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Exam 18: The Cell-Division Cycle

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Question 21

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Which of the following statements is TRUE?

A) Anaphase A must be completed before anaphase B can take place.
B) In cells in which anaphase B predominates, the spindle will elongate much less than in cells in which anaphase A dominates.
C) In anaphase A, both kinetochore and interpolar microtubules shorten.
D) In anaphase B, microtubules associated with the cell cortex shorten.

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Question 22

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Before chromosomes segregate in M phase, they and the segregation machinery must be appropriately prepared.Indicate whether the following statements are TRUE or FALSE.If false, change a single noun to make the statement true.

Premises

Responses

The centromere nucleates a radial array of microtubules called an aster, and its duplication is triggered by S-Cdk.

True

Each centrosome contains a pair of centrioles and hundreds of $\mathrm{Y}$ -tubulin rings that nucleate the growth of microtubules.

False

Cohesins are required to make the chromosomes more compact and thus to prevent tangling between different chromosomes.
A)open-ended question

Sister chromatids are held together by condensins from the time they arise by DNA replication until the time they separate at anaphase.

Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis.

Premises

The centromere nucleates a radial array of microtubules called an aster, and its duplication is triggered by S-Cdk.

Each centrosome contains a pair of centrioles and hundreds of $\mathrm{Y}$ -tubulin rings that nucleate the growth of microtubules.

Cohesins are required to make the chromosomes more compact and thus to prevent tangling between different chromosomes.
A)open-ended question

Sister chromatids are held together by condensins from the time they arise by DNA replication until the time they separate at anaphase.

Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis.

Responses

True

False

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Correct Answer

Premises

Responses

The centromere nucleates a radial array of microtubules called an aster, and its duplication is triggered by S-Cdk.

Each centrosome contains a pair of centrioles and hundreds of $\mathrm{Y}$ -tubulin rings that nucleate the growth of microtubules.

Cohesins are required to make the chromosomes more compact and thus to prevent tangling between different chromosomes.
A)open-ended question

Sister chromatids are held together by condensins from the time they arise by DNA replication until the time they separate at anaphase.

Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis.

Premises

The centromere nucleates a radial array of microtubules called an aster, and its duplication is triggered by S-Cdk.

Each centrosome contains a pair of centrioles and hundreds of $\mathrm{Y}$ -tubulin rings that nucleate the growth of microtubules.

Cohesins are required to make the chromosomes more compact and thus to prevent tangling between different chromosomes.
A)open-ended question

Sister chromatids are held together by condensins from the time they arise by DNA replication until the time they separate at anaphase.

Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis.

Responses

Question 23

Multiple Choice

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A mutant yeast strain stops proliferating when shifted from 25°C to 37°C.When these cells are analyzed at the two different temperatures, using a machine that sorts cells according to the amount of DNA they contain, the graphs in Figure 18-2 are obtained. Figure 18-2 Which of the following would NOT explain the results with the mutant?

Consider an animal cell that has eight chromosomes (four pairs of homologous chromosomes) in G₁ phase.How many of each of the following structures will the cell have at mitotic prophase? A.sister chromatids B.centromeres C.kinetochores D.centrosomes E.centrioles

Which stage of mitosis in an animal cell does each part of Figure 18-9 represent? Figure 18-9

Levels of Cdk activity change during the cell cycle, in part because

Which of the following statements is FALSE?

Which of the following precede the re-formation of the nuclear envelope during M phase in animal cells?

You engineer yeast cells that express the M cyclin during S phase by replacing the gene regulatory sequences of the M cyclin gene with those of the S cyclin gene.Keeping in mind that yeast cells have one common Cdk that binds to all cyclins, which of the following outcomes is LEAST likely during this experiment?

Before a cell can enter M phase, two structures from Figure 18-12 must be duplicated.Write the letters corresponding to the lines pointing to these structures, and write the names of the structures next to the letters. Figure 18-12

Which of the following statements about the cell cycle is FALSE?

What is the cause of the massive amount of programmed cell death of nerve cells (neurons) that occurs in the developing vertebrate nervous system, and what purpose does it serve?

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once. $\begin{array}{lll}\text { anaphase } & \text { differentiation } & \text { myostatin } \\\text { annihilation } & \mathrm{G}_{0} & \text { nourishment } \\\text { arrestase } & \mathrm{G}_{1} & \text { nutrition } \\\text { Bcl2 } & \mathrm{G}_{2} & \text { phosphatases } \\\text { biosynthetic } & \text { growth factors } & \text { proliferation } \\\text { cyclin } & \text { interphase } & \text { receptor } \\\text { cascades } & \text { ligand } & \mathrm{S} \\\text { caspase } & \mathrm{M} & \text { survival factors } \\\text { Cdk } & \text { mitogens } & \text { transcription }\end{array}$ The survival, __________, and size of each cell in an animal are controlled by extracellular signal molecules secreted by neighboring and distant cells.Many of these signal molecules bind to a cell-surface __________ and trigger various intracellular signaling pathways.One class of signal molecules, called __________, stimulates cell division by releasing the molecular brakes that keep cells in the __________or __________ phase of the cell cycle.Members of a second class of signal molecules are called __________, because they stimulate cell growth and an increase in cell mass.The third class of signal molecules, called __________, inhibits apoptosis by regulating members of the __________ family of proteins.In addition to such stimulatory factors, some signal proteins, such as __________ act negatively on other cells, inhibiting their survival, growth, or proliferation.

A cell with nuclear lamins that cannot be phosphorylated in M phase will be unable to

Which organelle fragments during mitosis?

Which of the following statements about kinetochores is TRUE?

Which of the following does not occur during M phase in animal cells?

Apoptosis differs from necrosis in that necrosis

A friend declares that chromosomes are held at the metaphase plate by microtubules that push on each chromosome from opposite sides.Which of the following observations does not support your belief that the microtubules are pulling on the chromosomes?

The Retinoblastoma (Rb) protein blocks cells from entering the cell cycle by