bio 12 Flashcards

Eukaryotic chromosomes are composed of which of the following macromolecules?

A) DNA and RNA
B) DNA only
C) DNA and proteins

D) DNA and phospholipids

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

A) 12
B) 16

C) 32
D) 64

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) 5
B) 10

C) 20
D) 40

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?
A) between the G1 and S phases in the cell cycle

B) in the G2 phase of the cell cycle

C) in the M phase of the cell cycle
D) in the S phase of the cell cycle Answer: D

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) centriole
B) centrosome

C) centromere
D) kinetochore

G1 is associated with which of the following cellular events?

A) normal growth and cell function
B) DNA replication
C) the beginning of mitosis
D) break down of the nuclear membrane

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) DNA synthesis
B) attachment of microtubules to kinetochores

C) separation of the centrosomes
D) condensation of the chromosomes

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

In what way do kinetochore microtubules facilitate the process of splitting the centromeres? A) They use motor proteins to hydrolyze the centromere at specific arginine residues.
B) They create tension by pulling toward opposite poles.
C) They slide past each other like actin microfilaments.

D) They phosphorylate the centromere, thereby changing its conformation.

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

D) separation of sister chromatids

Certain cell types normally have several nuclei per cell. How could such multinucleated cells be explained?
A) The cell underwent repeated cytokinesis but no mitosis.
B) The cell underwent repeated mitosis with simultaneous cytokinesis.

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

D) The cell had multiple S phases before it entered mitosis.

How is plant cell cytokinesis different from animal cell cytokinesis?
A) 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.
C) The structural proteins of plant cells separate the two cells; in animal cells, a cell membrane separates the two daughter cells.
D) Plant cells divide after metaphase but before anaphase; animal cells divide after anaphase.

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

C) the mitotic spindle of eukaryotic cells
D) the microtubule-organizing center of eukaryotic cells

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

D) prophase

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) 5
B) 10

C) 20
D) 40

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) 10
B) 20

C) 40
D) 80

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

C) 20
D) 40

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) cytokinesis
C) centriole duplication
D) chromosome condensation

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) nuclear envelope breakdown
B) elongation of microtubules

C) shortening of microtubules
D) formation of a cleavage furrow

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) G1
B) S
C) G2

D) G0

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) 4

B) 8
C) 16
D) 24

The beginning of anaphase is indicated by which of the following processes? A) Loss of kinetochores from the chromatids.
B) Attachment of sister chromatids to each other by cohesin.
C) Enzymatic cleavage of cohesin.

D) Disappearance of the nuclear membrane.

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

D) metaphase

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

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?
A) They reproduce by binary fission in their early stages of development and by mitosis when they are mature.

B) They have circular chromosomes that are segregated by a mitotic spindle.
C) Chromosomes are segregated by a mitotic spindle, but the nuclear envelope remains intact during division.
D) Chromosomes are segregated by attachment to the plasma membrane.

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.

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?

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?

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) The pathogen consumed radiolabeled nucleotides.
B) Infection causes lymphocytes to divide more rapidly.
C) Infection causes lymphocytes to increase in size.
D) Infection causes lymphocyte cultures to skip some parts 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) an animal cell in the process of cytokinesis
B) an animal cell in anaphase of mitosis

C) a plant cell in the process of cytokinesis
D) a plant cell in metaphase of mitosis

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

D) replication of the DNA

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 formation
B) spindle attachment to kinetochores

C) movement of chromosomes to the poles during anaphase D) cleavage furrow formation and cytokinesis

Motor proteins require which of the following structures or molecules to function in the movement of chromosomes toward the poles of the mitotic spindle?
A) intact centromeres
B) a microtubule-organizing center

C) ATP as an energy source
D) intact cohesin

Why do neurons and some other specialized cells divide infrequently? A) They no longer have active nuclei.
B) They have entered into G0.

C) They can no longer degrade cyclins.
D) They no longer produce MPF.

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

D) cyclin and a cyclin-dependent kinase

Which of the following properties is associated with a cyclin-dependent kinase (Cdk)?
A) A Cdk is inactive, or "turned off," in the presence of a cyclin.
B) The number of Cdk molecules increases during the S and G2 phases and decrease during M.

C) A Cdk is an enzyme that catalyzes the attachment of kinetochores to microtubules. D) A Cdk is an enzyme that attaches phosphate groups to other proteins.

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 remain arrested in G2. B) The cells would enter G0.

C) The cells would enter mitosis.
D) The cells would begin DNA synthesis.

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

C) The cyclin component of MPF is degraded. D) The Cdk 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 ________.
A) telophase
B) prophase

C) G2

D) metaphase

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

D) Cdk

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) PDGF
B) MPF

C) cyclin
D) Cdk

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

C) cyclin
D) Cdk

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

mitosis?
A) PDGF
B) MPF
C) cyclin
D) Cdk

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

D) in late M

Density-dependent inhibition is explained by which of the following processes?
A) As cells become more numerous, they begin to squeeze against each other, restricting their size.
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, 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.
D) As cells become more numerous, the level of waste products increases, which slows metabolism and inhibits growth.

Besides the ability of some cancer cells to over proliferate, which of the following situations might logically result in a tumor?
A) changes in the order of cell cycle stages
B) lack of appropriate cell death

C) inability to form spindles
D) failure of cells to enter S phase

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 are unable to form spindle microtubules.

B) The cells follow an altered series of cell cycle phases. C) The cells show characteristics of tumors.
D) The cells have nonfunctional MPF.

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following characteristics is most desirable?
A) It is safe enough to prevent all apoptosis.
B) It does not interfere with metabolically active cells.

C) It specifically inhibits cells entering G0.
D) It specifically inhibits rapidly dividing cells.

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.

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 enable the attachment of the spindle microtubules to kinetochore regions of the centromere.
B) They are involved in chromosome condensation.
C) They are involved in the disassembly of the nuclear envelope.

D) They assist in the migration of centrosomes to opposite sides of the nucleus.

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) an animal cell in the process of cytokinesis.
B) a plant cell in the process of cytokinesis.

C) a bacterial cell dividing.
D) a plant cell in metaphase.

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to
A) disruption of mitotic spindle formation.
B) suppression of cyclin production.

C) myosin denaturation and inhibition of cleavage furrow formation. D) inhibition of DNA synthesis.

One difference between cancer cells and normal cells is that cancer cells A) are unable to synthesize DNA.
B) are arrested at the S phase of the cell cycle.
C) continue to divide even when they are tightly packed together.

D) cannot function properly because they are affected by density-dependent inhibition.

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

D) the accumulation of cyclin.

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

D) cell cycles lacking an S phase.

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

D) spindle formation

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) G1.
B) G2.

C) prophase.
D) metaphase.

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 formation
B) spindle attachment to kinetochores

C) cell elongation during anaphase
D) cleavage furrow formation and cytokinesis