Chapter 12
1) In eukaryotic cells, chromosomes are composed of _____.
A) DNA and RNA
B) DNA only
C) DNA and proteins
D) DNA and phospholipids
Answer: C
2) 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
Answer: A
3) Starting with a fertilized egg (zygote), a series of five cell
divisions would produce an early embryo with how many cells?
A)
8
B) 16
C) 32
D) 64
Answer: C
4) If there are 20 duplicated chromosomes in a cell, how many
centromeres are there? A) 10
B) 20
C) 30
D) 40
Answer: B
5) 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 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
6) The first gap in the cell cycle (G1) corresponds to _____.
A) normal growth and cell function
B) the phase in which DNA
is being replicated
C) the beginning of mitosis
D) the
phase between DNA replication and the M phase
Answer: A
7) 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 _____.
A) microtubulere
B) centrosome
C) centromere
D) kinetochore
Answer: B
8) In human and many other eukaryotic species' cells, the nuclear
membrane has to disappear to permit _____.
A) cytokinesis
B) the attachment of microtubules to kinetochores
C) the splitting of the centrosomes
D) the disassembly of
the nucleolus
Answer: B
9) The mitotic spindle is a microtubular structure that is involved in _____.
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
Answer: D
10) Metaphase is characterized by _____.
A) aligning of
chromosomes on the equator
B) splitting of the centromeres
C) cytokinesis
D) separation of sister chromatids
Answer: A
11) Kinetochore microtubules assist in the process of splitting centromeres by _____.
A) using motor proteins to split the centromere at specific
arginine residues
B) creating tension by pulling toward
opposite poles
C) sliding past each other like actin filaments
D) phosphorylating the centromere, thereby changing its conformation
Answer: B
12) Some cells 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.
Answer: C
13) 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 phospholipids.
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.
Answer: B
14) FtsZ is a bacterial cytoskeletal protein that forms a contractile
ring involved in bacterial cytokinesis. 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
Answer: A
15) At which phase are centrioles beginning to move apart in animal cells?
A) anaphase
B) prometaphase
C) metaphase
D) prophase
Answer: D
16) If there are 20 centromeres in a cell at anaphase, how many
chromosomes are there in each daughter cell following
cytokinesis?
A) 10
B) 20
C) 40
D) 80
Answer: A
17) 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 _____.
A)
the structure of the mitotic spindle
B) anaphase
C)
formation of the centrioles
D) chromatid assembly
Answer: A
18) Which of the following are primarily responsible for cytokinesis
in plant cells but not in animal cells?
A) kinetochores
B)
Golgi-derived vesicles
C) actin and myosin
D) centrioles and centromeres
Answer: B
19) Movement of the chromosomes during anaphase would be most
affected by a drug that prevents _____.
A) nuclear envelope
breakdown
B) elongation of microtubules
C) shortening of microtubules
D) formation of a cleavage furrow
Answer: C
20) 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) M
Answer: C
21) 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?
A) 8; 8
B) 8; 16
C) 16; 8
D) 16; 16
Answer: D
22) The beginning of anaphase is indicated by which of the following?
A) Chromatids lose their kinetochores.
B) Cohesin attaches
the sister chromatids to each other.
C) Cohesin is cleaved enzymatically.
D) Spindle microtubules begin to polymerize.
Answer: C
23) During which phase of mitosis do the chromatids become chromosomes?
A) telophase
B) anaphase
C) prophase
D) metaphase
Answer: B
24) 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
Answer: C
27) 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?
A) spindle fiber formation
B)
nuclear envelope breakdown
C) formation of telophase nuclei
D) synthesis of chromatids
Answer: C
Several organisms, primarily protists, have what are called intermediate mitotic organization.
32) 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.
Answer: C
Several organisms, primarily protists, have what are called intermediate mitotic organization.
33) What is the most probable hypothesis about these intermediate
forms of cell division?
A) They represent a form of cell
reproduction, which 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.
Answer: D
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.
34) 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?
Answer: 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 and introduced these into the culture of dividing human cells at specific times.
35) 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 _____.
A) the presence of the
pathogen made the experiments too contaminated to trust the
results
B) infection causes lymphocytes to divide more
rapidly
C) infection causes cell cultures in general to
reproduce more rapidly
D) infection causes lymphocyte cultures
to skip some parts of the cell cycle
Answer: B
36) 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) an animal cell in the S phase of the cell cycle
D) a plant cell in metaphase
Answer: B
37) Which of the following does NOT occur during mitosis?
A) condensation of the chromosomes
B) replication of the
DNA
C) spindle formation
D) separation of the spindle poles
Answer: B
38) 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?
A) spindle formation
B) spindle attachment
to kinetochores
C) cell elongation during anaphase
D) cleavage furrow
formation and cytokinesis
Answer: D
39) Motor proteins require which of the following 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) synthesis of cohesin
Answer: C
41) Neurons and some other specialized cells divide infrequently because they _____.
A) no longer have active nuclei
B) have entered into G0
C) can no longer bind Cdk to cyclin
D) show a drop in MPF concentration
Answer: B
42) MPF is a dimer consisting of _____.
A) a growth factor and mitotic factor
B) ATP synthetase and a
protease
C) cyclin and tubulin
D) cyclin and a cyclin-dependent kinase
Answer: D
43) Cyclin-dependent kinase (Cdk) is _____.
A) inactive, or
"turned off," in the presence of cyclin
B) present
only during the S phase of the cell cycle
C) the enzyme that
catalyzes the attachment of chromosomes to microtubules
D) an enzyme that attaches phosphate groups to other proteins
Answer: D
44) What happens if MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2?
A) Nothing happens.
B) The cells undergo meiosis.
C)
The cells enter mitosis.
D) Cell differentiation is triggered.
Answer: C
45) Once a cell completes mitosis, molecular division triggers must
be turned off. What happens to MPF during mitosis?
A) It is
completely degraded.
B) It is exported from the cell.
C) The cyclin component of MPF is degraded.
D) The Cdk
component of MPF is degraded and exported from the cell.
Answer: C
46) 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) prometaphase
D) metaphase
Answer: D
47) Which of the following is released by platelets in the vicinity of an injury?
A) PDGF
B) MPF
C) cyclin
D) Cdk
Answer: A
48) Which of the following 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
Answer: C
49) Which of the following 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
Answer: D
50) Which of the following triggers the cell's passage past the G2 checkpoint into mitosis? A) PDGF
B) MPF
C) cyclin
D) Cdk
Answer: B
51) The cyclin component of MPF is destroyed toward the end of which phase?
A) G1
B) S
C) G2
D) M
Answer: D
53) Density-dependent inhibition is explained by which of the
following?
A) As cells become more numerous, they begin to
squeeze against each other, restricting their size and ability to
produce control factors.
B) As cells become more numerous, the
cell surface proteins of one cell contact the adjoining cells and they
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, eventually slowing down metabolism.
Answer: B
54) Besides the ability of some cancer cells to overproliferate, what
else could 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) inability of chromosomes to
meet at the metaphase plate
Answer: B
55) 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
Answer: B
56) A research team began a study of a cultured cell line. Their
preliminary observations showed them that the cell line did not
exhibit either density-dependent inhibition or anchorage dependence.
What could they conclude right away?
A) The cells are unable to
form spindle microtubules.
B) They have altered the series of cell cycle phases.
C) The
cells show characteristics of tumors.
D) They were originally
derived from an elderly organism.
Answer: C
57) 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.
Answer: D
58) 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.
Answer: C
59) 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?
A) They enable the attachment of the spindle microtubules to
kinetochore regions of the centromere.
B) They are involved in
the disassembly and dispersal of the nucleolus.
C) They are
involved in the disassembly of the nuclear envelope.
D) They assist in the movement of the centrosomes to opposite sides of the nucleus
Answer: C
60) 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.
Answer: C