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Unformatted text preview: Genetics and Cellular Biology (Biol 204) Name _______________________________ EXAM FOUR April 28, 2007 Each question is worth 2 points. Circle the letter that indicates the best answer. a) b) c) d) H&J 13 H463. A mutant whose phenotype is to arrest the cell cycle at a specific and reproducible point is known as a(n) _________mutant. a) qtl b) cdc c) gef d) gpcr H464. The cell cycle is regulated by the presence and absence of cyclins, which activate ______ cdk _________ molecules that phosphorylate target proteins. H465. Which of these is NOT a way to regulate Cdk activity? a) Hydrolyze a GTP that is attached to Cdk. b) Phosphorylate Cdks. c) Inhibitor molecules such as p21 d) Subcellular localization of Cdk out of the nucleus. H466. The normal role of the RB protein is to maintain cycling cells at this point, also called start , in the cell cycle until the cell has attained the proper size: a) Prophase. b) Metaphase. c) G 1 restriction point. d) G 2 /M transition. H466. The G 1 restriction point is enforced by _____ Rb _______, which sequesters the E2F transcription factor. H468. Which of these is the key player in the mammalian DNA damage checkpoint (all are involved but which is key)? a) p21 b) p53 c) Bcl2 d) RB H468. Which of these checkpoints act at the G1/S transition? a) DNA damage checkpoint. b) Centrosome duplication checkpoint. c) Spindle assembly checkpoint. d) APC checkpoint. H470. An additional property of p21 is to combine with GADD45 to slow down DNA synthesis. It does so by affecting this property of DNA polymerase: a) kinase activity. b) processivity. c) transduction. d) contact inhibition. H472. Cells with the loss of p21 typically exhibit: a) loss of contact inhibition. 1 b) chimeric genes. c) loss of caspases. d) polyploidy. H473. Which of these is NOT involved in the spindle checkpoint? a) p53 b) Mad2 c) Cdc20 d) APC 3. Which of these proteins promotes apoptosis (HJ p 471-2)? a) Bax b) Bcl2 c) Ras d) Rb H472. Apoptosis can be induced by an increase in homodimers of Bax proteins. Which protein normally forms heterodimers with Bax in order to prevent Bax from forming homodimers? a) Ras b) RB c) Mad2 d) Bcl2 H473. Explain why a mutation in p21 causes polyploidy. (Use the terms DNA damage, p53, G 1 /S checkpoint, S phase, and G 2 /M checkpoint. Try to keep the answer to 2 or 3 short sentences.) DNA DAMAGE induces the production of p53, which leads to the arrest of the cell cycle at either the G 1 /S or the G 2 /M checkpoint. If p21 is mutated, then the cell cycle will not be arrested at the G 1 /S checkpoint and the cell will progress through S phase but will stop at the G 2 /M checkpoint. This means that the cell will double its chromosomes but will not undergo mitosis and thus will be polyploidy....
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