Use the data in the accompanying table to answer the following questions. 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. The best conclusion concerning delta is that the cells _____.

1. are in the G0 phase.
2. contain no RNA.
3. contain no DNA.
4. divide in the G1 phase.

a

Which of the following triggers the cell's passage past the G2 checkpoint into mitosis?

1. MPF
2. cyclin
3. PDGF
4. Cdk

a

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?

1. M
2. G2
3. G1
4. S

b

In the figure above, which number represents DNA synthesis?

1. I
2. II
3. III
4. IV

b

Metaphase is characterized by _____.

1. splitting of the centromeres
2. separation of sister chromatids
3. aligning of chromosomes on the equator
4. cytokinesis

c

Some cells have several nuclei per cell. How could such multinucleated cells be explained?

1. The cell underwent repeated mitosis with simultaneous cytokinesis.
2. The cell underwent repeated mitosis, but cytokinesis did not occur.
3. The cell underwent repeated cytokinesis but no mitosis.
4. The cell had multiple S phases before it entered mitosis.

b

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?

1. 16; 16
2. 16; 8
3. 8; 8
4. 8; 16

a

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells?

1. kinetochores
2. centrioles and centromeres
3. Golgi-derived vesicles
4. actin and myosin

c

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.

1. As cells become more numerous, the protein kinases they produce begin to compete with each other until only one cell has the proteins necessary for growth.
2. As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to allow cell growth.
3. As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.
4. As cells become more numerous, more and more of them enter the synthesis part of the cell cycle and duplicate DNA to inhibit cell growth.

c

Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have times more DNA than G1 phase cells. The cells of this group are _____.

1. in the G2 phase of the cell cycle
2. in the M phase of the cell cycle
3. in the S phase of the cell cycle
4. between the G1 and S phases in the cell cycle

c

Which of the following does NOT occur during mitosis?

1. separation of the spindle poles
2. spindle formation
3. replication of the DNA
4. condensation of the chromosomes

c

Use the following information to answer the questions below. 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 questions might be answered by using the method described?

1. What is the length of the S phase of the cell cycle?
2. How many picograms of DNA are made per cell cycle?
3. When do spindle fibers attach to chromosomes?
4. How many cells are produced by the culture per hour?

a

The cyclin component of MPF is destroyed toward the end of which phase?

1. G2
2. G1
3. M
4. S

c

Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor?

1. changes in the order of cell cycle stages
2. inability of chromosomes to meet at the metaphase plate
3. inability to form spindles
4. lack of appropriate cell death

d

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 _____.

1. centrosome
2. centromere
3. kinetochore
4. microtubulere

a

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable?

1. It interferes with rapidly dividing cells.
2. It does not alter metabolically active cells.
3. It is safe enough to limit all apoptosis.
4. It interferes with cells entering G0.

a

In the figure above, at which of the numbered regions would you expect to find cells at metaphase?

1. I and IV
2. II only
3. III only
4. IV only

c

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?

1. 80
2. 40
3. 20
4. 10

d

Density-dependent inhibition is explained by which of the following?

1. As cells become more numerous, the level of waste products increases, eventually slowing down metabolism.
2. As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to produce control factors.
3. As cells become more numerous, the protein kinases they produce begin to compete with each other, such that the proteins produced by one cell essentially cancel those produced by its neighbor.
4. As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing.

c

Which of the following is released by platelets in the vicinity of an injury?

1. cyclin
2. PDGF
3. MPF
4. Cdk

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?

1. B
2. C
3. D
4. E

d

Movement of the chromosomes during anaphase would be most affected by a drug that prevents _____.

1. shortening of microtubules
2. formation of a cleavage furrow
3. nuclear envelope breakdown
4. elongation of microtubules

a

Neurons and some other specialized cells divide infrequently because they _____.

1. show a drop in MPF concentration
2. can no longer bind Cdk to cyclin
3. no longer have active nuclei
4. have entered into G0

d

Metaphase is characterized by _____.

1. splitting of the centromeres
2. separation of sister chromatids
3. aligning of chromosomes on the equator
4. cytokinesis

c

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 _____.

1. infection causes cell cultures in general to reproduce more rapidly
2. the presence of the pathogen made the experiments too contaminated to trust the results
3. infection causes lymphocytes to divide more rapidly
4. infection causes lymphocyte cultures to skip some parts of the cell cycle

c

The cyclin component of MPF is destroyed toward the end of which phase?

1. G2
2. G1
3. M

S

c

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?

1. B
2. C
3. D
4. E

a

Anchorage dependence of animal cells in vitro or in vivo depends on which of the following?

1. response of the cell cycle controls to signals from the plasma membrane
2. attachment of spindle fibers to centrioles
3. response of the cell cycle controls to the binding of cell-surface phospholipids
4. the binding of cell-surface phospholipids to those of adjoining cells

a

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?

1. The cells are unable to form spindle microtubules.
2. The cells show characteristics of tumors.
3. They were originally derived from an elderly organism.
4. They have altered the series of cell cycle phases.

b

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 _____.

1. telophase
2. prometaphase
3. metaphase
4. prophase

c

Several organisms, primarily protists, have what are called intermediate mitotic organization. These protists are intermediate in what sense?

1. They use mitotic division but only have circular chromosomes.
2. None of them form spindles.
3. They reproduce by binary fission in their early stages of development and by mitosis when they are mature.
4. They maintain a nuclear envelope during division.

d

In the figure above, G1 is represented by which numbered part(s) of the cycle?

1. I or V
2. II or IV
3. III only
4. V only

a

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?

1. Cdk
2. cyclin
3. PDGF
4. MPF

b

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?

1. Cancer cells are no longer density-dependent.
2. Transformation introduces new chromosomes into cells.
3. Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
4. Cancer cells are no longer anchorage-dependent.

c

What is the final result of mitosis in a human?

1. genetically identical 2n somatic cells
2. genetically identical 1n somatic cells
3. genetically different 2n somatic cells
4. genetically identical 2n gamete cells

a

In eukaryotic cells, chromosomes are composed of _____.

1. DNA and phospholipids
2. DNA and RNA
3. DNA only
4. DNA and proteins

d

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 _____.

1. infection causes cell cultures in general to reproduce more rapidly \
2. the presence of the pathogen made the experiments too contaminated to trust the results
3. infection causes lymphocytes to divide more rapidly
4. infection causes lymphocyte cultures to skip some parts of the cell cycle

c

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

1. 32
2. 16
3. 8
4. 64

a

What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2?

1. Cell differentiation is triggered.
2. The cells undergo meiosis.
3. The cells enter mitosis.
4. Nothing happens.

c

In the figure above, MPF reaches its highest concentration during this stage.

1. I
2. II
3. III
4. IV

c

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 _____.

1. anaphase
2. formation of the centrioles
3. chromatid assembly
4. the structure of the mitotic spindle

d

In human and many other eukaryotic species' cells, the nuclear membrane has to disappear to permit _____.

1. the disassembly of the nucleolus
2. the splitting of the centrosomes
3. cytokinesis
4. the attachment of microtubules to kinetochores

d

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 _____.

1. an animal cell in the process of cytokinesis
2. a plant cell in metaphase
3. a plant cell in the process of cytokinesis
4. an animal cell in the S phase of the cell cycle

c

What is the correct chromosomal condition at prometaphase of mitosis?

1. B
2. C
3. D
4. E

a

Cyclin-dependent kinase (Cdk) is _____.

1. an enzyme that attaches phosphate groups to other proteins
2. the enzyme that catalyzes the attachment of chromosomes to microtubules
3. inactive, or "turned off," in the presence of cyclin
4. present only during the S phase of the cell cycle

a

Which of the following questions might be answered by using the method described?

1. What is the length of the S phase of the cell cycle?
2. How many picograms of DNA are made per cell cycle?
3. When do spindle fibers attach to chromosomes?
4. How many cells are produced by the culture per hour?

a

The first gap in the cell cycle (G1) corresponds to _____.

1. the phase in which DNA is being replicated
2. the beginning of mitosis
3. normal growth and cell function
4. the phase between DNA replication and the M phase

c

How is plant cell cytokinesis different from animal cell cytokinesis?

1. The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells.
2. Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase.
3. Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
4. The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile phospholipids.

c

At which phase are centrioles beginning to move apart in animal cells?

1. anaphase
2. metaphase
3. prophase
4. prometaphase

c

Kinetochore microtubules assist in the process of splitting centromeres by _____

1. phosphorylating the centromere, thereby changing its conformation
2. sliding past each other like actin filaments
3. using motor proteins to split the centromere at specific arginine residues
4. creating tension by pulling toward opposite poles

d

Of the following, the best conclusion concerning the difference between the S phases for beta and gamma is that _____.

1. beta cells reproduce asexually
2. beta is a plant cell and gamma is an animal cell
3. beta and gamma contain the same amount of DNA
4. gamma contains more DNA than beta

d

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?

1. cell elongation during anaphase
2. spindle attachment to kinetochores
3. cleavage furrow formation and cytokinesis
4. spindle formation

c

Motor proteins require which of the following to function in the movement of chromosomes toward the poles of the mitotic spindle?

1. a microtubule-organizing center
2. intact centromeres
3. ATP as an energy source
4. synthesis of cohesin

c