Ch. 12 Biology Mastering
Amount of DNA per nucleus over the cell division cycle.Which region of the accompanying figure represents S phase? a) I b) II c) III d) IV
b) II
In a diploid cell with four chromosome pairs (2n = 8), how many centromeres will be found in a nucleus at G2 of the cell division cycle? a) 8 b) 4 c) 32 d) 16
a) 8
Which of the following structures or molecules is required in order for motor proteins to facilitate movement of chromosomes toward the poles in mitosis? a) ATP as an energy source b) actin microfilaments c) intact centromeres d) intact cohesin
a) ATP as an energy source
Progression beyond the G2 checkpoint into mitosis is triggered by which of the following molecules? a) Cdk b) MPF c) cyclin d) PDGF
b) MPF
How do cancer cells differ from normal cells? a) Cancer cells may be immortal. b) Cultured cancer cells exhibit anchorage dependence. c) Cancer cells trigger chromosomal changes in surrounding cells.
a) Cancer cells may be immortal.
Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. Which of the following best explains the association between malignant tumors and chromosomal abnormalities? a) Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities. b) Cancer cells are no longer anchorage-dependent. c) Cancer cells are no longer density-dependent. d) Transformation introduces new chromosomes into cells.
a) Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
Which statement provides the best description of the interphase portion of the cell cycle? a) During interphase, a cell is metabolically active. b) Interphase is a resting stage prior to cell division. c) Interphase is a brief period between mitosis and chromosome duplication.
a) During interphase, a cell is metabolically active.
If a eukaryotic cell is in the G1 phase of the cell cycle, which statement about the cell's chromosomes must be correct? a) Each chromosome is made of a complex of DNA and associated proteins. b) Each chromosome consists of two identical chromatids. c) The chromosomes are preparing for DNA synthesis.
a) Each chromosome is made of a complex of DNA and associated proteins.
The cell cycle control systems of cancer cells differ from those of normal cells. Select the best explanation for this fact. a) Genetic changes alter the function of the cancer cell's protein products. b) Cancer cells divide excessively and invade other tissues. c) Cancer cells are immortal.
a) Genetic changes alter the function of the cancer cell's protein products.
The unlettered circle at the top of the accompanying figure shows a diploid nucleus with four unreplicated chromosomes. The circles labeled 1 to 5 show various combinations of these chromosomes. Which chromosomal configuration would be observed at prometaphase of mitosis? a) II b) IV c) III d) V
a) II
Which of the following characteristics would be most important for a chemotherapeutic drug designed to treat cancer cells? a) It specifically inhibits the cell division cycle in rapidly dividing cells. b) It specifically inhibits cells entering G0. c) It is safe enough to prevent all apoptosis. d) It does not interfere with metabolically active cells.
a) It specifically inhibits the cell division cycle in rapidly dividing cells.
Which of the following statements best describes a cleavage furrow? a) a groove in the plasma membrane between daughter nuclei b) the separation of divided prokaryotes c) a ring of vesicles forming a cell plate d) the space that is created between two chromatids during anaphase
a) a groove in the plasma membrane between daughter nuclei
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol prevents microtubule depolymerization, which interferes with which of the following processes? a) chromosome separation b) centriole duplication c) cytokinesis d) chromosome condensation
a) chromosome separation
The drug cytochalasin B blocks the polymerization of actin microfilaments. Which of the following events of the cell cycle in animal cells would be most directly disrupted by cytochalasin B? a) cleavage furrow formation and cytokinesis b) spindle formation c) spindle attachment to kinetochores d) movement of chromosomes to the poles during anaphase
a) cleavage furrow formation and cytokinesis
Which of the following molecules is synthesized at specific times during the cell cycle and forms an active complex with a kinase? a) cyclin b) PDGF c) Cdk d) MPF
a) cyclin
Which of the following pairs of molecules make up an active MPF? a) cyclin and a cyclin-dependent kinase b) ATP synthetase and a protease c) a growth factor and mitotic factor d) cyclin and tubulin
a) cyclin and a cyclin-dependent kinase
Students in a biology lab isolated cells in various phases of the cell cycle. A population of cells that have twice the DNA of G1 phase cells was most likely isolated from which of the following part of the cell cycle? a) in the G2 phase b) immediately after cytokinesis c) between the G1 and S phase d) at the beginning of the S phase
a) in the G2 phase
Besides the ability of some cancer cells to over proliferate, which of the following situations is most likely to result in a tumor? a) lack of appropriate cell death b) inability to form spindles c) failure of cells to enter S phase d) changes in the order of cell cycle stages
a) lack of appropriate cell death
Which of the following events occurs during interphase of the cell cycle? a) replication of the DNA b) spindle formation c) separation of the spindle poles d) condensation of the chromosomes
a) replication of the DNA
Why do some species employ both mitosis and meiosis, whereas other species use only mitosis? a) they need both if they are reproducing sexually b) a single-celled organism only needs mitosis c) if they produce large numbers of sperm cells they do not require meiosis d) if they produce egg cells they do not require mitosis e) they need meiosis if the cells are producing organs such as ovaries
a) they need both if they are reproducing sexually
Amount of DNA per nucleus over the cell division cycle.Which numbered regions of the accompanying figure represent the DNA content associated with cells at metaphase? a) II only b) III only c) IV only d) II and IV
b) III only
A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. How many chromatids does it contain? a) 23 or 46, depending on the portion of prophase examined b) 92 c) 23 d) 46 e) 46 or 92, depending on the portion of prophase examined
b) 92
How can a protein outside the cell cause events to happen inside the cell? a) A protein outside the cell can phosphorylate a protein inside the cell, which transduces a signal and causes a response. b) A protein outside the cell can bind to a receptor protein on the cell surface, causing it to change shape and sending a signal inside the cell. c) A protein can pass through the membrane and into the cell, causing signaling inside the cell. d) A protein outside the cell can cause the H+H+ ion concentration outside the cell to be higher, which allows substances to pass into the cell and transduce a signal.
b) A protein outside the cell can bind to a receptor protein on the cell surface, causing it to change shape and sending a signal inside the cell.
Which of the following statements best describes density-dependent inhibition? 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.
Cells will usually divide if they receive the proper signal at a checkpoint in which phase of the cell cycle? a) S b) G1 c) G2 d) M e) cytokinesis
b) G1
Which of the following statements best describes microtubules? a) Microtubules are permanent cellular structures that help the cell to move from place to place. b) Microtubules are made up of subunits of tubulin, and are structures along which substances are transported in the cell. c) Microtubules are fibrous proteins coiled into cables that maintain cell shape and anchor the nucleus. d) Microtubules are made up of subunits of actin, and function in muscle contraction and changes in cell shape.
b) Microtubules are made up of subunits of tubulin, and are structures along which substances are transported in the cell.
What is the best description of the structure of a chromosome in the nucleus of a non-dividing cell? a) Two long DNA molecules wound around each other, with no proteins. b) One long DNA molecule, associated with many proteins. c) Two long DNA molecules wound around each other, associated with many proteins. d) One long DNA molecule, with no proteins.
b) One long DNA molecule, associated with many proteins.
Which of the following statements best describes 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 completely degraded. d) It is phosphorylated by a Cdk, which inactivates it.
b) The cyclin component of MPF is degraded.
Which of the following statements describing kinetochores is correct? a) They attach to the ring of actin along the cytoplasmic surface of the plasma membrane, causing the actin to contract to form the cleavage furrow. b) They are sites at which microtubules attach to chromosomes. c) They are the primary centromere structures that maintain the attachment of the sister chromatids prior to mitosis. d) They are located at the center of the centrosome; their function is to organize tubulin into elongated bundles called spindle fibers e) They interdigitate at the cell's equator and then move apart, causing the cell to elongate.
b) They are sites at which microtubules attach to chromosomes.
What is true of all cancers? a) They are inherited. b) They have escaped normal cell cycle controls. c) They are caused by chemical carcinogens.
b) They have escaped normal cell cycle controls.
Which of the following occurs in binary fission but not in mitosis with cytokinesis? a) following the process, a membrane separates the two copies b) duplicated chromosomes attach to the plasma membrane c) replicated strands of DNA separate d) replication of DNA begins at an origin e) the result produces two nuclei
b) duplicated chromosomes attach to the plasma membrane
At what stage of the cell cycle is the cyclin component of MPF destroyed? a) in late G1 b) in late M c) at mid-S phase d) in early G2
b) in late M
Which of the following cellular events occur in the G1 phase of the cell division cycle? a) DNA replication b) normal growth and cell function c) the beginning of mitosis d) break down of the nuclear membrane
b) normal growth and cell function
The mitotic spindle plays a critical role in which of the following processes? a) triggering condensation of chromosomes b) separation of sister chromatids c) splitting of the cell (cytokinesis) following mitosis d) dissolving the nuclear membrane
b) separation of sister chromatids
Movement of the chromosomes during anaphase would be most directly affected by a drug that prevents which of the following events? a) formation of a cleavage furrow b) shortening of microtubules c) elongation of microtubules d) nuclear envelope breakdown
b) shortening of microtubules
What is the name of the region on duplicated chromosomes where the sister chromatids are most closely attached to each other? a) the centrosome b) the centromere c) the chromatin d) the cohesin
b) the centromere
Which of the following statements describes a characteristic feature of metaphase? a) separation of the centromeres b) cytokinesis c) alignment of chromosomes on the equator of the cell d) separation of sister chromatids
c) alignment of chromosomes on the equator of the cell
If there are 24 centromeres in a cell at anaphase of mitosis, how many chromosomes will be found in each daughter cell following cytokinesis? a) 24 b) 6 c) 12 d) 48
c) 12
If a cell at metaphase of mitosis contains 32 sister chromatids, how many chromosomes will be present in a G1 cell? a) 64 b) 32 c) 16 d) 8
c) 16
A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 10 picograms of DNA per nucleus. Approximately how many picograms of DNA would be found in a nucleus at prophase of mitosis? a) 10 b) 40 c) 20 d) 5
c) 20
Beginning with a fertilized egg (zygote), how many cells will be present in the embryo following five rounds of cell division? a) 10 b) 6 c) 32 d) 16
c) 32
Which of the following molecules is maintained at a relatively constant level throughout the cell cycle but requires a cyclin to become catalytically active? a) cyclin b) PDGF c) Cdk d) MPF
c) Cdk
Certain unicellular eukaryotes, including diatoms and some yeasts, have mechanisms of nuclear division that resemble intermediate steps in the evolution of mitosis. Which of the following is a characteristic feature of nuclear division in these organisms? a) Chromosomes are segregated by attachment to the plasma membrane. b) They reproduce by binary fission in their early stages of development and by mitosis when they are mature. c) Chromosomes are segregated by a mitotic spindle, but the nuclear envelope remains intact during division. d) 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.
Which of the following correctly matches a phase of the cell cycle with its description? a) G2, cell division b) M, duplication of DNA c) G1, follows cell division d) S, immediately precedes cell division e) All of the listed choices are correctly matched.
c) G1, follows cell division
At which point in the accompanying figure does MPF reach its highest activity during the cell division cycle? a) I b) II c) III d) IV
c) III
A research team used a culture of lymphocytes with radioactively labeled T nucleotides to study the cell cycle. They found that the lymphocytes incorporated the labeled nucleotide at a significantly higher rate after a pathogen was introduced into the culture. Which of the following conclusions is most consistent with the results? a) Infection causes lymphocyte cultures to skip some parts of the cell cycle. b) Infection causes lymphocytes to increase in size. c) Infection causes lymphocytes to divide more rapidly. d) The pathogen consumed radiolabeled nucleotides.
c) Infection causes lymphocytes to divide more rapidly.
What effect does phosphorylating a protein have on that protein? a) Phosphorylation adds one or more phosphorus atoms to the protein, allowing it to perform a particular function. b) Phosphorylation adds energy to the protein, allowing it to form ATP from ADP and Pi. c) Phosphorylation changes the shape of the protein, most often activating it. d) Phosphorylation may have no effect at all on the protein.
c) Phosphorylation changes the shape of the protein, most often activating it.
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 are involved in chromosome condensation. b) They are involved in migration of centrosomes to opposite sides of the nucleus. c) They are involved in the disassembly of the nuclear envelope. d) They enable the attachment of spindle microtubules to kinetochores.
c) They are involved in the disassembly of the nuclear envelope.
Which of the following statements best explains how neurons and some other specialized cells divide infrequently? a) They no longer produce MPF. b) They can no longer degrade cyclins. c) They have entered into G0. d) They no longer have active nuclei.
c) They have entered into G0.
Which chromosomal configuration would be observed in one daughter cell after telophase of mitosis? a) II b) III c) V d) IV
c) V
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
c) a plant cell in the process of cytokinesis
Which of the following events characterizes the beginning of anaphase? a) loss of kinetochores from the chromatids b) disappearance of the nuclear membrane c) enzymatic cleavage of cohesin d) attachment of sister chromatids to each other by cohesin
c) enzymatic cleavage of cohesin
Students in a biology lab isolated cells in various phases of the cell cycle. A population of cells that have 1 1/2 times the DNA of G1 phase cells was most likely isolated from which of the following parts of the cell cycle? a) in the M phase b) in the G2 phase c) in the S phase d) between the G1 and S phases
c) in the S phase
Why is it difficult to observe individual chromosomes with a light microscope during interphase? a) they leave the nucleus and are dispersed to other parts of the cell b) the DNA has not been replicated yet c) interphase chromosomes are long, thin strands unlike the condensed chromosomes visible in mitosis d) the spindle must move them to the metaphase plate before they become visible e) sister chromatids do not pair up until division starts
c) interphase chromosomes are long, thin strands unlike the condensed chromosomes visible in mitosis
If all chromosomes are not attached to the mitotic spindle at the M phase checkpoint, the cells would most likely be arrested at which of the following points in the cell division cycle or mitosis? a) G2 b) prophase c) metaphase d) telophase
c) metaphase
At which phase of the cell cycle do centrioles begin to move apart in animal cells? a) metaphase b) telophase c) prophase d) anaphase
c) prophase
Which of the following events would be most likely to produce cells with several nuclei? a) multiple S phases without mitosis b) repeated cytokinesis without mitosis c) repeated mitosis without cytokinesis d) repeated mitosis with simultaneous cytokinesis
c) repeated mitosis without cytokinesis
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 formation b) formation of telophase nuclei c) segregation of daughter chromosomes d) nuclear envelope breakdown
c) segregation of daughter chromosomes
After DNA replication, each duplicated chromosome consists of two of which of the following structures? a) sister chromatins b) daughter nucleosomes c) sister chromatids d) daughter chromosomes
c) sister chromatids
FtsZ is a bacterial protein that forms a contractile ring involved in binary fission. Its function is analogous to which of the following structures in eukaryotic cells? a) the microtubule-organizing center of eukaryotic cells b) the cell plate of eukaryotic plant cells c) the cleavage furrow of eukaryotic animal cells d) the mitotic spindle of eukaryotic cells
c) the cleavage furrow of eukaryotic animal cells
Which of the following is true of benign tumors, but not malignant tumors? a) they migrate from the initial site of transformation to other organs or tissues b) they can divide indefinitely if an adequate supply of nutrients is available c) they remain confined to their original site d) they are the result of the transformation of normal cells e) they have an unusual number of chromosomes
c) they remain confined to their original site
In a diploid cell with four chromosome pairs (2n = 8), how many sister chromatids will be found in a nucleus at prophase of mitosis? a) 4 b) 32 c) 8 d) 16
d) 16
Which of the following properties is associated with a cyclin-dependent kinase (Cdk)? a) The number of Cdk molecules increases during the S and G2 phases and decrease during M. b) A Cdk is inactive, or "turned off," in the presence of a cyclin. 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.
d) A Cdk is an enzyme that attaches phosphate groups to other proteins.
Eukaryotic chromatin is composed of which of the following macromolecules? a) DNA and RNA b) DNA and phospholipids c) DNA only d) DNA and proteins
d) DNA and proteins
The mass of DNA per nucleus in a certain fungus ranges from 4 to 10 picograms. Nuclei with 5 picograms of DNA are most likely derived from cells in which of the following parts of the cell cycle? a) G2 b) early M c) late S d) G1
d) G1
Amount of DNA per nucleus over the cell division cycle.G1 is represented by which numbered part(s) of the cell division cycle in the accompanying figure? a) IV b) III c) II d) I and V
d) I and V
One type of eukaryotic cell (line 1) spends 24 minutes in S phase and another type of cell (line 2) spends 48 minutes in S phase. Which of the following statements is the best explanation for the difference in time spent in S phase by cell lines 1 and 2? a) Line 2 has plant cells and line 1 has animal cells. b) Line 1 cells reproduce by binary fission and line 2 cells reproduce by mitosis and cytokinesis. c) Lines 1 and 2 contain the same amount of DNA. d) Line 2 contains more DNA than line 1.
d) Line 2 contains more DNA than line 1.
Which of the following statements best describes how cytokinesis differs between plant and animal cells? 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) Cytokinesis occurs between metaphase and anaphase in plant cells; it occurs after anaphase in animal cells. 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 deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
d) Plant cells deposit vesicles containing cell wall building blocks on the metaphase plate; animal cells form a cleavage furrow.
Which of the following statements best describes cells in culture that do not exhibit either density-dependent inhibition or anchorage dependence? a) The cells have nonfunctional MPF. b) The cells are unable to form spindle microtubules. c) The cells follow an altered series of cell cycle phases. d) The cells show characteristics of tumors.
d) The cells show characteristics of tumors.
Which of the following statements best describes what would 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 begin DNA synthesis. c) The cells would enter G0. d) The cells would enter mitosis.
d) The cells would enter mitosis.
In which phase of mitosis do the sister chromatids become daughter chromosomes? a) metaphase b) prophase c) telophase d) anaphase
d) anaphase
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) kinetochore c) centromere d) centrosome
d) centrosome
Cytochalasin B is a chemical that disrupts microfilament formation. With which aspect of cell division would cytochalasin B interfere? a) binary fission b) formation of the cell plate c) formation of the mitotic spindle d) cleavage e) DNA replication
d) cleavage
In some organisms, such as certain fungi and algae, cells undergo the cell cycle repeatedly without subsequently undergoing cytokinesis. What would result from this? a) a decrease in chromosome number b) a rapid rate of gamete production c) inability to duplicate DNA d) large cells containing many nuclei e) division of the organism into many cells, most lacking nuclei
d) large cells containing many nuclei