Deck 9: The Cell Cycle

Question 1

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

A)spot desmosomes
B)tubulin and dynein
C)actin and myosin
D)centrioles and centromeres
E)Golgi-derived vesicles

Answer 1

E

Question 2

Which of the following components make(s)up eukaryotic chromatin?

A)condensed DNA only
B)DNA and RNA
C)DNA and carbohydrates
D)DNA and proteins
E)DNA and ribosomes

Answer 2

D

Question 3

What will be the result if a eukaryotic cell completes mitosis but does not undergo cytokinesis?

A)two cells,one cell containing two nuclei and a second cell without a nucleus
B)two cells,each cell with half of the genetic material of the parent cell
C)one cell with two nuclei,each containing half of the genetic material of the parent cell
D)one cell with one nucleus containing half of the genetic material of the parent cell
E)one cell with two nuclei,each identical to the nucleus of the parent cell

Answer 3

E

Question 4

Beginning with a fertilized egg (zygote),how many cells would be present in an embryo following a series of five cell divisions?

A)4
B)8
C)16
D)32
E)64

Question 5

Somatic cells in elephants have 56 chromosomes.How many chromosomes would be carried by the gametes produced by elephants?

A)14
B)28
C)56
D)112

Question 6

Following DNA replication,each eukaryotic chromosome consists of two identical DNA molecules known as

A)daughter chromosomes
B)sister chromatids
C)sister cohesins
D)sister chromatins

Question 7

What is a cleavage furrow?

A)a ring of vesicles forming a cell plate
B)an indentation between daughter prokaryotic cells
C)a groove in the plasma membrane between daughter nuclei
D)the metaphase plate where chromosomes attach to the spindle

Question 8

Taxol is an anticancer drug extracted from the Pacific yew tree that binds to microtubules and prevents their depolymerization.Which phase of mitosis or cell division would be inhibited by treatment with Taxol?

A)prophase
B)prometaphase
C)metaphase
D)anaphase
E)cytokinesis

Question 9

You have the technology necessary to measure each of the following in a sample of animal cells: carbohydrates,organelle density,picograms of DNA,cell wall components,and enzymatic activity.Which of the following cell characteristics would you expect to increase significantly between a cell in mitosis and one just beginning G₁?

A)organelle density
B)cell wall components
C)DNA content
D)enzyme activity
E)carbohydrates

Question 10

Humans produce skin cells by mitosis and gametes by meiosis.Which of the following statements about the nuclei of skin cells is correct?

A)They contain half as much DNA as the nuclei of gametes produced by meiosis.
B)They contain the same amount of DNA as the nuclei of gametes produced by meiosis.
C)They contain twice as much DNA as the nuclei of gametes produced by meiosis.
D)They contain four times as much DNA as the nuclei of gametes produced by meiosis.

Question 11

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 12 picograms of DNA per nucleus.How many picograms of DNA would be found in a nucleus at the end of G₁ and the end of G₂?

A)12;12
B)12;24
C)24;12
D)24;24

Question 12

The beginning of anaphase is indicated by which of the following events?

A)loss of kinetochores from sister chromatids
B)enzymatic cleavage of cohesin
C)joining of the sister chromatids to each other by cohesin
D)polymerization of spindle microtubules

Question 13

Where do the microtubules of the spindle originate during mitosis in animal cells?

A)centromere
B)centrosome
C)centriole
D)chromatid
E)kinetochore

Question 14

If there are 20 centromeres in a cell at anaphase of mitosis,how many chromosomes are there in each daughter cell following cytokinesis?

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

Question 15

Movement of the chromosomes during anaphase would be most affected by a drug that prevents which of the following processes?

A)nuclear envelope breakdown
B)cell wall formation
C)elongation of microtubules
D)shortening of microtubules
E)formation of a cleavage furrow

Question 16

At which phase of mitosis do the sister chromatids become daughter chromosomes?

A)prophase
B)prometaphase
C)metaphase
D)anaphase
E)cytokinesis

Question 17

A plant-derived protein known as colchicine can be used to poison cells by blocking the formation of the mitotic spindle.Which of the following would result if colchicine is added to a sample of cells in G₂?

A)The cells would immediately die.
B)The cells would be unable to begin M,and the cell cycle would arrest in G₂.
C)The nuclear membrane would break down,but chromosomes would fail to condense and the cell cycle would arrest in early prophase.
D)Chromosomes would condense but fail to align at the metaphase plate,and the cell cycle would arrest at this point.

Question 18

A cell in G2 of the cell division cycle contains 20 chromatids.How many centromeres are present in this cell?

A)10
B)20
C)30
D)40
E)80

Question 19

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 would the nucleus contain 6 picograms of DNA?

A)G₀
B)G₁
C)S
D)G₂

Question 20

A group of cells is assayed for DNA content immediately before beginning mitosis and is found to have an average of 16 picograms of DNA per nucleus.How many picograms of DNA would be found in a cell nucleus following completion of mitosis and cytokinesis?

A)4
B)8
C)16
D)32

Question 21

Researchers studying a new cultured cell line observed that the cells did not exhibit either density-dependent inhibition or anchorage dependence.What could they conclude right away?

A)The cells originated in the nervous system.
B)The cells show characteristics of tumors.
C)The cells have altered series of cell cycle phases.
D)The cells were originally derived from an elderly organism.

Question 22

Density-dependent inhibition is explained by which of the following statements?

A)As cells become more numerous,they begin to squeeze against each other,restricting their size and ability to produce growth factors.
B)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.
C)As cells become more numerous,the cell surface proteins of adjacent cells bind to each other and send signals that inhibit cell division.
D)As cells become more numerous,the level of waste products increases,eventually slowing down metabolism.

Question 23

The unlettered circle at the top of the figure above 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-E show various combinations of these chromosomes.What is the correct chromosomal condition for a nucleus at prophase of mitosis?

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

Question 24

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 limit all apoptosis.
B)It does not affect metabolically active cells.
C)It only attacks cells that are density dependent.
D)It targets only rapidly dividing cells.

Question 25

When a cell is in late anaphase of mitosis,which of the following may be observed?

A)a clear area in the center of the dividing cell
B)decondensing chromosomes clustered at the poles
C)individual chromatids beginning to separate from one another
D)chromosomes clustered tightly at the center of the dividing cell
E)nuclear envelopes forming at the poles

Question 26

The unlettered circle at the top of the figure above 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-E show various combinations of these chromosomes.Which image displays the chromosomal composition of one daughter nucleus at telophase of mitosis?

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

Question 27

During which phase of mitosis in animal cells do centrioles begin to move apart?

A)prophase
B)prometaphase
C)metaphase
D)anaphase
E)telophase

Question 28

Which of the following molecules is released by human platelets in the vicinity of a cut to stimulate proliferation of skin cells?

A)PDGF
B)kinesin
C)protein kinase
D)cyclin

Question 29

Progression through the M phase checkpoint is stimulated by a complex that does which of the following things?

A)activates separase to cleave cohesin proteins
B)activates separase to modify kinetochores
C)activates motor molecules at the centromere to begin disassembly of spindle microtubules
D)activates assembly of spindle microtubules

Question 30

Which is the first checkpoint in the cell cycle that will cause a cell to exit the cycle if this point is not passed?

A)G₀
B)G₁
C)G₂
D)S
E)M

Question 31

Diatoms and some yeasts are unicellular eukaryotes that 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 have circular chromosomes that are segregated by attachment to the plasma membrane.
B)They have circular chromosomes that are segregated by attachment to spindle microtubules.
C)Chromosomes are not condensed during nuclear division.
D)The nuclear envelope remains intact during division.

Question 32

Most animal cells exhibit anchorage dependence,which means that in order to divide,

A)all chromosomes must be attached to spindle microtubules.
B)nonkinetochore microtubules from opposite poles must overlap and be attached by motor proteins.
C)cell-surface phospholipids must be attached to those of adjoining cells.
D)cells must be attached to a substrate or extracellular matrix of a tissue.

Question 33

The unlettered circle at the top of the figure above 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-E show various combinations of these chromosomes.What is the correct chromosomal condition for a nucleus in G1 of the cell division cycle?

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

Question 34

Why do most cells in the human body divide infrequently?

A)They no longer have active nuclei.
B)They no longer carry receptors for signal molecules.
C)They have exited the cell cycle and entered G₀.
D)They have defective microtubules.

Question 35

Which of the following characteristics is associated with cancer cells?

A)They exhibit density-dependent inhibition when growing in culture.
B)They must be attached to a substrate to divide in culture.
C)They evade the normal controls that trigger programmed cell death.
D)They stop dividing in culture when growth factors are depleted.

Question 36

Where are the motor proteins that move chromosomes toward the poles of the mitotic spindle located?

A)on the kinetochores only
B)at the centrosomes only
C)on the kinetochores and at the centrosomes
D)along the length of kinetochore microtubules only

Question 37

Researchers established a number of cultured cell lines derived from different tumors.How might they determine which ones are malignant?

A)Identify the ones that grow in a single layer in culture.
B)Identify the ones with elevated rates of apoptosis.
C)Identify the ones with aberrant chromosome number or structure.
D)Identify the ones with elongated cell cycles.

Question 38

Cells from advanced malignant tumors frequently have very abnormal chromosomes as well as an abnormal number of chromosomes.What might explain the association between malignant tumors and chromosomal abnormalities?

A)Cancer cells replicate chromosomes multiple times per cell cycle.
B)Cancer cells are no longer anchorage dependent.
C)Cell cycle checkpoints are not in place to stop cells with chromosome abnormalities.
D)Cells with abnormal chromosomes have increased metabolism.

Question 39

Besides the ability of some cancer cells to divide uncontrollably,what else might logically result in formation of a tumor?

A)enhanced anchorage dependence
B)changes in the order of cell cycle stages
C)lack of appropriate cell death
D)inability to form spindles

Question 40

The cell cycle is regulated at the molecular level by a set of proteins known as

A)ATPases.
B)separase proteins.
C)cohesins.
D)cyclins.

Question 41

The data in the table above 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.Which of the following is the most plausible explanation for the difference in time spent in S phase by beta and gamma?

A)Gamma is unicellular,and beta is multicellular.
B)Beta is tetraploid,and gamma is diploid.
C)Gamma contains more DNA than beta.
D)Beta reproduces asexually,and gamma reproduces sexually.

Question 42

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.

Question 43

In the figure above,which numbered segment(s)of the cycle would contain cells in G₂?

A)I and V
B)II and IV
C)III only
D)IV only
E)III and IV

Question 44

The data in the table above 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.The best conclusion concerning delta is that the cells

A)contain no DNA.
B)contain only one chromosome that is very small.
C)are actually in the G₀ phase.
D)synthesize DNA in the G₁ phase

Question 45

In the figure above,which numbered segment(s)of the cycle would include cells at some phase of mitosis?

A)II only
B)III only
C)IV only
D)III and IV
E)II and III

Question 46

In the figure above,which numbered segment(s)of the cycle would contain cells at metaphase of mitosis?

A)I and V
B)II only
C)III only
D)II and III

Question 47

A particular cell has half as much DNA as some other cells in a mitotically active tissue.The cell in question is most likely in

A)G₁.
B)G₂.
C)prophase.
D)metaphase.

Question 48

If the cell whose nuclear material is shown in the figure above continues toward completion of mitosis,which of the following events would occur next?

A)cell membrane synthesis
B)alignment of chromosomes at the metaphase plate
C)segregation of daughter chromosomes toward the poles
D)formation of telophase nuclei
E)synthesis of sister chromatids

Question 49

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.

Question 50

If cells are provided with nucleotides labeled with a radioactive isotope of hydrogen (³H),newly synthesized DNA will be radioactively labeled.In a set of experiments,a student-faculty research team introduced labeled T nucleotides into a culture of dividing human cells at specific times.Following a 30-minute incubation with the radiolabeled nucleotides,cells were lysed,and the DNA was isolated and tested for presence of radioactivity.Which of the following questions might be answered by such a method?

A)How many cells are produced by the culture per hour?
B)What is the duration of the S phase of the cell cycle?
C)What is the duration of mitosis?
D)How many picograms of DNA are contained in each nucleus?

Question 51

Several organisms,including some diatoms and yeasts,have intermediate mitotic organization.Which of the following is the most probable hypothesis regarding these intermediate forms of cell division?

A)They represent a form of cell reproduction that must have evolved completely separately from that present in most eukaryotes.
B)These species are not closely related other diatoms and yeasts,even though they may be similar in outward appearance.
C)They rely on totally different proteins for the processes they undergo.
D)They show some but not all of the evolutionary steps toward complete mitosis.

Question 52

In the figure above,which numbered segment(s)of the cycle represent G₁?

A)I and V
B)II and IV
C)III only
D)IV only

Question 53

If cells are provided with nucleotides labeled with a radioactive isotope of hydrogen (³H),newly synthesized DNA will be radioactively labeled.In a set of experiments,a student-faculty research team introduced labeled T nucleotides into cultures of dividing human lymphocytes at specific times.A pathogen was introduced into one culture prior to the start of the experiment,and another culture was left untreated as a control.Following a 24-hour incubation with the radiolabeled nucleotides,cells were lysed,and the DNA was isolated and tested for presence of radioactivity.The research team found that lymphocytes exposed to a pathogen incorporated three times the amount of labeled nucleotide as the control.Which of the following hypotheses might explain these observations?

A)The pathogen thrived in culture and incorporated the excess nucleotide.
B)Infection causes lymphocyte cultures to skip some parts of the cell cycle.
C)Infection causes lymphocytes to reproduce more rapidly.
D)Infection causes cell cultures in general to reproduce more rapidly.

Question 54

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

Question 55

In the figure above,which numbered segment(s)of the cycle represent the period during which the chromosomes are replicated?

A)I and V
B)II only
C)III only
D)IV only
E)II and IV

Question 56

In the figure above,which numbered segment(s)of the cycle represent DNA synthesis?

A)I and V
B)II only
C)III only
D)IV only
E)II and IV

Question 57

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