Chapter 12 Biology
DNA is replicated at this time of the cell cycl
S phase
The centromere is in the region which
chromatids remained attached to one another until anaphase
Movements of the chromosomes during anaphase would be most affected by a drug that
prevents shortening of microtubules
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis
10
If there are 20 chromatids in a cell, how many centromeres are there
10
If a cell has 8 chromosomes at metaphase of mitosis how many chromosomes during anaphase.
16
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 cell would have __ picograms at the end of the S phase and __ picograms at the end of G2
16:16
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with
2 nuclei
Starting with a fertilized egg(zygote), a series of five cell division would produce an early embryo with how many cells?
32
A cell containing 92 chromatids at metaphase of mitosis would, as it completion, produce two nuclei each containing how many chromosomes
46
Regarding mitosis an cytokinesis, one difference between higher plants and animals is that in plants
A cell plate begins to form at telophase, whereas in animals a clevage furrow is intiated at that stage
In the cell of some organisms, mitosis occurs without cytokinesis. This will results in
A cell with more than one nucleus.
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
The MPF protein complex turns itself off by
Activitating a process that destroys cyclin component
Density-dependent inhibition is explained by which of the following?
As cells become more numerous, the cell surface proteins of once cell contact the adjoining cell and they stop dividing.
Whcih of the following describe cyclin-dependent kinase (Cdk)
Both B and C are true. Cdk is present throughout the cell cycle and Cdk is an enzyme that attacted phosphate groups to other proteins
Which of the following is a protein maintain at constant level throughout the cell cycle that requires cyclin to become catytically active
Cdk
For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission.
Cell division would allow the orderly and efficient segregation of multiple linear chromosmes
Cells from an advanced miligant tumor mot often have very abnormal chromosomes and often an abnormal total number of chromosomes. Why might this occur?
Chromosomal abnormal cells can still go through cell cycle checkpoints
Proteins that are involved in the regulation of the cell cycle, and that show fluctionations in concentration during the cell cycle is called
Cyclins
In which group of eukaryotic organism does the nuclear envelop remain intact during mitosis
Dinoflagellates & diatoms
During which phases of mitosis are chromosomes composed of two chromatids?
From G2 of interphase through metaphase
Cells that are in a nondividiving stage are in which phase?
G0
Nerve and muscle cells are in this phase
G0 phase
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
The restriction point occurs here
G1 phase
Measurements of the amount of DNA per nucleus were taken on a large number of cells from a grouwing fungus. The measured DNA levels ranged rom 3 to 6 picograms per nucleus. In which stage of the cell was the nucleus with 6 picrograms of Dna
G2
Which of the following are primarily responsible for cytokinesis plant cells.
Golgi-derived vesicles
What causes the decrease in the amount of cyclin at a specific point in the cell cycle?
Its destruction by a process intiatied by the activity of its complex with a cyclin
An enzyme that attached a phosphate group to another molecule is called a
Kinase
The cyclin compoent of MPF is destroyed toward the end of this phase.
M phase
This is the shortest part of the cell cycle
M phase
Which of the following triggers the cells passage past the G2 checkpoint into mitosis
MPF
Which of the following best describes how chromosomes move towards the poles of the spindle during mitosis?
Motor proteins of the kinetochores move the chromosomes along the spindle of the microtubules.
Fibroblasts have receptors for this substance on their plasma membranes
PDGF
Which of the following is released by platelets i the vicinity of an injury?
PDGF
Which term describes cetrioles beginning to move apart in animal cells
Prophase
Which is a general term for enzymes that activite or inactivate other proteins by phosphorylating them?
Protein Kinase
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 cyclin E is highes during G1
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.
How do the daughter cells at the end the end of mitosis and cytokinesis compare with their parent cell when it was G1 of the cell cycle
The daughter cell have the same number of chromosomes and same amount of DNA
The reseach team establised similiar lymphocyte cultures from a number of human donors, including....
The elderly persons' samples demostrated their lower immune responses
Taxol is an anticancer drug extracted from Pacific yew tree. In animal cells, taxol distrups microtuble formation by binding microtubles and accelerating their assembly from the protein precursor, tublin. Suprisinlgy, this stops mitosis. Specifically, taox must affect
The fibers of the mitotic spindle
^ The research team used the setup to study the incorporation of lableed nucleotides into the culture of lymphocytes and found ht lymphoctyes incorpaorted the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. they concluded that
The infection casues cell cultures in general to reproduce more rapidly
These 'Protist' are intermediate in what sense
They maintain a nuclear envelop during division
What is the most probable hypothesis about these intermediate forms of cells division
They show some of the evolutionary steps toward complete mitosis but not all
Why do chromosomes coil during mitosis?
To allow the chromosomes to move without becoming entangled and breaking
Nucleotides can be raidolabled before they are incorporated into newly forming DNA and can therefore be assayed to track their incorporation. IN a set of experients, a student-faculaty reasearch team used labled T nucleotides to introduce these into the culture of dividein human cells at specific times. Which of the following questions might be answered by such a method
What is the lengt of the S phase of th cell cylce
Study the Graph. Note that G1 occurs at the plateus of the cell. Mitosis occurs occurs decline of the phase. The incline represents DNA synthesis and when chromosomes are replicated.
XX MPF reaches its threshold concentration at the end of this stage. (When it reaches it climaxx)
The formation of cell plate beginning across the middle of the cell and nuclei are re-forming at opposite ends of the cell. What kind of cells is this?
a plant cell undergoing cytokinesis
What is a chromatid
a replicated chromosome
Which term describes centromeres uncoupling, sister chromatid separating, and the new chromosomes moving to opposite poles of the cell
anaphase
Where do the microtubles of the sprindle originate during mitosis in both plant and animal
centrosome
The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most distrupted by cytochaslain B
clevaage furrow formation
IN order for anaphase to begin, which of the following must occur .
cohesin must be cleaved enzymatically
If mammalian cells receive a go-ahead signal at the G1 checkpoint they will rapidily
complete the cycle and divide
One difference between cancer cell and normal cells is that cancer cell
continue to divide even when they are tightly packed together.
A decline in MPF activity at the end of mitsosis is due to the..
degradation of cyclin
Vinblastine is a standard chemotherapeutic drug to treat cancer. Because it intergeres with the assembly of microtubules, its effectiveness must be related to
disruption of mitotic spindle formation
If the cell whose nuclear material is show in Figure 12.2 continues toward completion of mitosis, which of the following events would occur next?
formation of telophase nuclei
Besides the ability of some cancer cells to over-proliferate, what else could logically result in a tumor
lack of appropriate cell death
If the cells in the process of divided are subjected to colchicine, a drug that interferes with the function of the spindle apparatus, at which stage will mitosis be arrested.
metaphase
Imagine looking through a microscoope a squashed onion root tip. The chromosomes of many of the cell are plainly visible. In some cell, replicated chromosomes are aligned along the center of the cell. These particular cells are in which stage of mitosis
metaphase
Which is the longest in the mitotic stages
metaphase
The somatic cells derived from a single-cell zygote divide by which process
mitosis
Which term describes two centrosomes arrange at opposite poles
prometaphase
Chromosmes first become visible during which phase of mitosis?
prophase
Which of the following a protein synthesized at a specific times during the cell cycle that associates with a kinase to form a cataytically active complex
protein kinase
Which of the following does not occur during mitosis?
replication of DNA