Critical Thinking Questions

31. Briefly describe the events that occur in each phase of interphase.

32. Chemotherapy drugs such as vincristine (derived from Madagascar periwinkle plants) and colchicine (derived from autumn crocus plants) disrupt mitosis by binding to tubulin (the subunit of microtubules) and interfering with microtubule assembly and disassembly. Exactly what mitotic structure is targeted by these drugs and what effect would that have on cell division?

33. Describe the similarities and differences between the cytokinesis mechanisms found in animal cells versus those in plant cells.

34. List some reasons why a cell that has just completed cytokinesis might enter the G₀ phase instead of the G₁ phase.

35. What cell-cycle events will be affected in a cell that produces mutated (non-functional) cohesin protein?

36. Describe the general conditions that must be met at each of the three main cell-cycle checkpoints.

37. Compare and contrast the roles of the positive cell-cycle regulators negative regulators.

38. What steps are necessary for Cdk to become fully active?

39. Rb is a negative regulator that blocks the cell cycle at the G₁ checkpoint until the cell achieves a requisite size. What molecular mechanism does Rb employ to halt the cell cycle?

40. Outline the steps that lead to a cell becoming cancerous.

41. Explain the difference between a proto-oncogene and a tumor-suppressor gene.

42. List the regulatory mechanisms that might be lost in a cell producing faulty p53.

43. p53 can trigger apoptosis if certain cell-cycle events fail. How does this regulatory outcome benefit a multicellular organism?

44.Name the common components of eukaryotic cell division and binary fission.

45.Describe how the duplicated bacterial chromosomes are distributed into new daughter cells without the direction of the mitotic spindle.