The centromere is a region in which A) chromatids remain attached to one another until anaphase. B) metaphase chromosomes become aligned at the metaphase plate. C) chromosomes are grouped during telophase. D) the nucleus is located prior to mitosis. E) new spindle microtubules form at either end.
a
What is a chromatid? A) a chromosome in G1 of the cell cycle B) a replicate chromosome C) a chromosome found outside the nucleus D) a special region that holds two centromeres together E) another name for the chromosomes found in genetics
b
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells? A) 4 B) 8 C) 16 D) 32 E) 64
d
If there are 20 chromatids in a cell, how many centromeres are there? A) 10 B) 20 C) 30 D) 40 E) 80
a
For a newly evolving protist, what would be the advantage of using eukaryote -like cell division rather than binary fission? A) Binary fission would not allow for the formation of new organisms. B) Cell division would allow for the orderly and efficient segregation of multiple linear chromosomes. C) Cell division would be faster than binary fission. D) Cell division allows for lower rates of error per chromosome replication. E) Binary fission would not allow the organism to have complex cells.
b
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? A) The daughter cells have half the amount of cytoplasm and half the amount of DNA. B) The daughter cells have half the number of chromosomes and half the amount of DNA. C) The daughter cells have the same number of chromosomes and half the amount of DNA. D) The daughter cells have the same number of chromosomes and the same amount of DNA. E) The daughter cells have the same number of chromosomes and twice the amount of DNA.
d
Which term describes two centrosomes arranged at opposite poles of the cell? A) telophase B) anaphase C) prometaphase D) metaphase E) prophase
c
Which term describes centrioles beginning to move apart in animal cells? A) telophase B) anaphase C) prometaphase D) metaphase E) prophase
e
Which is the longest of the mitotic stages? A) telophase B) anaphase C) prometaphase D) metaphase E) prophase
d
Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell? A) telophase B) anaphase C) prometaphase D) metaphase E) prophase
b
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) anaphase B) prophase C) telophase D) metaphase E) interphase
d
A cell containing 92 chromatids at metaphase of mitosis would, at its completion, produce two nuclei each containing how many chromosomes? A) 12 B) 16 C) 23 D) 46 E) 92
d
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
d
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis? A) 10 B) 20 C) 30 D) 40 E) 80
b
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
d
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis? A) 10 B) 20 C) 30 D) 40 E) 80
b
If there are 20 chromatids in a cell at metaphase, how many chromosomes are there in each daughter cell following cytokinesis? A) 10 B) 20 C) 30 D) 40 E) 80
a
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 contains more RNA than gamma. D) gamma contains 48 times more DNA and RNA than beta. E) beta is a plant cell and gamma is an animal cell.
a
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.
d
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells? A) centromere B) centrosome C) centriole D) chromatid E) kinetochore
b
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase? A) 1 B) 2 C) 4 D) 8 E) 16
e
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with A) a single large nucleus. B) high concentrations of actin and myosin. C) two abnormally small nuclei. D) two nuclei. E) two nuclei but with half the amount of DNA.
d
Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants A) the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils. B) sister chromatids are identical, but they differ from one another in animals. C) a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated at that stage. D) chromosomes become attached to the spindle at prophase, whereas in animals chromosomes do not become attached until anaphase. E) spindle poles contain centrioles, whereas spindle poles in animals do not.
c
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) an animal cell in metaphase B) an animal cell in telophase C) an animal cell undergoing cytokinesis D) a plant cell in metaphase E) a plant cell undergoing cytokinesis
e
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 fibers of the mitotic spindle. B) anaphase. C) formation of the centrioles. D) chromatid assembly. E) the S phase of the cell cycle.
a
Which of the following are primarily responsible for cytokinesis in plant cells? A) kinetochores B) Golgi-derived vesicles C) actin and myosin D) centrioles and basal bodies E) cyclin-dependent kinases
b
Chromosomes first become visible during which phase of mitosis? A) prometaphase B) telophase C) prophase D) metaphase E) anaphase
c
During which phases of mitosis are chromosomes composed of two chromatids? A) from interphase through anaphase B) from G1 of interphase through metaphase C) from metaphase through telophase D) from anaphase through telophase E) from G2 of interphase through metaphase
e
In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis? A) seedless plants B) dinoflagellates C) diatoms D) B and C only E) A, B, and C
d
Movement of the chromosomes during anaphase would be most affected by a drug that A) reduces cyclin concentrations. B) increases cyclin concentrations. C) prevents elongation of microtubules. D) prevents shortening of microtubules. E) prevents attachment of the microtubules to the kinetochore.
d
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? A) G0 B) G1 C) S D) G2 E) M
d
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 G2. A) 8; 8 B) 8; 16 C) 16; 8 D) 16; 16 E) 12; 16
d
The somatic cells derived from a single-celled zygote divide by which process? A) meiosis B) mitosis C) replication D) cytokinesis alone E) binary fission
b
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? A) telophase B) prophase C) anaphase D) metaphase E) prometaphase
d
In order for anaphase to begin, which of the following must occur? A) Chromatids must lose their kinetochores. B) Cohesin must attach the sister chromatids to each other. C) Cohesin must be cleaved enzymatically. D) Kinetochores must attach to the metaphase plate. E) Spindle microtubules must begin to depolymerize.
c
Why do chromosomes coil during mitosis? A) to increase their potential energy B) to allow the chromosomes to move without becoming entangled and breaking C) to allow the chromosomes to fit within the nuclear envelope D) to allow the sister chromatids to remain attached E) to provide for the structure of the centromere
b
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.
d
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 of the evolutionary steps toward complete mitosis but not all.
e
Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis? A) The chromosomes are ʺreeled inʺ by the contraction of spindle microtubules. B) Motor proteins of the kinetochores move the chromosomes along the spindle microtubules. C) Non-kinetochore spindle fibers serve to push chromosomes in the direction of the poles. D) both A and B E) A, B, and C
b
Which of the following is a function of those spindle microtubules that do not attach to kinetochores? A) maintaining an appropriate spacing among the moving chromosomes B) producing a cleavage furrow when telophase is complete C) providing the ATP needed by the fibers attached to kinetochores D) maintaining the region of overlap of fibers in the cellʹs center E) pulling the poles of the spindles closer to one another
d
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?
b
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.
c
If mammalian cells receive a go-ahead signal at the G1 checkpoint, they will A) move directly into telophase. B) complete the cycle and divide. C) exit the cycle and switch to a nondividing state. D) show a drop in MPF concentration. E) complete cytokinesis and form new cell walls.
b
Cells that are in a nondividing state are in which phase? A) G0 B) G2 C) G1 D) S E) M
a
What causes the decrease in the amount of cyclin at a specific point in the cell cycle? A) an increase in production once the restriction point is passed B) the cascade of increased production once its protein is phosphorylated by Cdk C) the changing ratio of cytoplasm to genome D) its destruction by a process initiated by the activity of its complex with a cyclin E) the binding of PDGF to receptors on the cell surface
d
Which of the following is released by platelets in the vicinity of an injury? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk
a
Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk
c
Fibroblasts have receptors for this substance on their plasma membranes: A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk
a
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? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk
d
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk
e
Which of the following triggers the cellʹs passage past the G2 checkpoint into mitosis? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk
b
This is the shortest part of the cell cycle: A) G0 B) G1 C) S D) G2 E) M
e
DNA is replicated at this time of the cell cycle: A) G0 B) G1 C) S D) G2 E) M
c
The ʺrestriction pointʺ occurs here: A) G0 B) G1 C) S D) G2 E) M
b
Nerve and muscle cells are in this phase: A) G0 B) G1 C) S D) G2 E) M
a
The cyclin component of MPF is destroyed toward the end of this phase: A) G0 B) G1 C) S D) G2 E) M
e
In the figure above, mitosis is represented by which number? A) I B) II C) III D) IV E) V
d
G1 is represented by which number(s)? A) I and V B) II and IV C) III D) IV E) V
a
Which number represents DNA synthesis? A) I B) II C) III D) IV E) V
b
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
b
MPF reaches its threshold concentration at the end of this stage. A) I B) II C) III D) IV E) V
c
An enzyme that attaches a phosphate group to another molecule is called a A) phosphatase. B) phosphorylase. C) kinase. D) cyclase. E) ATPase.
c
Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called A) ATPases. B) kinetochores. C) centrioles. D) proton pumps. E) cyclins.
e
The MPF protein complex turns itself off by A) activating a process that destroys cyclin component. B) activating an enzyme that stimulates cyclin. C) binding to chromatin. D) exiting the cell. E) activating the anaphase-promoting complex.
a
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? A) The cell would prematurely enter anaphase. B) The cell would never leave metaphase. C) The cell would never enter metaphase. D) The cell would never enter prophase. E) The cell would undergo normal mitosis, but fail to enter the next G1 phase.
e
Density-dependent inhibition is explained by which of the following? A) As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce control factors. B) As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing. C) As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor. D) As cells become more numerous, more and more of them enter the S phase of the cell cycle. E) As cells become more numerous, the level of waste products increases, eventually slowing down metabolism.
b
Which of the following is true concerning cancer cells? A) They do not exhibit density-dependent inhibition when growing in culture. B) When they stop dividing, they do so at random points in the cell cycle. C) They are not subject to cell cycle controls. D) B and C only E) A, B, and C
e
Which of the following describe(s) cyclin-dependent kinase (Cdk)? A) Cdk is inactive, or ʺturned off,ʺ in the presence of cyclin. B) Cdk is present throughout the cell cycle. C) Cdk is an enzyme that attaches phosphate groups to other proteins. D) Both A and B are true. E) Both B and C are true.
e
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? A) The amount of cyclin E is greatest during the S phase. B) The amount of Cdk 2 is greater during G1 compared to the S phase. C) The amount of cyclin E is highest during G1. D) The amount of Cdk 2 is greatest during G1. E) The activity of the cyclin E/Cdk 2 complex is highest during G2.
c
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 women 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 their conclusions? A) The young women showed these results because they have poorer nutrition. B) The elderly personsʹ samples demonstrated their lowered immune responses. C) The young men had higher response 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.
b
Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur? A) Cancer cells are no longer density dependent. B) Cancer cells are no longer anchorage dependent. C) Chromosomally abnormal cells can still go through cell cycle checkpoints. D) Chromosomally abnormal cells still have normal metabolism. E) Transformation introduces new chromosomes into cells.
c
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor? A) metastasis B) changes in the order of cell cycle stages C) lack of appropriate cell death D) inability to form spindles E) inability of chromosomes to meet at the metaphase plate
c
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) 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.
b
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.
a
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.
a
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.
c
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 cyclin. C) the degradation of cyclin. D) synthesis of DNA. E) an increase in the cellʹs volume-to-genome ratio.
c
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
e
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.
a
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
b