Chapter 12 Biology 111
what follows cell fusion of mitotic cells with cells in G2 phase
chromosomes of the G2 cells condense prematurely
8) If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
A) 10
chromosomes first become visible during which phase of mitosis
prophase
how many different checkpoints are there in the mechanical analogy for the cell cycle control system
3
43) After which checkpoint is the cell first committed to continue the cell cycle through M?
B) G1
3) If there are 20 chromatids in a cell, how many centromeres are there?
A) 10
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.
29) Which of the following is released by platelets in the vicinity of an injury?
A) PDGF
47) At the M phase checkpoint, the complex allows for what to occur?
A) Separase enzyme cleaves cohesins and allows chromatids to separate.
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
35) The MPF protein complex turns itself off by
A) activating a process that destroys cyclin components.
76) In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
A) cells with more than one nucleus.
1) The centromere is a region in which
A) chromatids remain attached to one another until anaphase.
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.
21) Which of the following was a discovery that had to be made before human chromosomes could be correctly counted?
A) how to use a hypotonic solution to swell nuclei
26) You have the technology necessary to measure each of the following in a sample of animal cells: chlorophylls, organelle density, picograms of DNA, cell wall components, and enzymatic activity. Which would you expect to increase significantly from M to G1?
A) organelle density and enzymatic activity
20) During which phase of mitosis do the chromatids become chromosomes?
A) telophase
10) Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, Taxol must affect
A) the formation of the mitotic spindle.
75) The decline of MPF activity at the end of mitosis is due to
C) the degradation of cyclin.
37) Density-dependent inhibition is explained by which of the following?
B) As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.
4) For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission?
B) Cell division would allow for the orderly and efficient segregation of multiple linear chromosomes.
11) Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?
B) Golgi-derived vesicles
32) Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?
B) MPF
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?
B) The elderly persons' samples demonstrated their lowered immune responses.
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
B) a plant cell in the process of cytokinesis.
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?
B) What is the length of the S phase of the cell cycle?
9) Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
B) centrosome
77) Which of the following does not occur during mitosis?
B) replication of the DNA
48) What explains anchorage dependence of animal cells in vitro or in vivo?
B) response of the plasma membrane to cell cycle controls
17) Why do chromosomes coil during mitosis?
B) to allow the chromosomes to move without becoming entangled and breaking
41) Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?
C) Chromosomally abnormal cells can still go through cell cycle checkpoints.
16) For anaphase to begin, which of the following must occur?
C) Cohesin must be cleaved enzymatically.
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?
C) Karyotype samples to look for unusual size and number of chromosomes.
40) A particular cyclin called cyclin E forms a complex with Cdk 2 (cyclin-dependent kinase 2). This complex is important for the progression of the cell from G1 into the S phase of the cell cycle. Which of the following statements is correct?
C) The amount of free cyclin E is highest during G1.
27) A plant-derived protein known as colchicine can be used to poison cells by blocking the formation of the spindle. Which of the following would result if colchicine is added to a sample of cells in G2?
C) The chromosomes would coil and shorten but have no spindle to which to attach.
44) Why do neurons and some other specialized cells divide infrequently?
C) They have been shunted into G0.
23) What is a cleavage furrow?
C) a groove in the plasma membrane between daughter nuclei
74) One difference between cancer cells and normal cells is that cancer cells
C) continue to divide even when they are tightly packed together.
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. 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
C) infection causes lymphocytes to divide more rapidly.
42) Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
C) lack of appropriate cell death
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. 69) Which of the following investigations might be most productive to show what the data on the teenagers might indicate?
C) test female teens at different times in their menstrual cycles
15) A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2?
D) 16; 16
2) Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
D) 32
22) Which of the following is (are) required for motor proteins to function in the movement of chromosomes toward the poles of the mitotic spindle?
D) ATP as an energy source
14) Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?
D) G2
45) Which of the following most accurately describes a cyclin?
D) It activates a Cdk molecule when it is in sufficient concentration.
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?
D) The cells show characteristics of tumors.
18) Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?
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.
Several organisms, primarily protists, have what are called intermediate mitotic organization. 63) These protists are intermediate in what sense?
D) They maintain a nuclear envelope during division.
24) Which of the following proteins are involved in binary fission as well as eukaryotic mitotic division?
D) actin and tubulin
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. 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?
D) counting the frequency of cells in mitosis
30) Which of the following is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex?
D) cyclin
12) In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?
D) dinoflagellates and diatoms only
28) What causes the decrease in the amount of cyclin at a specific point in the cell cycle?
D) its destruction by a process initiated by the activity of its complex with a cyclin
19) Which of the following is a function of those spindle microtubules that do not attach to kinetochores?
D) maintaining the region of overlap of microtubules in the cell's center
7) If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested?
D) metaphase
13) Movement of the chromosomes during anaphase would be most affected by a drug that
D) prevents shortening of microtubules.
25) Using which of the following techniques would enable your lab group to distinguish between a cell in G2 and a cell from the same organism in G1?
D) radioactive-labeled nucleotides
5) Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal) nucleus. It might consist of which of the following?
D) two long strands of DNA plus proteins
31) Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
E) Cdk
39) Which of the following describe(s) cyclin-dependent kinase (Cdk)?
E) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.
50) For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
E) It interferes with rapidly dividing cells.
33) The cyclin component of MPF is destroyed toward the end of which phase?
E) M
36) 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?
E) The cell would undergo normal mitosis, but fail to enter the next G1 phase.
46) All cell cycle checkpoints are similar in which way?
E) They activate or inactivate other proteins.
Several organisms, primarily protists, have what are called intermediate mitotic organization. 64) What is the most probable hypothesis about these intermediate forms of cell division?
E) They show some but not all of the evolutionary steps toward complete mitosis.
38) Which of the following is true concerning cancer cells?
E) When they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.
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?
E) cleavage furrow formation and cytokinesis
34) Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called
E) cyclins.
6) At which phase are centrioles beginning to move apart in animal cells?
E) prophase
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. 71) When the cell has just completed telophase, which of the following does he see?
E) two small cells with chromatin
at which checkpoint does MPF act?
G2
which of the following phases of the cell cycle does not have a checkpoint
S
what is a mitotic checkpoint
a control point in the cell cycle where STOP signals are overridden by GO signals
in regard to the molecular basis of the cell cycle contralto the G2 checkpoint, which of the following best describes the mitosis promoting factor (MPF)
a dimer composed of cyclin and Cdk
which term describes centromeres uncoupling sister chromatids separating and the 2 new chromosomes moving to opposite poles of the cell
anaphase
what is the proper term for the region of a duplicated chromosomes that holds the sister chromatids together
centromere
during which phases of mitosis are chromosomes composed of two chromatids
from G2 of interphase through metaphase
in regard to the G1 checkpoint what happens to a cell that does not receive a go ahead signal
it goes into Go
in regard to the g2 checkpoint what happens to cyclin during g2 and s phase
it increases in amount
when during the cell cycle does Cdk reach its peak amount
it remains constant throughout the cell cycle
in regard to the fluctuation of MPF activity and cyclin concentration during the cell cycle how does the amount of Cdk vary during the various stages of the cell cycle
its amount remains constant during the cell cycle
in the mitotic division of an animal cell, during which stage is the nuclear envelope totally gone
metaphase
when during the cell cycle does cyclin reach its peak amount
mitosis
what is the result of fusing a cell in M phase with a cell in G1 phase
onset of mitosis in the G1 phase cell
which of the following stages of mitosis is characterized by a fragmented nuclear envelope centrosomes at opposite poles and the presence of both types of spindle microtubules
prometaphase
during anaphase of mitosis kinetochore microtubules were shown to
shorten at the kinetochore ends
what follows cell fusion of mitotic cells with cells in G1 phase
the chromosomes of the G1 cells condense prematurely
what is a kinetochore
the protein structure at the centromere region that attaches to microtubules
which of the following statements were proven by cell fusion experiments, in which cells in different stages of mitosis were fused
there are molecular signals in the cytoplasm that regulate the cell cycle
cytokinesis usually but not always follows mitosis. if a cell completed mitosis but not cytokinesis, the result would be a cell
with two nuclei