Chapter 12 + 13 AP Biology
The centromere is a region in which
chromatids remain attached to one another until anaphase.
Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active?
Cdk
Which of the following describe(s) cyclin-dependent kinase (Cdk)?
Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins. Answer: E
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
Movement 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
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
Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?
32
A triploid cell contains three sets of chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following?
63 chromosomes in 21 sets of 3
Which of the following is an example of alternation of generations?
A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
In the human species, all somatic cells have 46 chromosomes. Which of the following can also be true?
A plant species (privet shrubs) has 46 chromosomes per cell.
Which of the following is (are) required for motor proteins to function in the movement of chromosomes toward the poles of the mitotic spindle?
ATP as an energy source
Density-dependent inhibition is explained by which of the following?
As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.
Which of these statements is false?
At sexual maturity, ovaries and testes produce diploid gametes by meiosis.
The lettered circle in Figure 12.1 shows a diploid nucleus with four chromosomes. There are two pairs of homologous chromosomes, one long and the other short. One haploid set is symbolized as black and the other haploid set is gray. The chromosomes in the unlettered circle have not yet replicated. Choose the correct chromosomal conditions for the following stages. What is the correct chromosomal condition at the prometaphase of mitosis?
B
For a newly evolving protist, what would be the advantage of using eukaryote-like cell division rather than binary fission?
Cell division would allow for the orderly and efficient segregation of multiple linear chromosomes.
Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?
Chromosomally abnormal cells can still go through cell cycle checkpoints.
If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants?
Clone the plant asexually to produce an identical one.
For anaphase to begin, which of the following must occur?
Cohesin must be cleaved enzymatically.
What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?
E
Which of the following is true of a species that has a chromosome number of 2n = 16?
Each cell has eight homologous pairs.
The somatic cells of a privet shrub each contain 46 chromosomes. To be as different as they are from human cells, which have the same number of chromosomes, which of the following must be true?
Genes of privet chromosomes are significantly different than those in humans.
Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?
Golgi-derived vesicles
After which checkpoint is the cell first committed to continue the cell cycle through M?
G₁
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.
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
Which number represents DNA synthesis?
II
Which number represents the point in the cell cycle during which the chromosomes are replicated?
II
G₁ is represented by which numbered part(s) of the cycle?
I or V
Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do all sexual life cycles have in common? I. Alternation of generations II. Meiosis III. Fertilization IV. Gametes V. Spores
II, III, and IV
MPF reaches its threshold concentration at the end of this stage.
III
At which of the numbered regions would you expect to find cells at metaphase?
III only
In the figure above, mitosis is represented by which numbered part(s) of the cycle?
IV
Which of the following is a true statement about sexual vs. asexual reproduction?
In sexual reproduction, individuals transmit 50% of their genes to each of their offspring.
Which of the following most accurately describes a cyclin?
It activates a Cdk molecule when it is in sufficient concentration.
If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following is an appropriate description of its contents?
It has half the amount of DNA as the cell that began meiosis.
For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?
It interferes with rapidly dividing cells.
A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?
Its gametes must have 23 chromosomes.
You have a series of cells, all of which were derived from tumors, and you first need to find out which ones are malignant. What could you do?
Karyotype samples to look for unusual size and number of chromosomes.
The cyclin component of MPF is destroyed toward the end of which phase?
M
Which of the following triggers the cell's passage past the G₂ checkpoint into mitosis?
MPF
Which of the following is released by platelets in the vicinity of an injury?
PDGF
At the M phase checkpoint, the complex allows for what to occur?
Separase enzyme cleaves cohesins and allows chromatids to separate.
A particular cyclin called cyclin E forms a complex with Cdk 2 (cyclin-dependent kinase 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 of free cyclin E is highest 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.
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?
The cells show characteristics of tumors.
Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?
The chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules.
A plant-derived protein known as colchicine can be used to poison cells by blocking the formation of the spindle. Which of the following would result if colchicine is added to a sample of cells in G₂?
The chromosomes would coil and shorten but have no spindle to which to attach.
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 female 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 the research team's conclusions?
The elderly persons' samples demonstrated their lowered immune responses.
All cell cycle checkpoints are similar in which way?
They activate or inactivate other proteins.
Why do neurons and some other specialized cells divide infrequently?
They have been shunted into G₀.
Several organisms, primarily protists, have what are called intermediate mitotic organization. These protists are intermediate in what sense?
They maintain a nuclear envelope during division.
Several organisms, primarily protists, have what are called intermediate mitotic organization.
They show some but not all of the evolutionary steps toward complete mitosis.
Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can therefore 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 questions might be answered by such a method?
What is the length of the S phase of the cell cycle?
Which of the following is true concerning cancer cells?
When they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.
A student is looking through his light microscope (~450 X) at a squashed and stained onion root tip. Some, but not all, of the cells have clearly visible chromosome strands. When a cell is in anaphase of mitosis, which of the following will he see?
a clear area in the center of the cell
Which of the following best describes a karyotype?
a display of each of the chromosomes of a single cell
What is a cleavage furrow?
a groove in the plasma membrane between daughter 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.
Which of the following can utilize both mitosis and meiosis in the correct circumstances?
a plantlike protist
Which of the following proteins are involved in binary fission as well as eukaryotic mitotic division?
actin and tubulin
The MPF protein complex turns itself off by
activating a process that destroys cyclin components.
Which of the following might result in a human zygote with 45 chromosomes?
an error in either egg or sperm meiotic anaphase
The best conclusion concerning delta is that the cells
are actually in the G₀ phase.
In the cells of some organisms, mitosis occurs without cytokinesis. This will result in
cells with more than one nucleus.
Where do the microtubules of the spindle originate during mitosis in both plant and animal cells?
centrosome
One difference between cancer cells and normal cells is that cancer cells
continue to divide even when they are tightly packed together.
Once they had determined which cells were dividing, the team wanted to use a non-radioactive method to track whether various physiological factors (such as food or body temperature) affect the action of the pathogen. Which of the following would be effective, simple, and safe?
counting the frequency of cells in mitosis
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?
cyclin
Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called
cyclins.
In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?
dinoflagellates and diatoms only
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.
The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following?
either anaphase I or II
The human genome is minimally contained in which of the following?
every human cell
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?
formation of telophase nuclei
Referring to a plant's sexual life cycle, which of the following terms describes the process that leads directly to the formation of gametes?
gametophyte mitosis
Use the data in Table 12.1 to answer the following question. (SEE IMAGE) 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 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.
Which of the following was a discovery that had to be made before human chromosomes could be correctly counted?
how to use a hypotonic solution to swell nuclei
The human X and Y chromosomes
include genes that determine an individual's sex.
Nucleotides can be radiolabeled before they are incorporated into newly forming DNA and can therefore 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 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
infection causes lymphocytes to divide more rapidly.
What causes the decrease in the amount of cyclin at a specific point in the cell cycle?
its destruction by a process initiated by the activity of its complex with a cyclin
Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?
lack of appropriate cell death
Which of the following is a function of those spindle microtubules that do not attach to kinetochores?
maintaining the region of overlap of microtubules in the cell's center
At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?
metaphase
If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested?
metaphase
You have the technology necessary to measure each of the following in a sample of animal cells: chlorophylls, organelle density, picograms of DNA, cell wall components, and enzymatic activity. Which would you expect to increase significantly from M to G₁?
organelle density and enzymatic activity
At which phase are centrioles beginning to move apart in animal cells?
prophase
Using which of the following techniques would enable your lab group to distinguish between a cell in G₂ and a cell from the same organism in G₁?
radioactive-labeled nucleotides
Which of the following does not occur during mitosis?
replication of the DNA
What explains anchorage dependence of animal cells in vitro or in vivo?
response of the plasma membrane to cell cycle controls
During which phase of mitosis do the chromatids become chromosomes?
telophase
Which of the following investigations might be most productive to show what the data on the teenagers might indicate?
test female teens at different times in their menstrual cycles
Which of the following defines a genome?
the complete set of an organism's genes
The decline of MPF activity at the end of mitosis is due to
the degradation of cyclin.
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
the formation of the mitotic spindle.
A karyotype results from which of the following?
the ordering of human chromosome images
Why do chromosomes coil during mitosis?
to allow the chromosomes to move without becoming entangled and breaking
Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal) nucleus. It might consist of which of the following?
two long strands of DNA plus proteins
When the cell has just completed telophase, which of the following does he see?
two small cells with chromatin