Chapter 9 for Courseweb

Chapter 9 for Courseweb - 9 Chromosomes, the Cell Cycle,...

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9 Chromosomes, the Cell Cycle, and Cell Division
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9 Chromosomes, the Cell Cycle, and Cell Division Why must cells divide? How do prokaryotes and eukaryotes divide? What is the cell cycle? How is it controlled? What happens during mitosis and meiosis? Why is Meiosis Important in Sexual Reproduction? How Do Cells Die?
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Why do cells divide?
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What are the consequences of cell division?
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9.1 How Do Prokaryotic and Eukaryotic Cells Divide? Four events must occur for cell division: Reproductive Signal : to initiate cell division Replication : of DNA Segregation : distribution of the DNA into the two new cells Cytokinesis : separation of the two new cells
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9.1 How Do Prokaryotic Cells Divide? Prokaryotes divide by binary fission Reproductive signals: nutrient availability and environmental conditions Prokaryotes have one chromosome - a single circular molecule of DNA ori —where replication starts Separation of chromosome and cytokinesis
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Figure 9.2 Prokaryotic Cell Division
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9.1 How do Eukaryotic Cells Divide? Eukaryotes: Complex intracellular organization Multicellular forms that originate from a single cell formed by fusion of gametes from both parents Have more than one chromosome Signal for cell division based on the needs of the whole organism
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9.1 How Do Eukaryotic Cells Divide? Nucleus must be divided : Mitosis and Meiosis Cytokinesis separates the cytoplasm Mitosis results in two identical cells Meiosis occurs in cells that produce gametes
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9.2 How Is Eukaryotic Cell Division Controlled? The cell cycle : Time between two successive cell divisions Cell Cycle: 2 phases Interphase: Time between nuclear 2 divsions, 3 subphases Mitosis: Division of nuclei
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Figure 9.3 The Eukaryotic Cell Cycle G0 G1 S G2 M
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9.2 How Is Eukaryotic Cell Division Controlled?
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9.2 How Is Eukaryotic Cell Division Controlled? Transitions depend on activation of the protein cyclin-dependent kinase (Cdk). Cdk is activated by binding to cyclin The cyclin-Cdk complex phosphorylates target proteins that allow cell cycle to progress past restriction point
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Figure 9.5 Cyclin Binding Activates Cdk Several kinds of Cdks and Cyclins are present in the cell
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Figure 9.6 Cyclin-Dependent Kinases and Cyclins Trigger Transitions in the Cell Cycle
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9.2 How Is Eukaryotic Cell Division Controlled? Cancer is a result of inappropriate cell division—the cyclin-Cdk controls are disrupted. Tumor suppressor proteins like p53, p21, Rb maybe defective. Over half of human cancer cells have defective p53.
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9.2 How Is Eukaryotic Cell Division Controlled? Not all cells go through the cell cycle regularly Some cells no longer divide, or divide infrequently. These cells can be stimulated to divide by Growth factors Platelet-derived growth factor, interleukins, erythropoietin
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For cancer chemotherapy, a suitable agent could be one that blocks which stage of the cell cycle? A. G1
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Chapter 9 for Courseweb - 9 Chromosomes, the Cell Cycle,...

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