Chapter 18
49.The size of a human organ often depends on: A. the death of cells during its development. B. the proliferation of cells during its development. C. the size of its cells. D. All of the above
D. All of the above
18.The cell-cycle control system uses which of the following methods to halt the cycle? A. It uses Cdk inhibitors. B. It inhibits the phosphatases required to activate a Cdk. C. It inhibits the activation of APC to prevent the degradation of M-cyclin. D. All the above
D. All the above
19.During G1, cells: A. grow. B. destroy their cyclins. C. repair DNA damage. D. All the above. E. A and C only.
D. All the above.
2.Which of the following processes occur only in S phase of the cell cycle? A. Organelle replication B. Cell growth C. Chromosome segregation D. DNA replication
D. DNA replication
14.The inactivation of M-Cdk leads to which of the following? A. Onset of mitosis B. Onset of G2 phase C. Exit from S phase D. Exit from mitosis
D. Exit from mitosis
31.The five stages of mitosis occur in which order? A. Anaphase, prometaphase, metaphase, telophase, prophase B. Prophase, metaphase, prometaphase, telophase, anaphase C. Telophase, anaphase, prophase, prometaphase, metaphase D. Prophase, prometaphase, metaphase, anaphase, telophase E. Anaphase, telophase, prometaphase, metaphase, prophase
D. Prophase, prometaphase, metaphase, anaphase, telophase
32.In the cell cycle, duplication of the centrosome begins in: A. G1 phase. B. M phase. C. prophase. D. S phase. E. G2 phase.
D. S phase.
27.The activation of M-Cdk begins abruptly mainly because: A. M cyclin increases abruptly. B. M cyclin is rapidly phosphorylated and thereby activated. C. the mitotic Cdk increases abruptly. D. each M-Cdk complex can activate more M-Cdk. E. All of the above
D. each M-Cdk complex can activate more M-Cdk.
6.The basic organization and machinery of the cell cycle is: A. essentially the same in all living things. B. fundamentally different in plant and animal cells. C. essentially the same in all single-celled organisms. D. essentially the same in all eukaryotes.
D. essentially the same in all eukaryotes.
36.Microtubules capture chromosomes by binding to: A. centromere regions of the sister chromatids. B. cohesins on the sister chromatids. C. condensins on the condensed chromosomes. D. kinetochores on the sister chromatids.
D. kinetochores on the sister chromatids.
16.The cell-cycle control system uses Cdk inhibitory proteins: A. to stop one phase of the cycle and trigger another. B. to degrade Cdks. C. to degrade cyclins. D. to arrest the cell cycle at specific checkpoints.
D. to arrest the cell cycle at specific checkpoints.
20.If the cell is deprived of mitogens for a prolonged period of time, it will enter a non-proliferating state in which it may remain for: A. days. B. weeks. C. months. D. the remaining lifetime of the organism. E. All the above
E. All the above
46.The contractile ring is made of: A. microtubules. B. actin and myosin. C. condensins. D. cohesins. E. integrins.
B. actin and myosin.
39.Chromosomes line up at the spindle equator during: A. telophase. B. metaphase. C. prophase. D. anaphase.
B. metaphase.
30.The mitotic spindle is made of: A. actin. B. microtubles. C. condensins. D. cohesins. E. All of the above
B. microtubles.
52.When a cell is acutely injured, it usually dies by: A. apoptosis. B. necrosis. C. endocytosis. D. phagocytosis.
B. necrosis.
33.In the cell cycle, the mitotic spindle begins to assemble in: A. prometaphase. B. prophase. C. metaphase. D. anaphase. E. telophase.
B. prophase.
35.The nuclear envelope breaks down at the start of prometaphase because: A. the replicated chromosomes decondense. B. proteins that form the nuclear pores and nuclear lamina become phosphorylated. C. the sister chromatids separate. D. the growing mitotic spindle breaks the envelope down.
B. proteins that form the nuclear pores and nuclear lamina become phosphorylated.
43.The reassembly of the nuclear envelope at telophase depends on: A. the phosphorylation of nuclear lamins and nuclear of pore proteins. B. the dephosphorylation of both nuclear lamins and nuclear pore proteins. C. the dephosphorylation of M cyclin. D. the phosphorylation of M cyclin.
B. the dephosphorylation of both nuclear lamins and nuclear pore proteins.
7.Different cyclin-dependent protein kinases (Cdks) trigger different stages of the cell cycle in part because: A. their concentrations increase at different stages of the cycle. B. their activities increase at different stages of the cycle. C. they are degraded at different stages of the cycle. D. All of the above
B. their activities increase at different stages of the cycle.
11.Which of the following statements is false? A. Activated M-Cdk triggers the onset of cytokinesis. B. Activated S-Cdk initiates DNA replication. C. G1-Cdks and G1/S-Cdks help drive cells through G1 into S phase.
A. Activated M-Cdk triggers the onset of cytokinesis.
25.The signal to commence DNA replication comes from: A. S-Cdk. B. ORC. C. the destruction of Cdc6. D. the destruction of M-Cdk.
A. S-Cdk.
15.For a cyclin-Cdk complex to be maximally active, it has to be phosphorylated at one site by a specific protein kinase and dephosphorylated at other sites by specific protein phosphatases. A. True B. False
A. True
22.p53 can induce the cell to kill itself if damage to its DNA is very severe. A. True B. False
A. True
29.The cytoskeleton carries out both mitosis and cytokinesis. A. True B. False
A. True
53.Apoptosis depends on a tightly regulated proteolytic cascade. A. True B. False
A. True
57.Many cells in normal animal tissues require extracellular signals from other cells to avoid apoptosis. This could be a mechanism for ensuring that cells only survive when and where they are needed. A. True B. False
A. True
59.Cell growth, unlike cell proliferation, does not depend on the cell-cycle control system. A. True B. False
A. True
61.Cancer cells fail to obey normal "social" controls on cell behavior and therefore outgrow, out-divide and out-survive their normal neighbors. A. True B. False
A. True
9.For a Cdk to be active, it must: A. bind a cyclin. B. increase in concentration at a specific time in the cycle. C. dissociate from its bound cyclin. D. translocate from the cytoplasm to the nucleus.
A. bind a cyclin.
40.The anaphase promoting complex (APC) triggers the onset of anaphase by: A. precipitating the destruction of the cohesins that holds the sister chromatids together. B. precipitating the destruction of the condensins that keep the replicated chromosomes in a condensed state. C. stimulating the spindle poles to move apart. D. All of the above
A. precipitating the destruction of the cohesins that holds the sister chromatids together.
17.The cell cycle control system initiates chromosome segregation only after: A. the duplicated chromosomes are correctly aligned on the mitotic spindle. B. DNA has been completely replicated and the chromosomes have decondensed. C. the cell stops growing. D. cytokinesis is complete.
A. the duplicated chromosomes are correctly aligned on the mitotic spindle.
54.Which of the following statements are is false? A. Some Bcl2 family members promote apoptosis, whereas others inhibit apoptosis. B. The death-promoting members of the Bcl2 family include Bcl2 itself. C. Bax and Bak are death-promoting members of the Bcl2 family that induce the release of cytochrome c from mitochondria into the cytosol. D. Some death-inhibiting members of the Bcl2 family inhibit apoptosis by blocking cytochrome c release from mitochondria.
B. The death-promoting members of the Bcl2 family include Bcl2 itself.
37.Which of the following statements is false? A. The microtubules bound to a mitotic chromosome must attach to opposite poles of the spindle for the daughter chromosomes to be segregated properly. B. The pairing of homologous chromosomes during prometaphase is called bi-orientation. C. Attachment of mitotic chromosomes to both poles of the spindle creates tension, which signals the chromosomes are ready to be separated. D. The cell cycle control system monitors the tension on the kinetochores to ensure correct chromosome attachment.
B. The pairing of homologous chromosomes during prometaphase is called bi-orientation.
58.Which of the following statements describes how mitogens operate? A. They suppress apoptosis. B. They overcome the intracellular braking mechanisms that tend to block progression through the cell cycle. C. They directly phosphorylate and activate Cdks.
B. They overcome the intracellular braking mechanisms that tend to block progression through the cell cycle.
26.If DNA is damaged or incompletely replicated in S phase, what molecule's inhibition prevents the cell from entering M phase? A. Cdc6 B. Cdc25 C. S-Cdk D. ORC
B. Cdc25
8.Which of the following statements is false? A. Cyclins vary in concentration at different stages of the cell cycle. B. Cyclins help activate Cdks by phosphorylating them. C. Cyclins are degraded at specific times in the cell cycle. D. Cyclins have no enzymatic activity on their own.
B. Cyclins help activate Cdks by phosphorylating them.
12.Different cyclins always bind to different Cdks. A. True B. False
B. False
21.If the Rb protein binds to transcription regulators, the cell will move from G1 phase to S phase. A. True B. False
B. False
4.During the cell cycle, cell growth occurs only in the gap phases, G1 and G2. A. True B. False
B. False
44.Mitosis always produces daughter cells of equal size. A. True B. False
B. False
45.The location of the nucleus determines the site of cleavage during cytokinesis. A. True B. False
B. False
51.Apoptosis is a form of programmed cell death, in which cells kill themselves by migrating to the blood stream where they are carried to the liver for destruction. A. True B. False
B. False
56.Survival factors act primarily by stimulating cell division. A. True B. False
B. False
5.Which of the following statements is false? Checkpoints of cell-cycle control system ensure that: A. the environment is favorable for the cell to initiate DNA replication. B. M phase is completed before cytokinesis begins. C. all chromosomes are attached to the mitotic spindle before the chromosomes are segregated to the two daughter cells. D. all DNA is replicated before M phase begins.
B. M phase is completed before cytokinesis begins.
1.Which two processes together constitute the M phase of the cell cycle? A. Interphase and mitosis B. Mitosis and cytokinesis C. Interphase and metaphase D. S phase and G1
B. Mitosis and cytokinesis
34.Which of the following statements is true? A. The mitotic spindle is made primarily of microtubules and actin filaments. B. New microtubules grow out in random directions from the centrosomes. C. The dynamic instability of microtubules decreases at the start of mitosis. D. The minus end of a microtubule has a net negative charge, whereas the positive end has a net positive charge.
B. New microtubules grow out in random directions from the centrosomes.
47.In dividing plant cells, a new cell wall is formed between two sets of chromosomes via a structure called a phragmoplast, which is built by vesicles largely originating from which organelle? A. The endoplasmic reticulum B. The Golgi apparatus C. The vacuole D. The chloroplasts E. Vesicles from the broken down nuclear envelope
B. The Golgi apparatus
48.Which of the following organelles fragments during mitosis? A. Mitochondria B. The Golgi apparatus C. The peroxisomes D. The lysozomes E. Chloroplasts
B. The Golgi apparatus
24.Which of the following statements is false? A. The activation of S-Cdk initiates DNA replication. B. The activation of S-Cdk helps prevent the onset of M phase. C. DNA replication occurs only in S phase. D. The activation of S-Cdk helps prevent DNA replication occurring more than once each cycle.
B. The activation of S-Cdk helps prevent the onset of M phase.
41.Which of the following processes does NOT help move the daughter chromosomes to opposite poles of the spindle in anaphase? A. Kinetochore microtubules shorten by depolymerization. B. The spindle poles move apart. C. Actin and myosin filaments in the spindle contract. D. Microtubule motor proteins hydrolyze ATP at the kinetochores.
C. Actin and myosin filaments in the spindle contract.
50.Which of the following statements is true? A. Many cells die by necrosis during normal animal development. B. Many cells die by necrosis in many normal, adult, human tissues. C. Many cells die by apoptosis in many normal, adult, human tissues.
C. Many cells die by apoptosis in many normal, adult, human tissues.
23.Which of the following is FALSE about cells that are in G0? A. They retain the ability to reassemble the cell-cycle control system. B. They can divide if the need arises but normally do so infrequently. C. Their cell-cycle control system is dismantled completely. D. They can be stimulated to proliferate if the surrounding tissue is damaged.
C. Their cell-cycle control system is dismantled completely.
60.Which of the following statements describe how growth factors stimulate animal cell enlargement? A. They stimulate microtubule polymerization. B. They stimulate an influx of extracellular water into the cytosol. C. They stimulate intracellular protein synthesis. D. They stimulate DNA replication.
C. They stimulate intracellular protein synthesis.
42.The spindle assembly checkpoint, which blocks the initiation of anaphase until all chromosomes are properly attached to the mitotic spindle, depends on: A. cohesin degradation. B. M-cyclin degradation. C. an inhibitory signal produced by inappropriately attached chromosomes. D. a stimulatory signal produced by appropriately attached chromosomes.
C. an inhibitory signal produced by inappropriately attached chromosomes.
10.The loss of its cyclin causes a Cdk to: A. become active. B. be degraded in proteasomes. C. become inactive. D. phosphorylate its target proteins.
C. become inactive.
28.The shortening and thickening of chromosomes in M phase depends on: A. microtubules. B. actin and myosin. C. condensins. D. cohesins. E. All of the above
C. condensins.
55.External signals can stimulate apoptosis by activating a set of cell-surface receptors known as: A. suicide receptors. B. caspase receptors. C. death receptors. D. Bax receptors.
C. death receptors.
3.The period betweenone M phase and the subsequent M phase is called: A. S phase. B. anaphase. C. interphase. D. G2 phase.
C. interphase.
13.At specific times in the cell cycle: A. some cyclins are phosphorylated and degraded in proteasomes. B. some Cdks are ubiquitylated and degraded in proteasomes. C. some cyclins are ubiquitylated are degraded in proteasomes. D. some Cdks are phosphorylated and degraded in proteasomes.
C. some cyclins are ubiquitylated are degraded in proteasomes.
38.Cells without centrosomes can still assemble a functional bipolar mitotic spindle, because: A. nuclear pore complexes can nucleate microtubule assembly. B. microtubules can organize themselves into a bipolar spindle. C. the chromosomes themselves can nucleate microtubule assembly. D. motor proteins can nucleate microtubule assembly.
C. the chromosomes themselves can nucleate microtubule assembly.
