Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
32
If there are 20 sister chromatids in a cell, how many centromeres are there?
10
Which of the following is a true statement about sexual vs. asexual reproduction?
In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring
In eukaryotic cells, chromosomes are composed of _____.
DNA and proteins
Mitosis separates chromosomes. Cytoplasm is divided between two daughter cells by _____.
cytokinesis
Some cells have several nuclei per cell. How could such multinucleated cells be explained?
The cell underwent repeated mitosis, but cytokinesis did not occur
Which cytoskeletal proteins are important constituents of the contractile structures that form the cleavage furrows involved in animal cell cytokinesis?
actin
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
Myosin is a motor protein involved in animal cell cytokinesis. It binds to ATP or ADP, causing the myosin to move with respect to actin. What is the effect of the interaction between myosin and actin?
The cleavage furrow deepens
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?
prophase
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?
Golgi-derived vesicles
Movement of the chromosomes during anaphase would be most affected by a drug that prevents _____.
shortening of microtubules
During which phase of mitosis do the chromatids become chromosomes?
anaphase
The unlettered circle at the top of the figure shows a diploid
nucleus with four chromosomes that have not yet replicated. There are
two pairs of homologous chromosomes, one long and the other short. One
haploid set is black, and the other is gray. The circles labeled A to
E show various combinations of these chromosomes.
What is
the correct chromosomal condition at prometaphase of mitosis?
B
The unlettered circle at the top of the figure shows a diploid
nucleus with four chromosomes that have not yet replicated. There are
two pairs of homologous chromosomes, one long and the other short. One
haploid set is black, and the other is gray. The circles labeled A to
E show various combinations of these chromosomes.
What is
the correct chromosomal condition for one daughter nucleus at
telophase of mitosis?
E
If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next?
formation of telophase nuclei
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 _____
disruption of mitotic spindle formation
In the cells of some organisms, mitosis occurs without cytokinesis. This results in _____
cells with more than one nucleus
Which of the following does NOT occur during mitosis
replication of the DNA
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
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
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 _____.
centrosome
In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit _____
the attachment of microtubules to kinetochores
The mitotic spindle is a microtubular structure that is involved in _____.
separation of sister chromatids
Kinetochore microtubules assist in the process of splitting centromeres by _____
creating tension by pulling toward opposite poles
The product of the p53 gene _____.
inhibits the cell cycle
Researchers pulsed rapidly dividing cultured cells with radioactive thymidinefor 30 minutes. The cells were then exposed to a solution containing non-radiolabeled thymidine. Cells were analyzed at 2-hour intervals. At the 2-hour time point, no cells appeared to be dividing. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way:
There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division
Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1 1/2 times more DNA than G1 phase cells. The cells of this group are _____.
in the S phase of the cell cycle
The first gap in the cell cycle (G1) corresponds to _____
normal growth and cell function
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
G2
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?
16; 16
A cell in late anaphase of mitosis will have _____
no chromosomes in the center of the cell
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 _____.
metaphase
If a cell has accumulated DNA damage, it is unlikely to _____.
pass the G2 checkpoint
Regulatory proteins that prevent a cell from entering the S phase under conditions of DNA damage are also known as _____.
tumor suppressors
Proteins that are involved in the regulation of the cell cycle and that show fluctuations in concentration during the cell cycle are called _____
cyclins
The MPF protein complex turns itself off by _____
activating a process that destroys cyclin components
Cyclin-dependent kinase (Cdk) is _____
an enzyme that attaches phosphate groups to other proteins
Neurons and some other specialized cells divide infrequently because they _____.
have entered into G0
A cyclin _____
activates a Cdk molecule when it is in sufficient concentration
The following question are based on the accompanying
figure.
In the figure above, mitosis is
represented by which numbered part(s) of the cycle?
IV
The following question are based on the accompanying
figure.
In the figure above, G1 is
represented by which numbered part(s) of the cycle?
I or V
In the figure above, which number represents DNA synthesis?
II
In the figure above, which number represents the point in the cell cycle during which the chromosomes are replicated?
II
In the figure above, at which of the numbered regions would you expect to find cells at metaphase?
III only
In the figure above, MPF reaches its highest concentration during this stage
III
The data were obtained from a study of the length of time spent in
each phase of the cell cycle by cells of three eukaryotic organisms
designated beta, delta, and gamma.
Minutes
Spent in Cell Cycle Phases
Of the following,
the best conclusion concerning the difference between the S phases
for beta and gamma is that _____.
gamma contains more DNA than beta
The data were obtained from a study of the length of time spent in
each phase of the cell cycle by cells of three eukaryotic organisms
designated beta, delta, and gamma.
Minutes
Spent in Cell Cycle Phases
The best
conclusion concerning delta is that the cells _____
are in the G0 phase.
Nucleotides can be radiolabeled before they are incorporated into
newly forming DNA and, therefore, can be assayed to track their
incorporation. In a set of experiments, a student—faculty research
team used labeled T nucleotides and introduced these into the culture
of dividing human cells at specific times.
Which of the
following question might be answered by using the method described?
What is the length of the S phase of the cell cycle?
Nucleotides can be radiolabeled before they are incorporated into
newly forming DNA and, therefore, can be assayed to track their
incorporation. In a set of experiments, a student—faculty research
team used labeled T nucleotides and introduced these into the culture
of dividing human cells at specific times.
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
The decline of MPF activity at the end of mitosis is due to _____
the degradation of cyclin
Tumor-suppressor genes _____.
encode proteins that help prevent uncontrolled cell growth
BRCA1 and BRCA2 are considered to be tumor-suppressor genes because _____.
their normal products participate in repair of DNA damage
The cancer-causing forms of the Ras protein are involved in which of the following processes
relaying a signal from a growth factor receptor
Forms of the Ras protein found in tumors usually cause which of the following?
excessive cell division