Chapter 12: Quiz

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? A) 10 B) 5 C) 40 D) 20

A) 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 of DNA would be found in a nucleus at prophase of mitosis? A) 16 B) 4 C) 8 D) 24

A) 16

If there are 40 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis? A) 20 B) 40 C) 10 D) 80

A) 20

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? A) B B) C C) D D) E

A) B

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? A) Infection causes lymphocytes to divide more rapidly. B) Infection causes lymphocyte cultures to skip some parts of the cell cycle. C) The pathogen consumed radiolabeled nucleotides. D) Infection causes lymphocytes to increase in size.

A) Infection causes lymphocytes to divide more rapidly.

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) a plant cell in the process of cytokinesis B) an animal cell in anaphase of mitosis C) an animal cell in the process of cytokinesis D) a plant cell in metaphase of mitosis

A) a plant cell in the process of cytokinesis

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in A) cells with more than one nucleus. B) cells lacking nuclei. C) cell cycles lacking an S phase. D) cells that are unusually small.

A) cells with more than one nucleus.

Which of the following molecules is a protein synthesized at specific times during the cell cycle that associates with a kinase to form a catalytically active complex? A) cyclin B) PDGF C) MPF D) Cdk

A) cyclin

What is the final result of mitosis in a human? A) genetically identical 2n somatic cells B) genetically different 2n somatic cells C) genetically identical 1n somatic cells D) genetically identical 2n gamete cells

A) genetically identical 2n somatic cells

At what stage of the cell cycle is the cyclin component of MPF destroyed? A) in late M B) in early G2 C) in late G1 D) at mid-S phase

A) in late M

Which of the following events occurs during interphase of the cell cycle? A) replication of the DNA B) condensation of the chromosomes C) spindle formation D) separation of the spindle poles

A) replication of the DNA

The mitotic spindle plays a critical role in which of the following processes? A) separation of sister chromatids B) dissolving the nuclear membrane C) triggering the compaction and condensation of chromosomes D) splitting of the cell (cytokinesis) following mitosis

A) separation of sister chromatids

The decline of MPF activity at the end of mitosis is due to A) the degradation of cyclin. B) decreased synthesis of Cdk. C) the accumulation of cyclin. D)the destruction of the protein kinase Cdk.

A) the degradation of cyclin.

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? A) the mitotic spindle B) centriole duplication C) chromosome condensation D) cytokinesis

A) the mitotic spindle

In a diploid cell with 5 chromosome pairs (2n = 10), how many sister chromatids will be found in a nucleus at prophase of mitosis? A) 40 B) 20 C) 10 D) 5

B) 20

Which of the following properties is associated with a cyclin-dependent kinase (Cdk)? A) A Cdk is an enzyme that catalyzes the attachment of kinetochores to microtubules. B) A Cdk is an enzyme that attaches phosphate groups to other proteins. C) The number of Cdk molecules increases during the S and G2phases and decrease during M. D) A Cdk is inactive, or "turned off," in the presence of a cyclin.

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

Density-dependent inhibition is explained by which of the following processes? A) As cells become more numerous, the level of waste products increases, which slows metabolism and inhibits growth. B) As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing. C) As cells become more numerous, they begin to squeeze against each other, restricting their size. D) 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.

B) As cells become more numerous, the cell surface proteins of one cell contact the adjoining cells, and they signal each other to stop dividing.

Use the data in the accompanying table to answer the question. Minutes Spent in Cell Cycle Phases Cell Type G1 S G2 M Beta 18 24 12 16 Delta 100 1 0 0 Gamma 18 48 14 20 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? A) Delta cells contain no DNA. B) Delta cells are in the G0 phase. C) Delta cells divide in the G1 phase. D) Delta cells contain no RNA.

B) Delta cells are in the G0 phase.

Cell A has half as much DNA as cells B, C, and D in a mitotically active tissue. Cell A is most likely in ... A) G2. B) G1. C) metaphase. D) prophase.

B) 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? A) S B) G2 C) G0 D) G1

B) G2

In the figure, G1 is represented by which numbered part(s) of the cycle? A) IV B) I and V C) II D) III

B) I and V

Which of the following molecules is released by platelets in the vicinity of an injury? A) Cdk B) PDGF C) cyclin D) MPF

B) PDGF

How is plant cell cytokinesis different from animal cell cytokinesis? A) Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase. B) Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow. C) The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells. D) The contractile filaments found in plant cells are structures composed of carbohydrates; the cleavage furrow in animal cells is composed of contractile proteins.

B) Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow.

What would you expect to happen if MPF (maturation-promoting factor) is introduced into immature frog oocytes that are arrested in G2? A) The cells would begin DNA synthesis. B) The cells would enter mitosis. C) The cells would enter G0. D) The cells would remain arrested in G2.

B) The cells would enter mitosis.

Once a cell enters mitosis, the molecules that activate division must be turned off. What happens to MPF during mitosis? A) The Cdk component of MPF is degraded. B) The cyclin component of MPF is degraded. C) It is phosphorylated by a Cdk, which inactivates it. D) It is completely degraded.

B) The cyclin component of MPF is degraded.

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? A) How many cells are produced by the culture per hour? B) What is the length of the S phase of the cell cycle? C) How many picograms of DNA are made per cell cycle? D) When do spindle fibers attach to chromosomes?

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

A cleavage furrow is ________. A) a ring of vesicles forming a cell plate B) a groove in the plasma membrane between daughter nuclei C) the separation of divided prokaryotes D) the space that is created between two chromatids during anaphase

B) a groove in the plasma membrane between daughter nuclei

Metaphase is characterized by ________. A) separation of the centromeres B) alignment of chromosomes on the equator of the cell C) cytokinesis D) separation of sister chromatids

B) alignment of chromosomes on the equator of the cell

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? A) centromere B) centrosome C) centriole D) kinetochore

B) centrosome

If the cell whose nuclear material is shown in the figure continues toward completion of mitosis, which of the following events would occur next? A) spindle fiber formation B) formation of telophase nuclei C) synthesis of chromatids D) nuclear envelope breakdown

B) formation of telophase nuclei

Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1.5 times more DNA than G1 phase cells. The cells of this group are... A) between the G1 and S phases in the cell cycle B) in the S phase of the cell cycle C) in the M phase of the cell cycle D) in the G2 phase of the cell cycle

B) in the S phase of the cell cycle

Besides the ability of some cancer cells to over proliferate, which of the following situations might logically result in a tumor? A) failure of cells to enter S phase B) lack of appropriate cell death C) changes in the order of cell cycle stages D) inability to form spindles

B) lack of appropriate cell death

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 ________. A) G2 B) metaphase C) prophase D) telophase

B) metaphase

Which of the following does not occur during mitosis? A) separation of sister chromatids B) replication of the DNA C) spindle formation D) condensation of the chromosomes

B) replication of the DNA

Anchorage dependence of animal cells in vitro or in vivo depends on which of the following? A) attachment of spindle fibers to centrioles B) response of the cell cycle controls to signals from the plasma membrane C) the binding of cell-surface phospholipids to those of adjoining cells D) response of the cell cycle controls to the binding of cell-surface phospholipids

B) response of the cell cycle controls to signals from the plasma membrane

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in binary fission. Its function is analogous to ________. A) the mitotic spindle of eukaryotic cells B) the cleavage furrow of eukaryotic animal cells C) the cell plate of eukaryotic plant cells D) the microtubule-organizing center of eukaryotic cells

B) the cleavage furrow of eukaryotic animal cells

Which of the following molecules is a protein maintained at steady levels throughout the cell cycle that requires cyclin to become catalytically active? A. MPF B. Cdk C. Cyclin D. PDGF

B. Cdk

The beginning of anaphase is indicated by which of the following processes? A. Loss of kinetochores from the chromatids. B. Enzymatic cleavage of cohesion C. Attachment of sister chromatids to each other by cohesion. D. Disappearance of the nuclear membrane

B. Enzymatic cleavage of cohesion

Starting with a fertilized egg (zygote), a series of six cell divisions would produce an early embryo with how many cells? A) 32 B) 16 C) 64 D) 12

C) 64

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. A) As cells become more numerous, they begin to squeeze against each other, restricting their size and ability to allow cell growth. B) 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. C) As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth. D) 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) As cells become more numerous, the amount of required growth factors and nutrients per cell becomes insufficient to allow for cell growth.

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? A) Cancer cells are no longer density-dependent. B) Cancer cells are no longer anchorage-dependent. C) Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities. D) Transformation introduces new chromosomes into cells.

C) Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.

Eukaryotic chromosomes are composed of which of the following macromolecules? A) DNA and phospholipids B) DNA and RNA C) DNA and proteins D) DNA only

C) DNA and proteins

What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis? A) D B) B C) E D) C

C) E

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? A) Formation of a cleavage furrow B) Nuclear envelope breakdown C) Shortening of microtubules D) Elongation of microtubules

C) Shortening of microtubules

Exposure of zebrafish nuclei to cytosol isolated from eggs at metaphase of mitosis 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? A) They assist in the migration of centrosomes to opposite sides of the nucleus. B) They are involved in chromosome condensation. C) They are involved in the disassembly of the nuclear envelope. D) They enable the attachment of the spindle microtubules to kinetochore regions of the centromere.

C) They are involved in the disassembly of the nuclear envelope.

Several organisms, primarily protists, have what are called intermediate mitotic organization. These protists are intermediate in what sense? A) They reproduce by binary fission in their early stages of development and by mitosis when they are mature. B) They use mitotic division but only have circular chromosomes. C) They maintain a nuclear envelope during division. D) None of them form spindles.

C) They maintain a nuclear envelope during division.

In the cells of many eukaryotic species, the nuclear envelope has to disappear to permit which of the following events in the cell cycle? A) condensation of the chromosomes B) separation of the centrosomes C) attachment of microtubules to kinetochores D) DNA synthesis

C) attachment of microtubules to kinetochores

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? A) spindle attachment to kinetochores B) movement of chromosomes to the poles during anaphase C) cleavage furrow formation and cytokinesis D) spindle formation

C) cleavage furrow formation and cytokinesis

One difference between cancer cells and normal cells is that cancer cells A) are arrested at the S phase of the cell cycle. B) cannot function properly because they are affected by density-dependent inhibition. C) continue to divide even when they are tightly packed together. D) are unable to synthesize DNA.

C) continue to divide even when they are tightly packed together.

At which phase of the cell cycle do centrioles begin to move apart in animal cells? A) anaphase B) metaphase C) prophase D) telophase

C) prophase

Motor proteins require which of the following structures of molecules to function in the movement of chromosomes towards the poles of the mitotic spindle? A. Intact cohesin B. Intact centromeres C. ATP as an energy source D. a microtubule-organizing center

C. ATP as an energy source

If a cell at metaphase of mitosis contains 20 sister chromatids, how many chromosomes will be present in a G1 cell? A) 5 B) 20 C) 40 D) 10

D) 10

In the figure, which number represents DNA synthesis? A) IV B) I C) III D) II

D) II

In the figure, MPF reaches its highest concentration during this stage. A) IV B) I C) II D) III

D) III

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable? A) It is safe enough to limit all apoptosis. B) It does not alter metabolically active cells. C) It interferes with cells entering G0. D) It interferes with rapidly dividing cells.

D) It interferes with rapidly dividing cells.

Early observations of a cultured cell line indicated that the cells did not exhibit either density-dependent inhibition or anchorage dependence. What do these observations suggest about this cell line? A) The cells follow an altered series of cell cycle phases. B) The cells have nonfunctional MPF. C) The cells are unable to form spindle microtubules. D) The cells show characteristics of tumors.

D) The cells show characteristics of tumors.

Several organisms, primarily protists, have what are called intermediate mitotic organization. What is the most probable hypothesis about these intermediate forms of cell division? A) They represent a form of cell reproduction that must have evolved completely separately from those of other organisms. B) They rely on totally different proteins for the processes they undergo. C) They may be more closely related to plant forms that also have unusual mitosis. D) They show some but not all of the evolutionary steps toward complete mitosis.

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

During which phase of mitosis do the chromatids become chromosomes? A) metaphase B) telophase C) prophase D) anaphase

D) anaphase

What two components constitute an active MPF? A) cyclin and tubulin B) ATP synthetase and a protease C) a growth factor and mitotic factor D) cyclin and a cyclin-dependent kinase

D) cyclin and a cyclin-dependent kinase

G1 is associated with which of the following cellular events? A) break down of the nuclear membrane B) the beginning of mitosis C) DNA replication D) normal growth and cell function

D) normal growth and cell function