Chapter 12 Test Flashcards
The centromere is a region in which
chromatids remain attached to one another until anaphase.
What is a chromatid?
a replicate chromosome
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
32
If there are 20 chromatids in a cell, how many centromeres are there?
10
For a newly evolving protist, what would be the advantage of using eukaryote -like cell division rather than binary fission?
Cell division would allow for the orderly and efficient segregation of multiple linear chromosomes.
How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?
The daughter cells have the same number of chromosomes and the same amount of DNA.
at prometaphase of mitosis
B
one daughter nucleus at telophase of mitosis
E
Which term describes two centrosomes arranged at opposite poles of the cell?
prometaphase
Which term describes centrioles beginning to move apart in animal cells?
prophase
Which is the longest of the mitotic stages?
metaphase
Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?
anaphase
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle apparatus, at which stage will mitosis be arrested?
metaphase
A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes?
46
If the cell whose nuclear material is shown in Figure 12.2 continues toward completion of mitosis, which of the following events would occur nex
formation of telophase nuclei
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
20
If there are 20 chromatids in a cell at metaphase, how many chromosomes are there in each daughter cell following cytokinesis?
10
Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that
gamma contains more DNA than beta.
The best conclusion concerning delta is that the cells
are actually in the G0 phase.
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
centrosome
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?
16
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with
two nuclei.
Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants
a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated at that stage.
The formation of a cell plate is beginning across the middle of a cell and nuclei are re-forming at opposite ends of the cell. What kind of cell is this?
a plant cell undergoing cytokinesis
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
the fibers of the mitotic spindle.
Which of the following are primarily responsible for cytokinesis in plant cells?
Golgi-derived vesicles
Chromosomes first become visible during which phase of mitosis?
prophase
During which phases of mitosis are chromosomes composed of two chromatids?
from G2 of interphase through metaphase
In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?
B and C only
Movement of the chromosomes during anaphase would be most affected by a drug that
prevents shortening of microtubules.
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 was the nucleus with 6 picograms of DNA?
G2
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. Those cells would have __________ picograms at the end of the S phase and __________ picograms at the end of G 2.
16; 16
The somatic cells derived from a single-celled zygote divide by which process?
mitosis
Imagine looking through a microscope at a squashed onion root tip. The chromosomes of many of the cells are plainly visible. In some cells, replicated chromosomes are aligned along the center (equator) of the cell. These particular cells are in which stage of mitosis?
metaphase
In order for anaphase to begin, which of the following must occur?
Cohesin must be cleaved enzymatically.
Why do chromosomes coil during mitosis?
to allow the chromosomes to move without becoming entangled and breaking
These Protists are intermediate in what sense?
They maintain a nuclear envelope during division.
What is the most probable hypothesis about these intermediate forms of cell division?
They show some of the evolutionary steps toward complete mitosis but not all.
Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?
Motor proteins of the kinetochores move the chromosomes along the spindle microtubules.
Which of the following is a function of those spindle microtubules that do not attach to kinetochores?
maintaining the region of overlap of fibers in the cellʹs center
Which of the following questions might be answered by such a method?
What is the length of the S phase of the cell cycle?
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
infection causes lymphocytes to divide more rapidly.
If mammalian cells receive a go-ahead signal at the G1 checkpoint, they will
complete the cycle and divide.
Cells that are in a nondividing state are in which phase?
G0
What causes the decrease in the amount of cyclin at a specific point in the cell cycle?
its destruction by a process initiated by the activity of its complex with a cyclin
Which of the following is released by platelets in the vicinity of an injury?
PDGF
Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?
protein kinase
Fibroblasts have receptors for this substance on their plasma membranes:
PDGF
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?
cyclin
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
Cdk
Which of the following triggers the cellʹs passage past the G2 checkpoint into mitosis?
MPF
This is the shortest part of the cell cycle:
M
DNA is replicated at this time of the cell cycle:
S
The ʺrestriction pointʺ occurs here:
G1
Nerve and muscle cells are in this phase:
G0
The cyclin component of MPF is destroyed toward the end of this phase:
M
In the figure above, mitosis is represented by which number?
IV
G1 is represented by which number(s)?
I and V
Which number represents DNA synthesis?
II
Which number represents the point in the cell cycle during which the chromosomes are replicated?
II
MPF reaches its threshold concentration at the end of this stage.
III
An enzyme that attaches a phosphate group to another molecule is called a
kinase.
Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called
cyclins.
The MPF protein complex turns itself off by
activating a process that destroys cyclin component.
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?
The cell would undergo normal mitosis, but fail to enter the next G1 phase.
Density-dependent inhibition is explained by which of the following?
As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.
Which of the following is true concerning cancer cells?
A, B, and C
Which of the following describe(s) cyclin-dependent kinase (Cdk)?
Both B and C are true.
A particular cyclin called cyclin E forms a complex with a cyclin-dependent kinase called Cdk 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?
The amount of cyclin E is highest during G1.
They repeated the study with a larger number of samples but got the same results. What might be among their conclusions?
The elderly personsʹ samples demonstrated their lowered immune responses.
Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?
Chromosomally abnormal cells can still go through cell cycle checkpoints.
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
lack of appropriate cell death
Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei re-forming on either side of the cell plate. This cell is most likely
a plant cell in the process of cytokinesis.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to
disruption of mitotic spindle formation.
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
G1
One difference between cancer cells and normal cells is that cancer cells
continue to divide even when they are tightly packed together.
The decline of MPF activity at the end of mitosis is due to
the degradation of cyclin.
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?
cleavage furrow formation
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
cells with more than one nucleus.
Which of the following does not occur during mitosis?
replication of the DN
