part B, allow students to rearrange the order of the cards if desired.KWLStudents will fold a piece of paper in a burrito fold with three sections of equal size. The far left should be titled “what I know about the cell cycle.” The middle should be titled “what I would like to know find out about the cell cycle.” The far right should be titled “what I have learned about the cell cycle.” Three minutes should be provided for students to complete the left and middle sections. The last section will be completed on day two.Pre-labMaterials2 pipe cleaners of one color and 2 of another colorDrawing paperBuilding chromosomes with pipe cleaners and simulating the cell cycle, Part A. Student sketches of each phase and pipe cleaner positioning should be similar to the clip art diagram below. Formative Assessment: I Think / We Think ActivityEach student will fold a piece of notebook paper, hot dog fold, and on the top left use the heading “I think” and on the top right use the heading “We think”. Ask each student to list the phases of the cell Cycle and predict which phase is the longest and which is the shortest under the “I think” heading.Allow students in groups of four to share their list and predictions. After three minutes of group discussion, each student will be given time to fill in the “We think” side of the paper based on information shared.EXPLOREMaterialsPencil Microscopes Mitosis Cards (optional) Onion Root Tip Slides Calculator Colored PencilsEXPLAINInteractive web site with student handouts is located at from Student HandoutPart A.How are chromosomes different in prophase and metaphase than in anaphase and telophase?Chromosomes exist as duplicated dyads in prophase and metaphase. In Anaphase and telophase the sister chromatids split and are now independent monads.2.What is the difference between chromatids and chromosomes?Chromatids only exist as part of the duplicated chromosomes.3.Why does mitosis occur?For growth and repair.4.What is the significance of the process of mitosis? The process is significant in ensuring the correct separation of genetic material.5.What is the final stage of mitotic division?Telophase Part B.DATAPlace tally marks in the appropriate columns for each cell counted.INTERPHASEPROPHASEMETAPHASEANAPHASETELOPHASETotal ________Total ________Total ________Total ________Total ________75-90_% 8 – 15 %2-5% 1-3 % 3- 7%InterphaseProphaseMetaphaseAnaphaseTelophaseNumber of hours in each phase:6. Predict which phase of Mitosis is the longest? __any phase of mitosis____ Shortest?_any phase of mitosis7. Refer to your data to answer the following questions:What is the longest phase of the cell cycle? InterphaseWhat is the longest phase of mitosis? ProphaseWhat is the shortest phase of the cell cycle? AnaphaseWhat is the shortest phase of mitosis? Anaphase8.Describe the cell plate that was present during telophase. How would telophase differ in an animal cell?The cell plate was rigid and linear. In the animal cell there would be a pinching in of the cytoplasm (cleavage furrow).9.If the pie chart below represents 24 hours in the life of an onion cell, color in the amount of time spent in each phase based on your calculations. KEY: Interphase Prophase Metaphase Anaphase TelophaseEVALUATE Formative Assessment: Card Sort with 5 cards in baggies. Each card represents a stage of the cell cycleKWL ActivityI Think / We Think Activity after pipe cleaner modeling Part A.Observe pipe cleaner positioning and sketches during the Pre-Lab activity Part A.Summative Assessment Student Data SheetFormal Lab Write-upTROUBLESHOOTING & SAFETYMitosis cards may be used to substitute prepared slides of the onion root tips if microscope focusing is an issue.It is very important to make certain that the students are focused on the root tip of the slide.Do not use electrical cords if frayed, nicked and/or missing one of the 3 prongs. ELABORATEPart C. Background InformationWhy do cells become mutated and divide uncontrollably? There are many reasons. Cancer is a genetic disorder but few types are inherited. The majority of cancers are caused by carcinogens. Carcinogens are DNA damaging agents which cause mutations that lead to cancer formation. Ultraviolet light and ionizing radiation are two types of physical carcinogens. Tobacco, asbestos and arsenic are chemical carcinogens. Infections from certain viruses, bacteria and parasites are known as biological carcinogens. There are check points; also known as stopping points, in the cell cycle to make sure everything is correct before going on to the next phase. The check points are located at the end of G1, end of S, end of G2, and at the end of Metaphase. One or more cancerous cell check points are non-functional. Additional information is available on check points and cancer formation at cancer cells are undetected and untreated a tumor could eventually form. There are basically two types of tumors, benign and malignant. Benign tumors contain cells that do not travel to other tissues or parts of the body. Malignant tumors do have cells that can break off and migrate to other parts of the body and invade healthy tissues causing harm. The term metastasis is used to describe cells that have spread from their point of origin.Analysis Part C.Predictions (Interphase should decrease and the other phases should increase when compared to data collected in Part B.)________%________%________%_______%________%InterphaseProphaseMetaphaseAnaphaseTelophase Normal cells in the body spend most of their time in which phase of the cell cycle? Why? Interphase is the phase prior to and after mitosis. This is the time for cell growth. Would you expect the percentages of cells in each phase of the cell cycle to change if uncontrolled cell division occurred? Explain your answer.Yes, the cell will be dividing at a rapid rate, decreasing the time in interphase. The percentage of time for interphase would decrease and an increased percentage of time should be seen in each of the phases of mitosis (prophase, metaphase, anaphase, and interphase). 12. Cancer is when _______cell division_______ is uncontrolled. How are cancer cells different from normal cells?Cancer cells spend less time in interphaseCancer cells have uncontrolled mitosis- they do not stop dividing after a certain point.Cancer cells grow faster than normal cells.Cancer cells lack one or more check points, stopping points, which make sure everything is correct before going on to the next phase. List and give examples of three different types of carcinogens. Chemical carcinogens- Tobacco, asbestos and arsenicBiological carcinogens- Infection from certain viruses, bacteria and parasitesPhysical carcinogens-Ultraviolet light, ionizing radiation What is the purpose of check points in the cell cycle?The check points, if functioning properly, verify the cell is ready to move on to the next phase of the cell cycle. They prevent cells from dividing that contain pare the normal tissue with the cancerous tissue on the handout. In the chart below tally the number of cells in each phase of mitosis for the normal tissue. Answers will varyPROPHASEMETAPHASEANAPHASETELOPHASE In the chart below tally the number of cells in each phase of mitosis for the cancerous tissue.Answers will vary but should contain a greater number than in #16 the normal tissue tally .PROPHASEMETAPHASEANAPHASETELOPHASE18. Explain differences seen in the phases of the cell cycle when comparing the normal tissue with cancerous tissue. The cancerous tissue should contain a greater number of cell in the phases of mitosis and few cells in Interphase when compared with normal tissue due to the uncontrolled rate of division in cancer cells.19. Consider the following statement: The majority of cancers are genetic in nature, with only about 5% resulting from inheritance. Explain this statement.Only 5% is believed to be directly inherited from parents. A life time of exposure to carcinogens can cause mutation to occur in the DNA of cells. Cancer is a genetic disorder because the DNA is altered.Additional information concerning cell division in cancerous tissue can be found at the following website. student handouts to complete while viewing the hhmi biointeractive presentation.Click and Learn: The Eukaryotic Cell Cycle and Cancer. Extension View whitefish slides making a tally and determining percentages of time spend in each phase of the cell cycle. Compare whitefish results with onion root tips and note similarities and differences between the animal and plant cell cycle slides. Research and answer the question: How does cancer differ in plants? Source(s): ... A Tree tumor of unknown origin . Focus on Cancer DVD, Russel Hill Cancer Foundation, Clearview Cancer InstituteDNA Interactive DVD, ................
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