Chapter 11 Mitosis and Cell Cycle

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Mitosis is responsible for what key process in multicellular eukaryotes?

reproduction
growth
wound repair
All of the listed responses are correct.

All of the listed responses are correct.

During what phase of the cell cycle does the DNA become replicated?

M
S
G2
G1

S

What is the difference between a chromatid and a chromosome?

A chromatid always consists of two linear DNA molecules, whereas a chromosome always consists of just one linear DNA molecule.
Chromatids consist of DNA, whereas chromosomes consist of proteins.
A chromatid is one half of a replicated chromosome, whereas a chromosome consists of DNA wrapped around proteins in a highly organized manner.
Chromosomes are always replicated, whereas chromatids are not.

A chromatid is one half of a replicated chromosome, whereas a chromosome consists of DNA wrapped around proteins in a highly organized manner.

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

the parent cell must first replicate its entire genome
the parent cell must first dissolve its nuclear membrane
the parent cell must divide its DNA in half so that each daughter cell gets only the genes it needs
the parent cell must first achieve a specified size

the parent cell must first replicate its entire genome

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:

There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.
Radiolabeled compounds are somewhat cytotoxic, and so cell division was initially inhibited.
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.
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.

There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.

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

in the M phase of the cell cycle
in the G2 phase of the cell cycle
in the S phase of the cell cycle
between the G1 and S phases in the cell cycle

in the S phase of the cell cycle

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

normal growth and cell function
the phase between DNA replication and the M phase
the phase in which DNA is being replicated
the beginning of mitosis

normal growth and cell function

Which statement is correct concerning the relationship between chromosomes and genes, chromatin, or sister chromatids?

Genes are the DNA - protein material that make up entire chromosomes.
Chromatin is a length of DNA in a chromosome that codes for a protein or RNA.
Each replicated chromosome consists of two sister chromatids.
Each unreplicated chromosome consists of two sister chromatids.

Each replicated chromosome consists of two sister chromatids.

For the experiment shown in the figure below, which answer best describes what the outcome would be if microtubules shortened at the opposite end (at or near the spindle pole, not at the kinetochore)?

The darkened section would disappear as soon as chromosomes begin to move.
The darkened section would move closer to the spindle pole but the distance between chromosomes and the darkened section would remain constant.
The darkened section would remain stationary but the distance between chromosomes and the darkened section would shorten.
The darkened section would remain stationary but the distance between chromosomes and the darkened section would increase.

The darkened section would move closer to the spindle pole but the distance between chromosomes and the darkened section would remain constant.

In which mitotic phase are the sister chromatids separated and pulled to opposite poles?

anaphase
telophase
metaphase
prophase

anaphase

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 which of the following?

centrosome
kinetochore
microtubulin
centromere

centrosome

The mitotic spindle is a microtubular structure that is involved in _____.

dissolving the nuclear membrane
splitting of the cell (cytokinesis) following mitosis
separation of sister chromatids
triggering the compaction and condensation of chromosomes

separation of sister chromatids

Some cells have several nuclei per cell. How could such multinucleated cells be explained?

The cell underwent repeated mitosis, but cytokinesis did not occur.
The cell had multiple S phases before it entered mitosis.
The cell underwent repeated cytokinesis but no mitosis.
The cell underwent repeated mitosis with simultaneous cytokinesis.

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

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to _____.

the cleavage furrow of eukaryotic animal cells
the cell plate of eukaryotic plant cells
the mitotic spindle of eukaryotic cells
the microtubule-organizing center of eukaryotic cells

the cleavage furrow of eukaryotic animal cells

For the cell fusion experiment shown in the figure below, what would be the best way to test the hypothesis that the fusion event itself—not something in the cytoplasm—triggered the start of M phase?

Fuse an M-phase cell with an interphase cell.
Give an interphase cell an electric shock.
Fuse two interphase cells.
Inject water instead of cytoplasm into the interphase cell.

Fuse two interphase cells.

Which answer correctly identifies a cell-cycle checkpoint with a criterion for passing it?

G2 checkpoint: Chromosomes have replicated successfully.
G1 checkpoint: Chromosomes have replicated successfully.
S checkpoint: DNA is undamaged.
Metaphase checkpoint: DNA is undamaged.

G2 checkpoint: Chromosomes have replicated successfully.

Proteins that degrade cyclin are activated by events that MPF initiates. Why is this important for cell-cycle regulation?

It sets up an oscillation in cyclin concentration.
It results in the increase in cyclin concentration during interphase.
It causes MPF activity to increase during M phase.
It results in a Cdk concentration that is more or less constant throughout the cell cycle.

It sets up an oscillation in cyclin concentration.

MPF, or mitosis-promoting factor, consists of two important cell cycle regulatory proteins called _____.

tubulin and kinetochorin
actin and myosin
cyclin and cyclin-dependent kinase (CDK)
rubisco and ATP synthase

cyclin and cyclin-dependent kinase (CDK)

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

G0
metaphase
G2
S of interphase

G0

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

The cells enter mitosis.
Cell differentiation is triggered.
Nothing happens.
The cells undergo meiosis.

The cells enter mitosis.

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

Cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed.
It is completely degraded.
It is exported from the cell.
Cyclin-dependent kinase is degraded; cyclin concentration remains constant, but without cyclin-dependent kinase, MPF is not formed.

Cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed.

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

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

degradation of cyclin-dependent kinase

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?

prometaphase
metaphase
telophase
prophase

metaphase

During _____ both the contents of the nucleus and the cytoplasm are divided.

S
mitosis
G1
the mitotic phase
G2

the mitotic phase

During _____ the cell grows and replicates both its organelles and its chromosomes.

interphase
cytokinesis
mitosis
G1
S

interphase

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