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Lecture 21 - Chapter 20 - Cancer - April 2.docx

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BIOL 2021
Patricia Lakin- Thomas

April 2, 2013 Chapter 20: Cancer Elisa’s Notes  Cellular and molecular level: o Characteristics of cancer cells:  2 heritable properties  1. Reproduce without normal restraints on growth or division  2. Invade and colonize new territory 2 Stages of Tumors: 1. Benign= not invasive, not cancerous (primary tumor) a. Neoplasm= growth and division without normal control 2. Malignant= invasive= cancer a. Capable of forming metastases= secondary tumors i. Found at other sites in the body Cancer as a Microevolutionary Process  For evolution to occur: o Population of organisms with heritable variation o Natural selection for individuals that have an advantage (leaving more progeny in this case)  Cancer cells acquire and pass on heritable changes to progeny cells Evidence for Heritable Changes causing cancer 1. Same mutations or chromosome rearrangements found in all cells of a tumor a. All cancerous cells in a tumor are clonal descendants of one primary tumor cell b. Figure 20-5 1. Carcinogens= anything that causes cancer a. Mutagen= anything that causes mutations in DNA b. Carcinogens are usually mutagens c. Chemicals, radiations, x-rays, UV light 1. Inherited defect in DNA repair a. Increased risk of cancer b. Ex. Xeroderma pigmentosum i. Defect in DNA repair of UV damage ii. Increase in skin cancer in these patients Evidence for accumulation of many mutations  Figure 20-7 1. Cancer incidence increases with age 2. Cancer cells accumulate mutagenic changes 3. Cancers develop gradually in tumor progression stages a. Figure 20-9, 20-11 Role of Evolution  Mutation rate o Carcinogens increase mutation rate  Number of reproducing population o Proliferate advantage o Increase of number of cells that are in a population  Rate of reproduction o Proliferative advantage increases rate of reproduction  Selective advantage of new mutants Competitive Advantages  Genetic instability o Changes in DNA maintenance genes  DNA repair, chromosome replication  Increased rate of proliferation or decreased apoptosis o Figure 20.14 o Changes in cell cycle control genes or apoptosis genes  Avoid DNA damage checkpoint – mutations inactivate checkpoints, unrepaired DNA Damage  causes more mutations o Note most cells will die, but those that survive will be much more likely to metastasize  Invading and surviving in a foreign environment – metastasis (Figure
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