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
answer
a plant cell in the process of cytokinesis.
question
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of micro-tubules, its effectiveness must be related to
answer
disruption of mitotic spindle formation.
question
One difference between cancer cells and normal cells is that cancer cells
answer
continue to divide even when they are tightly packed together.
question
The decline of MPF activity at the end of mitosis is due to
answer
the degradation of cyclin.
question
In the cells of some organisms, mitosis occurs without cytoki-nesis. This will result in
answer
cells with more than one nucleus.
question
Which of the following does not occur during mitosis?
answer
replication of the DNA
question
What is true of all cancers?
answer
They have escaped normal cell cycle controls.
question
How do cancer cells differ from normal cells?
answer
Cancer cells may be immortal.
question
The cell cycle control systems of cancer cells differ from those of normal cells. Select the best explanation for this fact.
answer
Genetic changes alter the function of the cancer cell's protein products.
question
If a eukaryotic cell is in the G1 phase of the cell cycle, which statement about the cell's chromosomes must be correct?
answer
Each chromosome is made of a complex of DNA and associated proteins.
question
Which statement provides the best description of the interphase portion of the cell cycle?
answer
During interphase, a cell is metabolically active.
question
An environmental substance that is known to cause cancer is called a what?
answer
carcinogen
question
Radiation emitted from which of the following two sources are most alike?
answer
microwaves and cellphones
question
You are trying to discover if the pesticide atrazine is a mutagen. Where are you looking for mutations?
answer
DNA
question
Which of the following is true?
answer
Cancer-causing substances work in many different ways.
question
Which of the following best summarizes current scientific opinion regarding cellphones and brain cancer?
answer
While most studies indicate that cellphones do not cause brain cancer, more research needs to be done as cellphone use increases.
question
Which of the following codes for proteins?
answer
genes
question
You are developing a new drug that damages the cells that provide the supportive structure required by a tumor. Which type of cell are you targeting?
answer
fibroblast
question
A tumor would not be able to have its own blood supply if it weren't for which of the following?
answer
endothelial cells
immune system cells
question
Which of the following appears to be true according to current research?
answer
As the population of Helicobacter pylori decreases in the human body, cases of esophageal cancer increase.
question
Can you match these prefixes, suffixes, and word roots with their definitions?
Prior to this new technique, how were mice given cancerous tumors?
answer
The tumors were implanted under the skin.
question
You are an oncologist. A patient presents with advanced prostate cancer and you follow standard protocol. What do you do?
answer
The patient is treated with chemical castration.
question
You are an endocrinologist studying new treatments for prostate cancer. You have a patient with an unusually large level of dihydrotestosterone. Which of the following is true?
answer
Your patient's cancer has become resistant to the standard treatment.
question
Which of the following is true regarding prostate cancer cells?
answer
They can activate and inactivate certain genes.
question
Your uncle has prostate cancer. Which of the following indicates improvement in his condition?
answer
A decreasing PSA.
question
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
answer
G1
question
The drug cytochalasin B blocks the function of actin. Which of the following aspects of the animal cell cycle would be most disrupted by cytochalasin B?
answer
cleavage furrow formation and cytokinesis
question
Which of the following is a large reason behind the increase in breast cancer in developing countries?
answer
Women are living longer.
question
Which of the following is true?
answer
Worldwide, breast cancer is the most common cancer in women, and the largest cancer killer of women.
question
You are an oncologist specializing in colon cancer. A patient presents to you with disease that has spread to his bones and liver and there is no treatment available. What stage cancer is this?
answer
4
question
A woman in Uganda is diagnosed with breast cancer. If any treatment is done, what is it most likely to be?
answer
Only a mastectomy.
question
You are a breast cancer survivor and advocate in the U.S. Why do you promote self breast exams to women under 50 rather than annual mammograms?
answer
Women under 50 tend to have denser breast tissue which often make mammograms inconclusive.
question
Why do some species employ both mitosis and meiosis, whereas other species use only mitosis?
answer
They need both if they are producing animal gametes.
question
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain?
answer
92
question
Why is it difficult to observe individual chromosomes with a light microscope during interphase?
answer
They have uncoiled to form long, thin strands.
question
In eukaryotic cells, chromosomes are composed of _____.
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
answer
32
question
If there are 20 duplicated chromosomes in a cell, how many centromeres are there?
answer
20
question
As in most areas of biology, the study of mitosis and the cell cycle involves a lot of new terminology. Knowing what the different terms mean is essential to understanding and describing the processes occurring in the cell.
Drag the terms on the left to correctly complete these sentences. Not all the terms will be used.
answer
sister chromatid(s)
centromere(s)
kinetocchore(s)
interphase
mitotic spindle (s)
chromatin
cytokinesis
centrosome (s)
question
The cell cycle represents the coordinated sequence of events in the life of a cell from its formation to its division into two daughter cells. Most of the key events of the cell cycle are restricted to a specific time within the cycle.
In this exercise, you will identify when various events occur during the cell cycle. Recall that interphase consists of the G1, S, and G2 subphases, and that the M phase consists of mitosis and cytokinesis.
Drag each label to the appropriate target.
answer
*Many organisms contain cells that do not normally divide. These cells exit the cell cycle before the G1 checkpoint.
Once a cell passes the G1 checkpoint, it usually completes the cell cycle--that is, it divides.
The first step in preparing for division is to replicate the cell's DNA in the S phase.
In the G2 phase, the centrosome replicates.
In early M phase, the centrosomes move away from each other toward the poles of the cell, in the process organizing the formation of the mitotic spindle.
At the end of the M phase when mitosis is complete, the cell divides (cytokinesis), forming two genetically identical daughter cells.
question
As the chromosomes of a parent cell are duplicated and distributed to the two daughter cells during cell division, the structure of the chromosomes changes.
Answer the three questions for each phase of the cell cycle by dragging the yes and no labels to the appropriate locations in the table.
Note: Assume that by the end of the M phase, the parent cell has not yet divided to form two daughter cells.
answer
Sister chromatids form when DNA replicates in the S phase. The sister chromatids become individual chromosomes once they separate in early anaphase.
Similarly, the cellular DNA content doubles in the S phase when the DNA replicates. However, the cell's DNA content does not return to its normal (undoubled) levels until after cytokinesis is complete and two daughter cells have formed.
The condensation state of the DNA is not related to the presence or absence of sister chromatids. The DNA condenses in prophase and remains condensed until after the sister chromatids separate and the new daughter cells begin to form. In late telophase/cytokinesis, the emphasis shifts to cell growth and DNA replication for the next cell cycle. For these processes to occur, the DNA needs to be de-condensed so it is accessible to the cellular machinery involved in transcription.
question
The stages of mitosis were originally defined by cellular features observable through a light microscope. The six micrographs below show animal cells (lung cells from a newt) during the five stages of mitosis, plus cytokinesis. (Note that interphase is not represented in these micrographs.) In these images, the chromosomes have been stained blue, microtubules green, and microfilaments red.
Drag each micrograph to the target that indicates the stage of mitosis or cytokinesis it shows.
answer
*As these six micrographs demonstrate, cellular events observable by light microscopy can be used to define the six stages of mitosis and cytokinesis. However, deciphering which stage is which in real cells can be much more challenging than in the drawings of idealized cells you see in your textbook. Thus, it is important to carefully observe the completeness of the mitotic spindle and the location of the chromosomes, as well as how condensed the chromosomes are.
question
Mitosis unfolds through a sequence of stages marked by specific events in the cell. The structural changes in the cell are brought about by a series of tightly coordinated underlying mechanisms.
Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. If a process occurs in more than one stage, sort it to the stage when it first occurs.
answer
*The micrographs in Part A show some of the cellular processes that occur during the stages of mitosis.
In prophase, the microtubules of the spindle apparatus begin to assemble from individual tubulin subunits. As the identical chromatids of each pair of sister chromatids condense during this stage, they are held together by cohesin proteins.
Prometaphase is marked by fragmentation of the nuclear envelope, expansion of the spindle into the nuclear region, and attachment of some spindle fibers to the chromosomes via the kinetochores.
Metaphase, marked by the alignment of chromsomes along the metaphase plate, is brought about by kinetochores aligning and then remaining motionless relative to the poles of the cell.
In anaphase, the cohesin proteins are cleaved, and the kinetochores move toward the poles of the cell, separating the sister chromatids.
As telophase proceeds, the kinetochore microtubules of the spindle disassemble. As the chromosomes reach the poles of the cell, the nuclear envelopes of the two new daughter nuclei form.
question
The mitotic spindle consists of two types of microtubules: kinetochore microtubules and nonkinetochore microtubules. In animal cells, these two types of microtubules function differently in the stages of mitosis.
Complete the sentences by dragging the labels to the appropriate locations. Labels may be used once, more than once, or not at all.
answer
lengthen
lengthen; shorten
disassemble
question
Consider three questions concerning the animal cell that has been treated with the inhibitor. Drag the labels to answer the questions. Labels may be used once, more than once, or not at all.
answer
y
y
n
question
In all cells, separation of replicated chromosomes is a prerequisite for cell division. However, the mechanism of chromosome separation in bacteria is distinct from that in eukaryotes in several ways.
Sort the following statements into the appropriate bin.
answer
bacteria only: chromosome separation begins at the origin of replication on the DNA.
Eukaryotes Only: two copies of the duplicated chromosome are attached at their centromes before separating.
Before separation, duplicated chromosomes condense.
nuclear envelope fragments permitting chromosome separation.
Both Bacteria and Eukaryotes: Replicated chromosomes separate by attaching to some other structural feature of the cell.
Chromosomes replicate before cell division.
question
Cytokinesis in animal cells is accomplished by constriction of the cell along the plane of cell division (formation of a cleavage furrow). In plant cells, which have cell walls, a completely different mechanism of cytokinesis has evolved.
Which of the following statements are true of cytokinesis in plant cells? Select the two that apply.
answer
The cell plate consists of the plasma membrane and cell wall that will eventually separate the two daughter cells.
Vesicles from the Golgi apparatus move along microtubules, coalesce at the plane of cell division, and form a cell plate.
question
Plant and animal cells also require cytoskeletal proteins for cytokinesis, although the roles these proteins play differ among bacteria, plants, and animals.
For each space in the table, drag the appropriate label to indicate if the statement is true or false for each group of organisms.
Which of these phases encompasses all of the stages of mitosis but no other events?
answer
E
question
During _____ both the contents of the nucleus and the cytoplasm are divided.
answer
the mitotic phase
question
During _____ the cell grows and replicates both its organelles and its chromosomes.
answer
interphase
question
Nucleoli are present during _____.
answer
interphase
question
Cytokinesis often, but not always, accompanies _____.
answer
telophase
question
Chromosomes become visible during _____.
answer
prophase
question
Centromeres divide and sister chromatids become full-fledged chromosomes during _____.
answer
anaphase
question
Spindle fibers attach to kinetochores during _____.
answer
prometaphase
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
anaphase
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
cytokinesis as it occurs in animal cells
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
prophase
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
metaphase
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
prometaphase
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
cytokinesis as it occurs in plant cells
question
Click on the art to see an animation. This animation illustrates the events of _____.
answer
telophase
question
During prophase a homologous pair of chromosomes consists of _____.
answer
two chromosomes and four chromatids
question
Which of the following is true of kinetochores?
answer
They are sites at which microtubules attach to chromosomes.
question
Which of the following correctly matches a phase of the cell cycle with its description?
answer
G1: follows cell division
question
In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this?
answer
large cells containing many nuclei
question
Which of the following is found in binary fission but not in mitosis?
answer
Duplicated chromosomes attach to the plasma membrane.
question
Cytochalasin B is a chemical that disrupts microfilament formation. How would this interfere with cell division?
answer
cleavage
question
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 _____.
answer
in the S phase of the cell cycle
question
The first gap in the cell cycle (G1) corresponds to _____.
answer
normal growth and cell function
question
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 _____.
answer
centrosome
question
In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit _____.
answer
the attachment of microtubules to kinetochores
question
The mitotic spindle is a microtubular structure that is involved in _____.
answer
separation of sister chromatids
question
Metaphase is characterized by _____.
answer
aligning of chromosomes on the equator
question
Kinetochore microtubules assist in the process of splitting centromeres by _____.
answer
creating tension by pulling toward opposite poles
question
Some cells have several nuclei per cell. How could such multinucleated cells be explained?
answer
The cell underwent repeated mitosis, but cytokinesis did not occur.
question
How is plant cell cytokinesis different from animal cell cytokinesis?
answer
Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
question
FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to _____.
answer
the cleavage furrow of eukaryotic animal cells
question
At which phase are centrioles beginning to move apart in animal cells?
answer
prophase
question
If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?
answer
10
question
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 _____.
answer
the structure of the mitotic spindle
question
Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?
answer
Golgi-derived vesicles
question
Movement of the chromosomes during anaphase would be most affected by a drug that prevents _____.
answer
shortening of microtubules
question
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?
answer
G2
question
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?
answer
16; 16
question
The beginning of anaphase is indicated by which of the following?
answer
Cohesin is cleaved enzymatically.
question
During which phase of mitosis do the chromatids become chromosomes?
answer
anaphase
question
A cleavage furrow is _____.
answer
a groove in the plasma membrane between daughter nuclei
question
What is the correct chromosomal condition at prometaphase of mitosis?
answer
B
question
What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?
answer
E
question
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?
answer
formation of telophase nuclei
question
In the figure above, G1 is represented by which numbered part(s) of the cycle?
answer
I or V
question
In the figure above, which number represents DNA synthesis?
answer
II
question
In the figure above, at which of the numbered regions would you expect to find cells at metaphase?
answer
III only
question
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
answer
gamma contains more DNA than beta
question
Several organisms, primarily protists, have what are called intermediate mitotic organization.
These protists are intermediate in what sense?
answer
They maintain a nuclear envelope during division.
question
What is the most probable hypothesis about these intermediate forms of cell division?
answer
They show some but not all of the evolutionary steps toward complete mitosis.
question
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 studentfaculty 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?
answer
What is the length of the S phase of the cell cycle?
question
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 _____.
answer
infection causes lymphocytes to divide more rapidly
question
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 _____.
answer
a plant cell in the process of cytokinesis
question
Which of the following does NOT occur during mitosis?
answer
replication of the DNA
question
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?
answer
cleavage furrow formation and cytokinesis
question
Motor proteins require which of the following to function in the movement of chromosomes toward the poles of the mitotic spindle?
answer
ATP as an energy source
question
Which of these is NOT a carcinogen?
answer
all of the above are carcinogens
question
_____ is a carcinogen that promotes colon cancer.
answer
fat
question
Which of the following is a function of the S phase in the cell cycle?
answer
The synthesis of sister chromatids
question
The copying of chromosomes occurs during which of the following phases of the cell cycle?
answer
S phase
question
For the first several divisions of early frog embryos, cells proceed directly from the M phase to the S phase and back to M without gaps. Which of the following is likely to be true about dividing cells in early frog embryos?
answer
The cells get smaller with each generation.
question
True or false? The M phase is characterized by the replication and division of a cell's chromosomes.
answer
F
question
If an organism normally has 34 chromosomes, how many molecules of DNA should there be in the G1 phase of the cell cycle?
answer
34
question
Which of the following events would cause the cell cycle to arrest?
answer
Poor nutrient conditions
question
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle?
answer
G1
question
Which of the following is true of benign tumors, but not malignant tumors?
answer
They remain confined to their original site
question
When cells were first taken from Henrietta Lacks, she was _____.
answer
suffering from cervical cancer
question
How did doctors harvest and culture cells from Henrietta Lacks?
answer
Cells were taken while she was being treated for cancer many years ago, and these cells have been cultured in the lab ever since.
question
Did doctors ask Henrietta Lacks' permission to take her cells, and was she paid for them?
answer
She was never told that her cells were being taken, and neither she nor her family has been compensated.
question
What property of Henrietta Lacks' cells was most unusual when they were grown in the laboratory?
answer
They continue to divide and multiply after decades of culture.
question
Cells taken from Henrietta Lacks have been used for experiments leading to _____.
answer
tests of the effects of atomic radiation on life
new treatments for cancer
the development of a polio vaccine
question
What treatment is being compared to the control in the experiment?
answer
The treated glioblastoma cells were cultured in the presence of an inhibitor from umbilical cord stem cells, but the control cells were cultured without the inhibitor.
question
The data are plotted in a type of graph called a histogram, which groups values for a numeric variable on the x-axis into intervals. A histogram allows you to see how an entire group of experimental subjects (cells, in this case) are distributed along a continuous variable (amount of fluorescence). In these histograms, the bars are so narrow that the data appear to follow a curve for which you can detect peaks and dips. Each bar represents the number of cells observed to have a fluorescence level in that interval. This in turn indicates the relative amount of DNA in those cells.
Which axis indirectly shows the relative amount of DNA per cell? By what relationship?
answer
The x-axis; the DNA was stained, so there is a positive correlation between fluorescence and DNA content.
question
Which region shows the population of cells with the highest amount of DNA per cell?
answer
region C
question
Identify which phase of the cell cycle is represented by each region. The regions represent the same cell cycle phases in both histograms.
answer
region A: G1
region B: S
region C: G2
question
In the control sample histogram, does the population of cells in the S phase show a distinct peak? Why or why not?
answer
No; the DNA content per cell changes as the S phase progresses, so the cells in S phase have a range of fluorescence levels.
question
In the treated sample histogram, which phase of the cell cycle has the greatest number of cells?
answer
the G1 phase
question
Which statement best describes the difference(s) in the distribution of cells in the treated sample compared to the control sample?
answer
The treated cells are mostly in the G1 phase (region A), but in the control sample, there are peaks of cells in both G1 and G2 (region C).
question
What does the difference in distribution tell you about the cells in the treated sample?
answer
The treated cancer cells are arrested at the G1 phase.
question
Which mechanism is the best explanation for how the stem cell-derived inhibitor might arrest the cancer cell cycle at the G1 stage?
answer
The inhibitor might block the activity of a cyclin or signaling molecule of the G1 checkpoint.
question
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 _____.
answer
are in the G0 phase.
question
Neurons and some other specialized cells divide infrequently because they _____.
answer
have entered into G0
question
MPF is a dimer consisting of _____.
answer
cyclin and a cyclin-dependent kinase
question
Cyclin-dependent kinase (Cdk) is _____.
answer
an enzyme that attaches phosphate groups to other proteins
question
What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2?
answer
The cells enter mitosis.
question
Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis?
answer
The cyclin component of MPF is degraded.
question
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 _____.
answer
metaphase
question
Which of the following is released by platelets in the vicinity of an injury?
answer
PDGF
question
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?
answer
cyclin
question
Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?
answer
MPF
question
The cyclin component of MPF is destroyed toward the end of which phase?
answer
M
question
In the figure above, MPF reaches its highest concentration during this stage.
answer
III
question
Density-dependent inhibition is explained by which of the following?
answer
As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.
question
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
answer
lack of appropriate cell death
question
Anchorage dependence of animal cells in vitro or in vivo depends on which of the following?
answer
response of the cell cycle controls to signals from the plasma membrane
question
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?
answer
The cells show characteristics of tumors.
question
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
answer
It interferes with rapidly dividing cells.
question
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?
answer
Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
question
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?
answer
They are involved in the disassembly of the nuclear envelope.
question
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.
Select the statement that makes a correct prediction about natural phenomena that could occur during the cell cycle to prevent cell growth.
answer
As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.
question
The person credited with first recognizing (in the 1860s) that living cells cannot arise spontaneously, but arise only from previously existing cells, is __________.
answer
Rudolf Virchow
question
What is the difference between a benign tumor and a malignant tumor?
answer
Cells of benign tumors do not metastasize; those of malignant tumors do.
question
The function of the mitotic cell cycle is to produce daughter cells that __________.
answer
are genetically identical to the parent cell (assuming no mutation has occurred)
question
Which of the following hypotheses is best supported by observing cancer cells in a culture?()
answer
The cancer cells do not exhibit density-dependent inhibition.
question
You would be UNLIKELY to see which of the following human cells dividing?
answer
nerve cell
question
Can you match the terms associated with cancer to their descriptions?
answer
benign tumor
malignant tumor
Metastasis
cancer
carcinoma
question
In sexually reproducing multicellular organisms, the main functions of mitosis are _____.
answer
growth and development
tissue repair/replacement of damaged cells
question
Which events occur during prophase?
answer
The nuclear envelope breaks down.
Chromosomes condense and are attached to spindle fibers.
question
Cytokinesis _____.
answer
finishes mitosis by dividing the cytoplasm and organelles of the original parent cell into two separate daughter cells
question
During _____, the cell carries out its normal functions and the chromosomes are thinly spread out throughout the nucleus.
answer
interphase
question
Looking through a light microscope at a dividing cell, you see two separate groups of chromosomes on opposite ends of the cell. New nuclear envelopes are taking shape around each group. The chromosomes then begin to disappear as they unwind. You are witnessing _____.
answer
telophase
question
During binary fission in a bacterium, __________.
answer
the origins of replication move apart
question
A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled __________.
answer
between the G1 and G2 phases
question
What must happen before a cell can begin mitosis?
answer
The chromosomes must be duplicated.
question
The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
answer
Prophase
question
The chromosomes line up in the center of the cell during which phase of mitosis?
answer
Metaphase
question
The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
answer
Anaphase
question
The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
answer
Telophase
question
At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.
answer
cytokinesis
question
Which of the following is FALSE regarding sister chromatids?
answer
Both of the sister chromatids end up in the same daughter cell after cytokinesis has occurred.
question
The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.
answer
chromatin
question
Which of the following is involved in the binary fission of most bacteria?
answer
distribution of a copy of the single parental chromosome to each daughter cell
question
The region of a chromosome in which the two double strands of replicated DNA are held together is called __________.
answer
a centromere
question
Which of the following processes does NOT occur in dividing bacteria?
answer
mitosis
question
The centromere is a region in which __________.
answer
sister chromatids are attached to one another in prophase
question
A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in one of the grasshopper daughter cells?
answer
100 units
question
How many maternal chromosomes are present in a somatic human cell not engaged in cell division?
answer
23
question
Which of the following does NOT occur during mitosis?
answer
replication of chromosomes
question
Tissue culture experiments with PDGF demonstrate that without this substance __________.
answer
fibroblasts fail to divide
question
A cell entering the cell cycle with 32 chromosomes will produce two daughter cells, each with __________.
answer
none of the listed numbers of chromosomes
question
Chromatids are __________.
answer
identical copies of each other if they are part of the same duplicated chromosome
question
During interphase, the genetic material of a typical eukaryotic cell is __________.
answer
dispersed in the nucleus as long strands of chromatin
question
In telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in __________.
answer
prophase
question
"Cytokinesis" refers to __________.
answer
the division of the cytoplasm
question
If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell at the completion of the cell cycle?
answer
30
question
DNA replication occurs in __________.
answer
the S phase of interphase
question
Which of the following phases of mitosis is essentially the OPPOSITE of prometaphase in terms of the nuclear envelope?
answer
telophase
question
In animal cell mitosis, the cleavage furrow forms during which stage of the cell cycle?
answer
cytokinesis
question
If a human somatic cell is just about to divide, it has __________ chromatids.
answer
92
question
Are sister chrmatids present in all or part of this phase?
answer
G1: no.
S: yes
G2: yes
Beginning of M (pro-early ana): yes
End of M ( late ana-telo): no
question
Is the DNA condense in all or part of this phase?
answer
G1: no
S: no
G2: no
Beginning of M (pro-early ana): yes
End of M ( late ana-telo): es
question
Does the cell contain twice as much DNA in this phase as it did in the G1 Phase?
answer
G1: no.
S: yes
G2: yes
Beginning of M (pro-early ana): yes
End of M ( late ana-telo): yes
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