C HALLENGING P ROBLEMS 12. Cancer is thought to be caused by the accumula-tion of two or more “hits”—that is, two or more mutations that affect cell proliferation and survival in the same cell. Many of these oncogenic muta-tions are dominant: one mutant copy of the gene is sufficient to change the proliferative properties of a cell. Which of the following general types of muta-tions have the potential to create dominant onco-genes? Justify each answer. a. a mutation that increases the number of copies of a transcriptional activator of cyclin A b. a nonsense mutation located shortly after the beginning of translation in a gene that encodes a growth-factor receptor c. a mutation that increases the level of FasL d. a mutation that disrupts the active site of a cyto-plasmic tyrosine-specific protein kinase e. a translocation that joins a gene encoding an inhibitor of apoptosis to an enhancer element for gene expression in the liver 13. Many of the proteins that participate in the pro-gression pathway of the cell cycle are reversibly modified, whereas, in the apoptosis pathway, the modification events are irreversible. Rationalize these observations in relation to the nature and end
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.