Chapter 12

A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in a. prophase b. anaphase c. meaphase d. G1 e. G2

d

For anaphase to begin, which of the following must occur? a. Spindle microtubules must begin to depolymerize. b. Cohesin must attach the sister chromatids to each other. c.Kinetochores must attach to the metaphase plate. d. Cohesin must be cleaved enzymatically. e. Chromatids must lose their kinetochores. 0

d

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely. a. plant cell in metaphase b. an animal cell in the s phase of the cell cycle c. a bacterial cell dividing d. a plant cell in the process of cytokinesis e. an animal cell in the process of cytokinesis

d

The centromere is a region in which a. new spindle microtubules form at either end. b. metaphase chromosomes become aligned at the metaphase plate. c. the nucleus is located prior to mitosis. D. chromatids remain attached to one another until anaphase. E. chromosomes are grouped during telophase.

D

A mutation results in a cell that no longer produces a normal protein kinase for the M phase checkpoint. Which of the following would likely be the immediate result of this mutation? a. The cell would undergo normal mitosis, but fail to enter the next G1 phase. b. The cell would never leave metaphase. c. The cell would never enter metaphase. d. The cell would prematurely enter anaphase. e. The cell would never enter prophase.

a

Where do the microtubules of the spindle originate during mitosis in both plant and animal cells? a. centrosome b. kinetochore c. centriole d.chromatid e. centromere

a

Why do chromosomes coil during mitosis? a. to allow the chromosomes to move without becoming entangled and breaking b. to allow the chromosomes to fit within the nuclear envelope c. to increase their potential energy d. to provide for the structure of the centromere e. to allow the sister chromatids to remain attached

a

The cylinder component of MPF is destroyed toward the end of which phase a. G2 b. G1 c. G0 d. S E. M

E.

Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic nucleus. It might consist of which of the following? a. two chromatids attached together at a centromere b. two long strands of DNA plus proteins c. one-twlth of the genes of the organism d. two chromosomes, each with six chromatids e. a single circular piece of DNA

b

The MPF protein complex turns itself off by a. activating an enzyme that stimulates cyclin b. activating a process that destroys cycling components c. binding to chromatin d. activating the anaphase-promoting complex e. exiting the cell

b

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells? a. cyclin-dependent kinases b. Golgi- derived vesicles c. centrioles and centromers d. kinetochores e. actin and myosin.

b

Besides the ability of some cancer cells to over proliferate, what else could logically result in a tumor? a. changes in the order of cell cycle stages b. lack of appropriate cell death c. metastasis d. inability of chromosomes to met at the metaphase plate e. inability to form spindles.

b.

At which phase are centrioles beginning to move apart in animal cells? a. anaphase b. telophase c. prophase d. metaphase e. prometaphase

c

Movement of the chromosomes during anaphase would be most affected by a drug that a. reduces cyclin concentrations. b. increases cyclin concentrations. c. prevents shortening of microtubules. d. prevents elongation of microtubules. e. prevents attachment of the microtubules to the kinetochore.

c

One difference between cancer cells and normal cells is that cancer cells a. are unable to synthesize DNA b. are arrested at the S phase of the cell cycle c. continue to divide even when they are tightly packed together. d. are always in the M phase of the cell cycle e. cannot function properly because they are affected by density-dependly inhibition.

c

Which of the following most accurately describes a cyclin? a. it is activated to phosphorylate by complexing with a CDK. b. it activates a Cdk when its concentration is decreased c. it activates a Cdk molecule when it is in sufficient concentration d. it is present in similar concentrations throughout he cell cycle. e. It decreases in concentration when MPF activity increases.

c.

Which of the following best describes how chromosomes move toward the poles of the spine during mitosis? a. Nonkinetochore spindle fibers serve to push chromosomes in the direction of the poles. b. The chromosomes are "reeled in" by the contraction of spindle microtubules, motor proteins of the kinetochores move the chromosomes along the spindle microtubules, and nonkinetochore spindle fibers serve to push chromosomes in the direction of the poles. c. Motor proteins of the kinetochores move the chromosomes along the spindle microtubules. d. The chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules. e. The chromosomes are "reeled in" by the contraction of spindle microtubules.

d

Which of the the following does not occur during mitosis? a. cell cycles lacking an s phase b. separation of sister chromatids c. spindle formation d. replication of the DNA e. condensation of the chromosomes

d

If there are 20 chromatids in a cell, how many centromeres are there? a. 40 b. 80 c. 30 d. 20 e.10

e

Which of the following triggers the cells passage past the G2 checkpoint into mitosis a. CDK b. PDGF c. Cyclin d. Protein kinase e. MPF

e