Ch 12 Flashcards
The centromere is a region in which
A) chromatids remain attached to one another until anaphase
What is a chromatid?
b) a replicate chromosome
A series of five cell divisions would produce an early embryo with how many cells?
D) 32
If there are 20 chromatids in a cell, how many centromeres are there?
A) 10
What would be the advantage of using eukaryote type cell division rather than binary fission?
B) 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?
D) The daughter cells have the same number of chromosomes and same amount of DNA.
Which term describes two centrosomes arranged at opposite poles of the cell?
C) prometaphase
Which term describes centrioles beginning to move apart in animal cells?
E) Prophase
Which is the longest of the mitotic stages?
D) metaphase
Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?
B) anaphase
If the cells in the process of dividing are subjected to colchicine, a drug the interferes with the functioning of the spindle apparatus, at which stage will mitosis be arrested?
D) metaphase
A cell containing 92 chromatids at metaphase would, at its completion, produce two nuclei containing how many chromosomes?
D) 46
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
B) 20
If there are 20 chromatids in a cell at metaphase, how may chromosomes are there in each daughter cell following cytokinesis?
A) 10
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
B) centrosome
If a cell has 8 chromosomes at metaphase of mitosis, how many chromosomes will it have during anaphase?
E) 16
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the results would be a cell with
D) two nuclei
Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants….
C) a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated.
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?
E) 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….
A) the fibers of the mitotic spindle
Which of the following are primarily responsible for cytokinesis in plant cells?
B) Golgi-derived vesicles
Chromosomes first become visible during which phase of mitosis?
C) prophase
During which phases of mitosis are chromosomes composed of two chromatids?
E) from G2 of interphase through metaphase
In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?
D) dinoflagellates and diatoms
Movement of the chromosomes during anaphase would be most affected by a drug that
D)prevents the 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 pictograms per nucleus. In which stage of the cell cycle was the nucleus with 6 pictograms of DNA?
D)G2
A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 per nucleus. Those cells would have _____ pictograms at the end of the Sphase and _____ pictograms at the end ofG2.
D) 16,16
The somatic cells derived from a single celled zygote divide by which process?
B) mitosis
Looking at an onion root tip. The chromosomes of many of the cells are plainly visble. In some cells, replaticated chromosomes are alined along the center of the cell. These cells are in which stage of mitosis?
D) metaphase
In order for anaphase to begin, which of the following must occur?
C) cohesion must be cleaved enzymatically
Why do chromosomes coil during mitosis?
B) to allow the chromosomes to move without becoming entangled and breaking
These protists are intermediate in what sense?
D) They maintain a nuclear envelope during division.
What is the most probable hypothesis about these intermediate forms of cell division?
E) 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?
B) 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 the kinetochores?
D) maintaining the region of overlap of fibers in the cell’s center
If mammalian cells receive a go ahead signal at the G1 checkpoint, they will
B) complete the cycle and divide
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
Which of the following is released by platelets in the vicinity of an injury?
A) PDGF
Which is a general term for enzymes that activate or inactivate other proteins by phosphorylating them?
C) protein kynase
Fibroblasts have receptors for this substance on their plasma membranes:
A)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?
D) Cyclin
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
E) CDK
Which of the following triggers the cell’s passage past the G2 checkpoint into mitosis?
B) MPF
This is the shortest part of the cell cycle:
E) M
DNA is replicated at this time of the cell cycle:
C) S
The restriction point occurs here:
B) G1
Nerve and muscle cells are in this phase:
A) G0
The cyclin component of MPF is destroyed toward the end of this phase:
E) M
An enzymes that attaches a phosphate group to another molecule is called a
C) Kinase
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
The MPF protein complex turns itself off by
A) activating by 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?
E) The cell would no longer undergo normal, mitosis, but fail to enter the next G1 phase.
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.
Which of the following is true concerning cancer cells?
E) don’t exhibit density dependent inhibition, stop dividing at random points in the cells cycle, not subject to cell cycle controls
Which of the following describes cyclin dependent kinase (Cdk)?
E) CDK is an enzyme that attaches phosphate groups to other proteins. CDK is present throughout cell cycle.
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
C) The amount of cyclin E is highest during G1
Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal number. Why might this occur?
C) Chromosomally abnormal cells can still go thru cell cycle checkpoints.
Besides the ability of some cancer cells to proliferate, what else could logically result in a tumor?
C) Lack of appropriate cell death
Thru a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei reforming on either side of the cell plate. This cell is most likely
B) a plant cell in 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
A) disruption of mitotic spindle formation
A particular cell has half as much DNA as some other cells in a mitiotically active tissue. The cell in question is most likely in
A) G1
One difference between cancer cells and normal cells is that cancer cells
C) continue to divide even when they are tightly packed together
The decline of MPF activity at the end of mitosis is due to
C) 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?
E) cleavage furrow formation
In the cell of some organisms, mitosis occurs without cytokinesis. This will result in
A)cells with more than one nucleus
Which of the following does now occur during mitosis?
B) replication of DNA
