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Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission?
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?
two long strands of DNA plus proteins
At which phase are centrioles beginning to move apart in animal cells?
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?
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
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 formation of the mitotic spindle.
Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?
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 did the nucleus contain 6 picograms of DNA?
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?
For anaphase to begin, which of the following must occur?
Cohesin must be cleaved enzymatically.
The chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules.
maintaining the region of overlap of microtubules in the cell's center
During which phase of mitosis do the chromatids become chromosomes?
how to use a hypotonic solution to swell nuclei
Which of the following is (are) required for motor proteins to function in the movement of chromosomes toward the poles of the mitotic spindle?
ATP as an energy source
What is a cleavage furrow?
a groove in the plasma membrane between daughter nuclei
Which of the following proteins are involved in binary fission as well as eukaryotic mitotic division?
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?
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 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?
A) The cells would immediately die.
What causes the decrease in the amount of cyclin at a specific point in the cell cycle?
Which of the following is released by platelets in the vicinity of an injury?
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?
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?
The cyclin component of MPF is destroyed toward the end of which phase?
Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called
The MPF protein complex turns itself off by
activating a process that destroys cyclin components.
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?
Which of the following is true concerning cancer cells?
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.
Which of the following describe(s) cyclin-dependent kinase (Cdk)?
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?
dinoflagellates and diatoms only
Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?
After which checkpoint is the cell first committed to continue the cell cycle through M?
Why do neurons and some other specialized cells divide infrequently?
They have been shunted into G0.
Which of the following most accurately describes a cyclin?
It activates a Cdk molecule when it is in sufficient concentration.
All cell cycle checkpoints are similar in which way?
They activate or inactivate other proteins.
At the M phase checkpoint, the complex allows for what to occur?
Separase enzyme cleaves cohesins and allows chromatids to separate.
What explains anchorage dependence of animal cells in vitro or in vivo?
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?
The cells show characteristics of tumors.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
It interferes with rapidly dividing cells.
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?
Karyotype samples to look for unusual size and number of chromosomes.
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.
What is the correct chromosomal condition at the prometaphase of mitosis?
What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?
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?
formation of telophase nuclei
In the figure above, mitosis is represented by which numbered part(s) of the cycle?
G1 is represented by which numbered part(s) of the cycle?
I or V
Which number represents DNA synthesis?
At which of the numbered regions would you expect to find cells at metaphase?
MPF reaches its threshold concentration at the end of this stage.
Use the data in Table 12.1 to answer the following questions.
Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that
The best conclusion concerning delta is that the cells
are actually in the G0 phase.
Several organisms, primarily protists, have what are called intermediate mitotic organization.
These protists are intermediate in what sense?
They maintain a nuclear envelope during division.
They show some but not all of the evolutionary steps toward complete mitosis.
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.
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?
counting the frequency of cells in mitosis
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.
What might be among the research team's conclusions?
The elderly persons' samples demonstrated their lowered immune responses.
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.
When a cell is in anaphase of mitosis, which of the following will he see?
a clear area in the center of the cell
When the cell has just completed telophase, which of the following does he see?
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 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
One difference between cancer cells and normal cells is that cancer cells
The decline of MPF activity at the end of mitosis is due to
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
Which of the following does not occur during mitosis?
separation of sister chromatids
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
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?
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