Chapter 12- Mitosis and Cell Cycle

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. 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

If there are 20 chromatids in a cell, how many centromeres are there?

20

Th MPF protein complex turns itself off by

Activating a process that destroys cyclin components

What is the correct chromosomal condition at pro-metaphase of mitosis

B

Kinetochore microtubules assist in the process of distributing chromosomes to daughter cells by ____

Creating tension by pulling toward opposite poles

In eukaryotic cells, chromosomes are composed of

DNA and proteins

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 grey. The circles labelled A to E show various combos of these chromosomes. Which is the correct chromosomal condition for one daughter nucleus at telophase of mitosis?

E

Tumor Supressing Genes

Encode proteins that help prevent uncontrolled cell growth

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. 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 3-6 picograms per nucleus . In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

G2

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

Golgi-derived vesicles

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

I or V

In the figure, which number represents DNA synthesis?

II

In the figure, which number represents the point in the cell cycle during which the chromosomes are replicated?

II

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

III

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

III only

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

IV

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. 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 M-Phase checkpoint endure that all chromosomes are attached to the mitotic spindle. If this does NOT happen, cells would most likely be arrested in ___

Metaphase

The data were obtained from a study in a length of time spent in each phase of the cell cycle by cells of three eukaryotic organisms designated beta, gamma, and delta The first gap in the cell cycle (G1) correspond to

Normal growth and cell function

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.

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

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

What happens if MPF is introduced into immature frog oocytes that are arrested innG2

The cells enter mitosis

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.

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.

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 structure of the mitotic spindle

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.

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 using the method described?

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

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 cytoskeletal proteins are important constituents of the contractile structures that form the cleavage furrows involved in animal cell cytokinesis?

actin

A cyclin

activates a Cdk molecule when it is in sufficient concentration

Cyclin-dependent kinase (Cdk) is

an enzyme that attaches phosphate groups to other proteins

During which phase of mitosis do the chromatids become chromosomes?

anaphase

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

are in the G0 phase.

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in

cells with more than one nucleus

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

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

Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called

cyclins

Mitosis separates chromosomes. Cytoplasm is divided between two daughter cells by _____.

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.

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

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

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

have entered into G0

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

The product of the p53 gene

inhibits the cell cycle

A cell in late anaphase of mitosis will have ________.

no chromosomes in the center of the cell

If a cell has accumulated DNA damage, it is unlikely to _____.

pass the G2 checkpoint

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

prophase

Which of the following does NOT occur during mitosis

replication of DNA

The mitotic spindle is a micro tubular structure that is involved in

separation of sister chromatids

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

shortening of microtubules

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

the attachment of microtubules to kinetochores

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

The decline of MPF activity at the end of mitosis is due to

the degradation of cyclin.

Regulatory proteins that prevent a cell from entering the S phase under conditions of DNA damage are also known as

tumor suppressors