la A patient with stomach cancer has the tumor removed, and you isolate DNA from
ID: 93128 • Letter: L
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la A patient with stomach cancer has the tumor removed, and you isolate DNA from the tumor. You use that genomic DNA to transform normal mouse cells growing in culture to tumorigenic mouse cells (that can cause tumors when transplanted into immune-deficient mice). You then isolate DNA from these transplanted tumors and use that again to transform normal mouse cells to tumorigenic cells. The gene that led to the tumorigenic property of these mouse cells is likely to be: A. a wild type human proto-oncogene B. a mutated human proto-oncogene C. a wild type mouse proto-oncogene D. a mutated mouse proto-oncogene E. a mutant human tumor suppressor gene F a mutant mouse tumor suppressor gene 1.b. Briefly justify your answer. 1.c Is this likely to be the only mutant gene that led to the original stomach tumor? Yes or No? Why or why not? (in one sentence)Explanation / Answer
1a) mutated human proto-oncogene.
1b) -> not tumor suppressor gene because it would be a loss of function defect i.e. the gene has a function of stopping tumor which it apparently has lost. If i try and transplant it elsewhere (normal cells) the endogenous functional copy of this gene would play its normal role and not allow the tumor to develope. On the other hand proto-oncogene has a vital normal function which when expressed in an un-regulated fashion (gain-of-function) result in a tumor. In this case, the normal endogenous copy would not help.
-> not wild type because it would perform a normal function while the mutated on will be unregulated/uncontrolled.
-> not mouse because the DNA initially isolated was from a human tumor (patient's stomach cancer).
1c) No. Because once a mass of cells becaome cancerous they divide uncontrollably with one or more of the cell cycle check-points being no-functional; opening huge opportunities for new mutations to occur.
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