What is the length in base pairs of the cytoplas mic dynein vs. kinesin double-helical DNA present in this fiber? one helical turn of the solenoid per 30 he fib ctions of the mitotic Cak(the MPF cause a2.后期A与后期 halfway through M phase. Describe the gest possible mechanisms by 七、综合问答题(任选一题,20分) 3. A protein that inhibits certain proteolytic1.细胞内蛋白质有那些分选途径?各自的机 enzymes( pro teases) is normally secreted理如 nto the bloodstream by liver cells. This inhibitor protein, antitrypsin,, is absent from2.比较裂殖酵母、芽殖酵母和哺乳动物细胞 the bloodstream of patients who carry a周期调控的异同。 mutation that results in a single amino acid hange in the protein. Antitrypsin deficiency八、附加题(每题5分,共15分) lung tissue, because of the uncontrolled 1. State the conclusion that can be drawn from activ ity of proteases. Surprisingly, when the the following finding mutant antitrypsin is synthesized in the Extracts from nondividing frog eggs in laboratory, it is as active as the normal the G2 ph Ititrypsin at inhib iting proteases. Why then were found to contain structures that does the mutation cause the disease? Think could induce the polymerization of more than one possibility and suggest f tubulin into microtubule which you could disting When examined by immunostaining. these structures were shown to contain pericentrin(中心粒旁侧蛋白) 六、比较题(每题5分,共10分) 1. Compare and contrast the 2. The signal recognition particle(SKP))5 chromatin. What is the length in base pairs of the double-helical DNA present in this fiber? Assume, for simplicity, that there is one helical turn of the solenoid per 30 nm along the fiber. 2. One of the functions of the mitotic Cdk (the MPF protein kinase) is to cause a precipitous drop in cyclin concentration halfway through M phase. Describe the consequences of this sudden decrease and suggest possible mechanisms by which it might occur. 3. A protein that inhibits certain proteolytic enzymes (proteases) is normally secreted into the bloodstream by liver cells. This inhibitor protein, antitrypsin, is absent from the bloodstream of patients who carry a mutation that results in a single amino acid change in the protein. Antitrypsin deficiency lung tissue, because of the uncontrolled activity of proteases. Surprisingly, when the mutant antitrypsin is synthesized in the laboratory, it is as active as the normal antitrypsin at inhibiting proteases. Why then does the mutation cause the disease? Think of more than one possibility and suggest ways in which you could distinguish between them. 六、比较题（每题 5 分，共 10 分） 1. Co m p ar e a nd co nt r as t th e following : cytoplas mi c dynein vs. kinesin 2. 后期 A 与后期 B 七、综合问答题(任选一题，20 分) 1. 细胞内蛋白质有那些分选途径？各自的机 理如何？ 2. 比较裂殖酵母、芽殖酵母和哺乳动物细胞 周期调控的异同。 八、附加题（每题 5 分，共 15 分） 1. State the conclusion that can be drawn from the following finding: Extracts from nondividing frog eggs in the G2 phase of the cell cycle were found to contain structures that could induce the polymerization of tubulin into microtubules in vitro. When examined by immunostaining, these structures were shown to contain pericentrin（中心粒旁侧蛋白）. 2. The signal recognition particle (SKP))