Deck 11: The Cell Cycle

Question 1

Metaphase occurs prior to the splitting of centromeres.It is characterized by

A)aligning of chromosomes on the equator.
B)duplication of centrioles.
C)cytokinesis.
D)disassembly of the nuclear envelope.

Answer 1

A

Question 2

In a culture of cells,it is observed that the cell cycle has arrested (stopped)during the G1 phase.The reason for this could be that

A)not all chromosomes have been replicated.
B)not all components needed for mitosis are present.
C)not all components needed for DNA replication are present.
D)not all chromosomes are attached to mitotic spindles.

Answer 2

C

Question 3

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)disassembly of the nucleolus.
D)separation of sister chromatids.

Answer 3

D

Question 4

The microtubular organizing center found in animal cells is an identifiable structure present during all phases of the cell cycle.Specifically,it is known as which of the following?

A)cell plate
B)centrosome
C)centromere
D)kinetochore

Question 5

Researchers pulsed rapidly dividing cultured cells for 30 minutes with radioactive thymidine.The cells were then exposed to a solution containing non-radiolabeled thymidine.Cells were analyzed at 2-hour intervals.At the 2-hour time point,no cells appeared to be dividing.Only after 4 hours did some labeled cells appear to be in M phase.This result can be explained in the following way:

A)Cultured cells all divide at the same time,and none synthesized DNA during the 30-minute labeling period.
B)The cells were arrested in a nondividing state because of the treatment and could not enter M phase until several hours after the label was removed.
C)Synthesis (S)phase is lengthy-about 12 hours in most cell types-and the radioactive thymidine was not present long enough for most cells to be labeled.
D)There seems to be a gap or a lag in the cell cycle,between the synthesis of DNA and cell division.

Question 6

How might spindle microtubules assist in the process of splitting centromeres?

A)the use of motor proteins to split the centromere at specific arginine residues
B)creating tension by pulling toward opposite poles
C)coding for enzymes involved in the process
D)phosphorylating the centromere,which changes its conformation

Question 7

Following the attachment of spindle microtubules to kinetochores,chromosomes are moved around by

A)myosin motor proteins.
B)histones.
C)elongation and shortening of microtubules.
D)motor activity taking place in the centrosomes.

Question 8

A parent cell divides to form two genetically identical daughter cells in the process of mitosis.For mitosis to take place

A)the parent cell must first be fertilized.
B)the parent cell must replicate its entire genome prior to mitosis.
C)the parent cell must reproduce its DNA during telophase.
D)the parent cell must divide its DNA in half so each daughter cell gets only the genes needed to carry out its functions.In this way,differentiation occurs.

Question 9

How is plant cell cytokinesis different from animal cell cytokinesis?

A)The cleavage furrow in animal cells is composed of protein contractile filaments;the contractile filaments found in plant cells are structures composed of carbohydrates.
B)Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate;animal cells form a cleavage furrow.
C)The structural carbohydrates of the plant cells separate the two cells,whereas in animal cells,a cell membrane separates the two daughter cells.
D)Animal cells have centrosomes that are involved in this process,but plant cells have microtubular organizing centers that are not detectable during most of the cell cycle.

Question 10

At the end of mitosis,each G₁ daughter cell has

A)twice the DNA and half the cytoplasm of the G₁ parent cell.
B)identical DNA to that of the G₁ parent cell.
C)half the DNA and half the cytoplasm of the G₁ parent cell.
D)twice the cytoplasm and the same amount of DNA as the G₁ parent cell.

Question 11

Some cells have several nuclei per cell.How might such multinucleated cells arise?

A)repeated cytokinesis with no mitosis
B)repeated mitosis with concomitant cytokinesis
C)repeated mitosis without cytokinesis
D)multiple S phases before the entry of a cell into mitosis

Question 12

Scientists isolate cells in various phases of the cell cycle.They find a group of cells that have 1½ times more DNA than G₁ phase cells.The cells of this group are in

A)the process of cytokinesis.
B)the G₂ phase of the cell cycle.
C)M phase.
D)S phase.

Question 13

Figure 11.1
Based on structures present in the figure above,this cell is in which substage of interphase?

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

Question 14

In human and many other eukaryotic species' cells,the nuclear membrane has to disappear in order for what to take place?

A)cytokinesis
B)attachment of mitotic spindle to kinetochores
C)splitting of the centrosomes
D)disassembly of the nucleolus

Question 15

DNA is composed of four nucleosides: adenosine,cytidine,thymidine,and guanosine.If scientists introduced radioactive thymidine into the growth medium of the cells,it would be incorporated into the DNA molecule

A)at any point in the cell cycle.
B)when centromeres split so the two chromosomes can be separated.
C)during DNA replication.
D)as the cell enters G₁ of interphase.

Question 16

One reason cancer cells are easier to culture than normal cells extracted from an organism is that

A)cancer cells do not need to adhere to a substratum to grow.
B)nutrient requirements for cancer cells are precisely defined.
C)cancer cells are better models for demonstrating what happens in an intact organism.
D)cancer cells grow in a more regulated fashion.

Question 17

Which cytoskeletal proteins are important constituents of the contractile structures that form the cleavage furrows involved in animal cell cytokinesis?

A)actin
B)dynein
C)tubulin
D)elastin

Question 18

Myosin is a motor protein involved in animal cell cytokinesis.It binds to ATP or ADP,causing the myosin to move with respect to actin.What is the effect of the interaction between myosin and actin?

A)Vesicles containing plasma membrane constituents are transported to the metaphase plate,where cytokinesis takes place.
B)Excess cytoplasm is removed.
C)The cleavage furrow deepens.
D)It triggers the reformation of the daughter nuclei.

Question 19

The first gap in the cell cycle (G₁)corresponds to

A)normal growth and functioning.
B)the phase in which DNA is being replicated.
C)the beginning of mitosis.
D)the phase between DNA replication and the M phase.

Question 20

Mitosis is the process of chromosome separation.Cytoplasm is divided between the two daughter cells in a process known as

A)karyokinesis.
B)cytokinesis.
C)S phase.
D)G₁ phase.

Question 21

Which of the following statements is FALSE with respect to both bacterial binary fission and eukaryotic mitotic cell division?

A)DNA must be replicated prior to division.
B)Daughter cells must contain the same hereditary material as one another and the parent cell.
C)Cytoplasmic materials must be distributed to each of the daughter cells.
D) The nuclear envelope must disintegrate before the spindle apparatus can move the chromosomes.

Question 22

Which of the following is NOT a result of mitosis?

A)in fungi,haploid spores are produced from a diploid zygote
B)germination of a new plant from a seed
C)asexual reproduction of haploid yeast cells
D)regeneration of a zebrafish fin
E)all of the above are examples where mitosis occurs

Question 23

For cells to divide more rapidly,increased production would likely be required of each of the following proteins EXCEPT

A)p53.
B)cyclins.
C)activated MPF.
D)PDGF.

Question 24

FtsZ is a bacterial cytoskeletal protein.It 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 microtubular organizing center of eukaryotic cells.

Question 25

Another term that could be used to describe the process of binary fission is

A)genetic recombination.
B)fusion.
C)recombination.
D)cloning.

Question 26

Which of the following is not an effect of mitosis-promoting factor (MPF)involved in moving a cell into M phase?

A)phosphorylation of lamins,initiating breakdown of the nuclear membrane
B)phosphorylation of microtubule associated proteins,triggering the formation of the mitotic spindle
C)phosphorylation of an enzyme that breaks down the cyclin molecule
D)degradation of cyclin-dependent kinase

Question 27

At which stage does chromosome organization change from diffuse/uncondensed to a compact/condensed state?

A)Prophase
B)Metaphase
C)Interphase
D)Anaphase
E)Telophase

Question 28

Once researchers understood that chromosomes are moved by the spindle microtubules,the next question they wanted to answer is how the microtubules function to bring about this process.They used fluorescent labels to make the chromosomes and the microtubular structures fluoresce.When anaphase began (centromeres split),they photobleached a section of microtubules.As chromosomes moved toward the poles of the daughter cells,the photobleached sections of the microtubules remained stationary.This result suggests that

A)the microtubules elongate and shorten at the centrosome end.
B)the microtubules overlap and slide with respect to each other,effectively shortening the microtubules without depolymerizing the actual fiber.
C)the microtubules elongate and shorten at their kinetochore end.
D)the microtubules are of constant length;centrosomes move farther apart to separate chromosomes.

Question 29

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.

Question 30

Nerve cells lose their ability to undergo mitosis.Instead,they are permanently stuck in

A)G₀.
B)G₂.
C)S of interphase.
D)meiosis.

Question 31

If a cell has accumulated DNA damage,it is unlikely to

A)pass the G₂ checkpoint.
B)activate DNA repair mechanisms.
C)enter G₁ from mitosis.
D)synthesize cyclin-dependent kinases.

Question 32

Cancer-causing mutated tumour suppressor genes result from which of the following?

A)programmed cell death
B)mutations in genes encoding proteins that normally inhibit progression through the cell cycle
C)mutations that cause overexpression of genes encoding proteins that normally stimulate progression through the cell cycle
D)cell-contact inhibition

Question 33

Which of the following is NOT involved in the regulation of the eukaryotic cell cycle?

A)hormones
B)cyclins
C)cyclin-dependent kinases (CDKs)
D)p53
E)ribosomes

Question 34

Once a cell completes mitosis,molecular division triggers must be turned off.What happens to MPF during mitosis?

A)It is completely degraded.
B)The cyclin-dependent kinases take on a function unrelated to mitosis.
C)Cyclin is degraded;the concentration of cyclin-dependent kinase remains unchanged,but without cyclin,MPF is not formed.
D)Cyclin-dependent kinase is degraded;cyclin concentration remains constant,but without cyclin-dependent kinase,MPF is not formed.

Question 35

The M-phase checkpoint is designed to make sure all chromosomes are attached to the mitotic spindle.If this fails to happen,in which stage of mitosis would the cells be most likely to arrest?

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

Question 36

In the process of chromosome separation,how do microtubules maintain contact with the kinetochores and shorten at the same time?

A)Motor proteins move chromosomes down the microtubular structures of the mitotic spindle.
B)Actin microfilaments cause the microtubular proteins to slide past each other.
C)The centrosomes move apart,so the microtubular proteins do not need to shorten.
D)The centrosomes cause the shortening and depolymerization of the microtubular proteins.

Question 37

Regulatory proteins that serve to prevent a cell from entering the S phase under conditions of DNA damage are also known as

A)cyclins.
B)cyclin-dependent kinases.
C)antibodies.
D)tumor suppressors.

Question 38

What happens when MPF (mitosis-promoting factor)is introduced into immature frog oocytes that are arrested in G₂?

A)Nothing happens.
B)Fertilization occurs.
C)The cells enter mitosis.
D)Cell differentiation is triggered.

Question 39

The term contact inhibition refers to the

A)exchange of signals between cells using cell surface receptions.
B)cessation of cell growth when two cells touch each other.
C)action of non-competitive inhibitors on the catalytic activity of enzymes.