12
44) Why do neurons and some other specialized cells divide infrequently?
A) They no longer have active nuclei.
B) They no longer carry receptors for signal molecules.
C) They have been shunted into G0.
D) They can no longer bind Cdk to cyclin.
E) They show a drop in MPF concentration.
45) Which of the following most accurately describes a cyclin?
A) It is present in similar concentrations throughout the cell cycle.
B) It is activated to phosphorylate by complexing with a Cdk.
C) It decreases in concentration when MPF activity increases.
D) It activates a Cdk molecule when it is in sufficient concentration.
E) It activates a Cdk when its concentration is decreased.
46) All cell cycle checkpoints are similar in which way?
A) They respond to the same cyclins.
B) They utilize the same Cdks.
C) They give the go-ahead signal to progress to the next checkpoint.
D) They each have only one cyclin/Cdk complex.
E) They activate or inactivate other proteins.
47) At the M phase checkpoint, the complex allows for what to occur?
A) Separase enzyme cleaves cohesins and allows chromatids to separate.
B) Cohesins alter separase to allow chromatids to separate.
C) Kinetochores are able to bind to spindle microtubules.
D) All microtubules are made to bind to kinetochores.
E) Daughter cells are allowed to pass into G1.
48) What explains anchorage dependence of animal cells in vitro or in vivo?
A) attachment of spindle fibers to centrioles
B) response of the plasma membrane to cell cycle controls
C) the makeup of the extracellular matrix of the substrate
D) the binding of cell-surface phospholipids to those of adjoining cells
E) the binding of cell-surface phospholipids to the substrate
49) A research team began a study of a cultured cell line. Their preliminary observations showed them
that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What
could they conclude right away?
A) The cells originated in the nervous system.
B) The cells are unable to form spindle microtubules.
C) They have altered series of cell cycle phases.
D) The cells show characteristics of tumors.
E) They were originally derived from an elderly organism.
50) For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most
desirable?
A) It is safe enough to limit all apoptosis.
B) It does not alter metabolically active cells.
C) It only attacks cells that are density dependent.
D) It interferes with cells entering G0.
E) It interferes with rapidly dividing cells.
51) You have a series of cells, all of which were derived from tumors, and you first need to find out
which ones are malignant. What could you do?
A) See which ones are not overproliferating.
B) Find out which ones have a higher rate of apoptosis.
C) Karyotype samples to look for unusual size and number of chromosomes.
D) Measure metastasis.
E) Time their cell cycles.
Art Questions
Use the following information to answer the questions below.
The lettered circle in Figure 12.1 shows a diploid nucleus with four chromosomes. There are two pairs
of homologous chromosomes, one long and the other short. One haploid set is symbolized as black and
the other haploid set is gray. The chromosomes in the unlettered circle have not yet replicated. Choose
the correct chromosomal conditions for the following stages.
Figure 12.1
52) What is the correct chromosomal condition at the prometaphase of mitosis?
A) A
B) B
C) C
D) D
E) E
53) What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?
A) A
B) B
C) C
D) D
E) E
Figure 12.2
54) If the cell whose nuclear material is shown in Figure 12.2 continues toward completion of mitosis,
which of the following events would occur next?
A) cell membrane synthesis
B) spindle fiber formation
C) nuclear envelope breakdown
D) formation of telophase nuclei
E) synthesis of chromatids
The following questions are based on Figure 12.3.
Figure 12.3
55) In the figure above, mitosis is represented by which numbered part(s) of the cycle?
A) I
B) II
C) III
D) IV
E) V
56) G1 is represented by which numbered part(s) of the cycle?
A) I or V
B) II or IV
C) III only
D) IV only
E) V only
57) Which number represents DNA synthesis?
A) I
B) II
C) III
D) IV
E) V
58) Which number represents the point in the cell cycle during which the chromosomes are replicated?
A) I
B) II
C) III
D) IV
E) V
59) At which of the numbered regions would you expect to find cells at metaphase?
A) I and IV
B) II only
C) III only
D) IV only
E) V only
60) MPF reaches its threshold concentration at the end of this stage.
A) I
B) II
C) III
D) IV
E) V
Use the data in Table 12.1 to answer the following questions.
The data were obtained from a study of the length of time spent in each phase of the cell cycle by cells
of three eukaryotic organisms designated beta, delta, and gamma.
Table 12.1: Minutes Spent in Cell Cycle Phases
61) Of the following, the best conclusion concerning the difference between the S phases for beta and
gamma is that
A) gamma contains more DNA than beta.
B) beta and gamma contain the same amount of DNA.
C) beta cells reproduce asexually.
D) gamma contains 48 times more DNA and RNA than beta.
E) beta is a plant cell and gamma is an animal cell.
62) The best conclusion concerning delta is that the cells
A) contain no DNA.
B) contain no RNA.
C) contain only one chromosome that is very short.
D) are actually in the G0 phase.
E) divide in the G1 phase.
Scenario Questions
The following information applies to the questions below.
Several organisms, primarily protists, have what are called intermediate mitotic organization.
63) These protists are intermediate in what sense?
A) They reproduce by binary fission in their early stages of development and by mitosis when they are
mature.
B) They never coil up their chromosomes when they are dividing.
C) They use mitotic division but only have circular chromosomes.
D) They maintain a nuclear envelope during division.
E) None of them form spindles.
64) What is the most probable hypothesis about these intermediate forms of cell division?
A) They represent a form of cell reproduction which must have evolved completely separately from
those of other organisms.
B) They demonstrate that these species are not closely related to any of the other protists and may well
be a different kingdom.
C) They rely on totally different proteins for the processes they undergo.
D) They may be more closely related to plant forms that also have unusual mitosis.
E) They show some but not all of the evolutionary steps toward complete mitosis.
Use the following information to answer the questions below.
Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can therefore
be assayed to track their incorporation. In a set of experiments, a student—faculty research team used
labeled T nucleotides and introduced these into the culture of dividing human cells at specific times.
65) Which of the following questions might be answered by such a method?
A) How many cells are produced by the culture per hour?
B) What is the length of the S phase of the cell cycle?
C) When is the S chromosome synthesized?
D) How many picograms of DNA are made per cell cycle?
E) When do spindle fibers attach to chromosomes?
66) The research team used the setup to study the incorporation of labeled nucleotides into a culture of
lymphocytes and found that the lymphocytes incorporated the labeled nucleotide at a significantly
higher level after a pathogen was introduced into the culture. They concluded that
A) the presence of the pathogen made the experiment too contaminated to trust the results.
B) their tissue culture methods needed to be relearned.
C) infection causes lymphocytes to divide more rapidly.
D) infection causes cell cultures in general to reproduce more rapidly.
E) infection causes lymphocyte cultures to skip some parts of the cell cycle.
67) Once they had determined which cells were dividing, the team wanted to use a non-radioactive
method to track whether various physiological factors (such as food or body temperature) affect the
action of the pathogen. Which of the following would be effective, simple, and safe?
A) measuring picograms of DNA
B) measuring numbers of chromosomes
C) measuring numbers of chromatids
D) counting the frequency of cells in mitosis
E) counting newly formed plasma membranes
Use the following information to answer the questions below.
The research team established similar lymphocyte cultures from a number of human donors, including
healthy teenagers of both genders, patients already suffering from long-term bacterial infections, and
elderly volunteers. They found that the increase in lymphocyte incorporation after pathogen introduction
was slightly lower in some of the female teenagers and significantly lower in each of the elderly persons.
They repeated the study with a larger number of samples but got the same results.
68) What might be among the research team’s conclusions?
A) The young women showed these results because they have poorer nutrition.
B) The elderly persons’ samples demonstrated their lowered immune responses.
C) The young men had higher responses because they are generally healthier.
D) The patient samples should have had the lowest response but did not, so the experiment is invalid.
E) The elderly donor samples represent cells no longer capable of any cell division.
69) Which of the following investigations might be most productive to show what the data on the
teenagers might indicate?
A) test male teenagers
B) test teenagers who say they are not sexually active
C) test female teens at different times in their menstrual cycles
D) test relatives of the teens previously tested
E) test teenagers from different school systems
Use the following information to answer the questions below.
A student is looking through his light microscope (~450 X) at a squashed and stained onion root tip.
Some, but not all, of the cells have clearly visible chromosome strands.
70) When a cell is in anaphase of mitosis, which of the following will he see?
A) a clear area in the center of the cell
B) chromosomes clustered at the poles
C) individual chromatids separating
D) chromosomes clustered tightly at the center
E) formation of vesicles at the midline
71) When the cell has just completed telophase, which of the following does he see?
A) a clear area in the center of the cell
B) chromosomes clustered at the poles
C) individual chromatids separating
D) formation of vesicles at the midline
E) two small cells with chromatin
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 12
of the textbook.
72) 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) an animal cell in the process of cytokinesis.
B) a plant cell in the process of cytokinesis.
C) an animal cell in the S phase of the cell cycle.
D) a bacterial cell dividing.
E) a plant cell in metaphase.
73) Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the
assembly of microtubules, its effectiveness must be related to
A) disruption of mitotic spindle formation.
B) inhibition of regulatory protein phosphorylation.
C) suppression of cyclin production.
D) myosin denaturation and inhibition of cleavage furrow formation.
E) inhibition of DNA synthesis.
74) 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) cannot function properly because they are affected by density-dependent inhibition.
E) are always in the M phase of the cell cycle.
75) The decline of MPF activity at the end of mitosis is due to
A) the destruction of the protein kinase Cdk.
B) decreased synthesis of Cdk.
C) the degradation of cyclin.
D) the accumulation of cyclin.
E) synthesis of DNA.
76) In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
A) cells with more than one nucleus.
B) cells that are unusually small.
C) cells lacking nuclei.
D) destruction of chromosomes.
E) cell cycles lacking an S phase.
77) Which of the following does not occur during mitosis?
A) condensation of the chromosomes
B) replication of the DNA
C) separation of sister chromatids
D) spindle formation
E) separation of the spindle poles
78) 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) G1.
B) G2.
C) prophase.
D) metaphase.
E) anaphase.
79) The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell
cycle would be most disrupted by cytochalasin B?
A) spindle formation
B) spindle attachment to kinetochores
C) DNA synthesis
D) cell elongation during anaphase
E) cleavage furrow formation and cytokinesis