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

32

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

10

Which of the following is a true statement about sexual vs. asexual reproduction?

In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring

In eukaryotic cells, chromosomes are composed of _____.

DNA and proteins

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

cytokinesis

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

The cell underwent repeated mitosis, but cytokinesis did not occur

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

actin

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

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

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

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

prophase

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 _____.

the structure of the mitotic spindle

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

Golgi-derived vesicles

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

shortening of microtubules

During which phase of mitosis do the chromatids become chromosomes?

anaphase

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

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

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?

formation of telophase 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

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

In the cells of some organisms, mitosis occurs without cytokinesis. This results in _____

cells with more than one nucleus

Which of the following does NOT occur during mitosis

replication of the DNA

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

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

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

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

the attachment of microtubules to kinetochores

The mitotic spindle is a microtubular structure that is involved in _____.

separation of sister chromatids

Kinetochore microtubules assist in the process of splitting centromeres by _____

creating tension by pulling toward opposite poles

The product of the p53 gene _____.

inhibits the cell cycle

Researchers pulsed rapidly dividing cultured cells with radioactive thymidinefor 30 minutes. The cells were then exposed to a solution containing non-radiolabeled thymidine. Cells were analyzed at 2-hour intervals. At the 2-hour time point, no cells appeared to be dividing. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way:

There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division

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

normal growth and cell function

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

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

A cell in late anaphase of mitosis will have _____

no chromosomes in the center of the cell

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

The cells enter mitosis.

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.

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

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

pass the G₂ checkpoint

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

tumor suppressors

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

cyclins

The MPF protein complex turns itself off by _____

activating a process that destroys cyclin components

Cyclin-dependent kinase (Cdk) is _____

an enzyme that attaches phosphate groups to other proteins

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

have entered into G₀

A cyclin _____

activates a Cdk molecule when it is in sufficient concentration

The following question are based on the accompanying figure.

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

IV

The following question are based on the accompanying figure.

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

I or V

In the figure above, which number represents DNA synthesis?

II

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

II

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

III only

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

III

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 _____.

gamma contains more DNA than beta

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 _____

are in the G₀ phase.

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 question might be answered by using the method described?

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

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 _____.

infection causes lymphocytes to divide more rapidly

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

the degradation of cyclin

Tumor-suppressor genes _____.

encode proteins that help prevent uncontrolled cell growth

BRCA1 and BRCA2 are considered to be tumor-suppressor genes because _____.

their normal products participate in repair of DNA damage

The cancer-causing forms of the Ras protein are involved in which of the following processes

relaying a signal from a growth factor receptor

Forms of the Ras protein found in tumors usually cause which of the following?

excessive cell division