Chapter 12 Practice Test Questions
In eukaryotic cells, chromosomes are composed of
DNA and proteins
What is the final result of mitosis in a human sell
genetically identical 2n somatic cells
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells
If there are 20 duplicated chromosomes in a cell how many centromeres are there
Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1.5 times more DNA than G1 phase cells. The cells of this group are
in the S phases of the cell cycle
The first gap in the cell cycle G1 corresponds to
normal growth and cell function
The microtubule-organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle. Specifically, it is known as the
In humankind many other eukaryotic species’ cells, the nuclear membrane has to disappear to permit
the attachment of microtubules to kinetochores
The mitotic spindle is a micro tubular structure that is involved in
separation of sister chromatids
Metaphase is characterized by
aligning of chromosomes on the equator
Kinetochore microtubules assist in the process of splitting centromere by
creating tension by pulling toward opposite poles
Some cells have several nuclei per cell. How could such multinucleate cells be explained?
the cell underwent repeated mitosis, but cytokinesis did not occur
How is plant cell cytokinesis different from animal cell cytokinesis
Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to _____.
the cleavage furrow of eukaryotic animal cells
At which phase are centrioles beginning to move apart in animal cells?
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation. Surprisingly, this stops mitosis. Specifically, Taxol must affect _____.
the structure of the mitotic spindle
Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?
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 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?
The beginning of anaphase is indicated by which of the following?
Cohesin is cleaved enzymatically.
During which phase of mitosis do the chromatids become chromosomes?
A cleavage furrow is _____.
groove in the plasma membrane between daughter nuclei
The research team used their experiments 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
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
Which of the following does NOT occur during mitosis?
replication of the DNA
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 and cytokinesis
Motor proteins require which of the following to function in the movement of chromosomes toward the poles of the mitotic spindle?
ATP as an energy source
Neurons and some other specialized cells divide infrequently because they _____.
have entered into G0
MPF is a dimer consisting of _____.
cyclin and a cyclin-dependent kinase
Cyclin-dependent kinase (Cdk) is _____.
an enzyme that attaches phosphate groups to other proteins
What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2?
The cells enter mitosis.
Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis?
The cyclin component of MPF is degraded.
The M-phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in _____.
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 steady 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?
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.
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
lack of appropriate cell death
Anchorage dependence of animal cells in vitro or in vivo depends on which of the following?
response of the cell cycle controls to signals from the plasma membrane
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.
Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities?
Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
Exposure of zebrafish nuclei to meiotic cytosol resulted in phosphorylation of NEP55 and L68 proteins by cyclin-dependent kinase 2. NEP55 is a protein of the inner nuclear membrane, and L68 is a protein of the nuclear lamina. What is the most likely role of phosphorylation of these proteins in the process of mitosis?
They are involved in the disassembly of the nuclear envelope.
Density-dependent inhibition is a phenomenon in which crowded cells stop dividing at some optimal density and location. This phenomenon involves binding of a cell-surface protein to its counterpart on an adjoining cell’s surface. A growth inhibiting signal is sent to both cells, preventing them from dividing. Certain external physical factors can affect this inhibition mechanism.
As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.
The centromere is a region in which
chromatids remain attached to one another until anaphase.
What is a chromatid?
a replicate chromosome
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
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
Which term describes centrioles beginning to move apart in animal cells?
Which is the longest of the mitotic stages?
Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?
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?
A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes?
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with
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.
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.
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?
dinoflagellates and diatoms
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?
In order for anaphase to begin, which of the following must occur?
Cohesin must be cleaved enzymatically.
Why do chromosomes coil during mitosis?
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