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2008 Exam 1 key - Name Bio 336/391M Exam 1 Feb 13 2008 1(8...

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Name ________________________ Bio 336/391M Exam 1 Feb. 13, 2008 1. (8) The “Ames Test” was important because it solidified the notion that many carcinogens are mutagens. However, the test, itself, has important limitations when it comes to identifying human carcinogens. Give two examples where a known human carcinogen would fail to score positive in the test, and explain why. Asbestos is a chemically inert fiber that is not internalized into cells; it would not score positive as a mutagen. While the “modified” Ames test attempts to account for conversion of non-mutagenic compounds into reactive compounds by the inclusion of liver enzymes, it is very possible that some carcinogens would still be missed in the assay. Inert implanted objects that induce sarcomas when in rodents (see lecture notes) Clearly microbes/viruses associated with human cancer would not score positive 2. (8) State two important general and/or experimental observations that support the idea that carcinogenesis is a multi-step process. Correlation of pathologic intermediates in colon cancer with specific genetic alterations Age-dependency Retention of 8:21 chromosomal translocation in stem cells of “cured” AML patients Time between exposure to carcinogens and development of cancer 3. Stem cells. A. (6) For most types of cancer, what are two important reasons why it is difficult to address the question of whether tissue stem cells were the target or initiating cell in carcinogenesis? It is still difficult to even identify stem cells for most tissue types Even if you can identify them, it is very difficult to identify systems where you can track the cell lineage of cancer, particularly given the time scale of cancer development. B. (6) Regardless of whether cancer initiates in the stem cells of a given tissue, there is evidence consistent with the idea that cancers have a population of stem cell-like cells (cancer stem cells).
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