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

Once a cell enters mitosis, the molecules that activate division must be turned off. What happens to MPF during mitosis?

The cyclin component of MPF is degraded.

What would you expect to happen if MPF (maturation-promoting factor) is introduced into immature frog oocytes that are arrested in G2?

The cells would enter mitosis.

Which of the following properties is associated with a cyclin-dependent kinase (Cdk)?

A Cdk is an enzyme that attaches phosphate groups to other proteins.

What two components constitute an active MPF?

cyclin and a cyclin-dependent kinase

Why do neurons and some other specialized cells divide infrequently?

They have entered into G0.

Use the data in the accompanying table to answer the question.

Minutes Spent in Cell Cycle Phases

The data in the table 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. What is the best explanation for the data associated with delta cells?

Delta cells are in the G0 phase.

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

ATP as an energy source

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?

cleavage furrow formation and cytokinesis

Which of the following events occurs during interphase of the cell cycle?

replication of the DNA

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

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 to study the incorporation of labeled nucleotides into a culture of lymphocytes. They found that the lymphocytes incorporated the labeled nucleotide at a significantly higher level after a pathogen was introduced into the culture. What might they conclude from this observation?

Infection causes lymphocytes to divide more rapidly.

Nucleotides can be radiolabeled before they are incorporated into newly synthesized 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 a culture of dividing human cells at specific times. Which of the following questions might be answered by using the method described?

What is the length of the S phase of the cell cycle?

Several organisms, primarily protists, have what are called intermediate mitotic organization. What is the most probable hypothesis about these intermediate forms of cell division?

They show some but not all of the evolutionary steps toward complete mitosis.

Certain unicellular eukaryotes, including diatoms and some yeasts, have mechanisms of nuclear division that may resemble intermediate steps in the evolution of mitosis. Which of the following is a characteristic feature of nuclear division in these organisms?

Chromosomes are segregated by a mitotic spindle, but the nuclear envelope remains intact during division.

Use the data in the accompanying table to answer the question.

Minutes Spent in Cell Cycle Phases

The data in the table 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.

Which of the statements is the best explanation for the difference between time spent in S phase by beta and gamma?

Gamma contains more DNA than beta.

Use the figure to answer the question below.

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

III only

Use the figure to answer the question below.

In the figure, which number represents DNA synthesis?

II

Use the figure to answer the question below.

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

I and V

Use the figure to answer the question below.

If the cell whose nuclear material is shown in the figure continues toward completion of mitosis, which of the following events would occur next?

formation of telophase nuclei

Use the figure to answer the question below.

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

Use the figure to answer the question below.

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

A cleavage furrow is ________.

a groove in the plasma membrane between daughter nuclei

During which phase of mitosis do the chromatids become chromosomes?

anaphase

The beginning of anaphase is indicated by which of the following processes?

Enzymatic cleavage of cohesin.

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 of DNA would be found in a nucleus at prophase of mitosis?

16

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

Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following events in mitosis and cell division?

shortening of microtubules

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerization. Thus, Taxol stops mitosis by interfering with which of the following structures or processes?

the mitotic spindle

If a cell at metaphase of mitosis contains 20 sister chromatids, how many chromosomes will be present in a G1 cell?

10

If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis?

20

In a diploid cell with 5 chromosome pairs (2n = 10), how many sister chromatids will be found in a nucleus at prophase of mitosis?

20

At which phase of the cell cycle do centrioles begin to move apart in animal cells?

prophase

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in binary fission. Its function is analogous to ________.

the cleavage furrow of eukaryotic animal cells

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.

Certain cell types normally have several nuclei per cell. How could such multinucleated cells be explained?

The cell underwent repeated mitosis, but cytokinesis did not occur.

In what way do kinetochore microtubules facilitate the process of splitting the centromeres?

They create tension by pulling toward opposite poles.

Metaphase is characterized by ________.

alignment of chromosomes on the equator of the cell

The mitotic spindle plays a critical role in which of the following processes?

separation of sister chromatids

In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle?

attachment of microtubules to kinetochores

What is the name of the microtubule-organizing center found in animal cells as an identifiable structure present during all phases of the cell cycle?

centrosome

G1 is associated with which of the following cellular events?

normal growth and cell function

Scientists isolate cells in various phases of the cell cycle. They isolate a group of cells that have 1 1/2 times more DNA than G1 phase cells. What is the most likely part of the cell cycle from which these cells were isolated?

in the S phase of the cell cycle

In a diploid cell with 5 chromosome pairs (2n = 10), how many centromeres will be found in a nucleus at G2 of the cell division cycle?

10

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

64

Eukaryotic chromosomes are composed of which of the following macromolecules?

DNA and proteins