Question 1

Describe the experiment that demonstrated that phosphorylation of nuclear lamins is required for nuclear envelope breakdown during mitosis.

Accepted Answer

Site-directed mutagenesis was used to generate nuclear lamin A that could not be phosphorylated by MPF by converting the serines that are normally phosphorylated to alanines.Expression vectors encoding wild-type or nonphosphorylatable nuclear lamin A were transfected into mammalian cells in culture.In the cells expressing wild-type lamin A,immunofluorescence revealed that lamin A was localized to the nuclear membrane during interphase and then diffusely throughout the cytoplasm during mitosis.Nonphosphorylatable nuclear lamin A remained localized to an intact nuclear envelope,even when cells were in mitosis,as determined by chromosome condensation.

Question 2

Name three activities of G₁ cyclin-CDKs that ensure progression through the cell cycle.

Accepted Answer

G₁ cyclin-CDKs inactivate the APC,activate expression of S phase cyclins,and phosphorylate the S phase inhibitor,which targets it for degradation by the SCF.

Question 3

Which of the following is NOT a way G1/S cyclin/cdks ensure progression through the cell cycle?

Accepted Answer

A) inactivate APC via Cdh1 phosphorylation 
B) phosphorylate the S phase inhibitor (CKI) 
C) activate SCF E3 ligase 
D) activate expression of S-phase cyclins 
A) inactivate APC via Cdh1 phosphorylation 
B) phosphorylate the S phase inhibitor (CKI) 
C) activate SCF E3 ligase 
D) activate expression of S-phase cyclins C

Question 4

All the following statements about destruction of cyclins are true,except:

Accepted Answer

A) Destruction is carried out by proteasomes. 
B) Destruction is preceded by polyubiquitination. 
C) Ubiquitination occurs at specific sites on target molecules. 
D) Ubiquitin targets Cdks. 
A) Destruction is carried out by proteasomes. 
B) Destruction is preceded by polyubiquitination. 
C) Ubiquitination occurs at specific sites on target molecules. 
D) Ubiquitin targets Cdks.

Question 5

During G₁,prereplication complexes:

Accepted Answer

A) are phosphorylated by B-type cyclin-CDKs. 
B) are phosphorylated by DDK. 
C) bind to ORC. 
D) all of the above 
A) are phosphorylated by B-type cyclin-CDKs. 
B) are phosphorylated by DDK. 
C) bind to ORC. 
D) all of the above

Question 6

During which stage of the cell cycle is the chromosome content of a mammalian liver cell 1n?

Accepted Answer

A) G₁ 
B) S 
C) G₂ 
D)  none of the above 
A) G₁ 
B) S 
C) G₂ 
D)  none of the above

Question 7

Separase initiates sister chromatid segregation at anaphase by cleaving:

Accepted Answer

A) APC. 
B) Cdc20. 
C) cyclin B. 
D) Scc1. 
A) APC. 
B) Cdc20. 
C) cyclin B. 
D) Scc1.

Question 8

Failure of which cell-cycle checkpoint is most likely to result in nondysjunction?

Accepted Answer

A) chromosome-segregation checkpoint 
B) DNA-damage checkpoint 
C) unreplicated DNA checkpoint 
D) dysreplicated DNA checkpoint 
A) chromosome-segregation checkpoint 
B) DNA-damage checkpoint 
C) unreplicated DNA checkpoint 
D) dysreplicated DNA checkpoint

Question 9

Which of the following occurs during anaphase A?

Accepted Answer

A) The spindle elongates. 
B) Kinetochores remain attached to shortening kinetochore microtubules. 
C) Chromosomes move to the spindle equator. 
D) The spindle poles move closer together. 
A) The spindle elongates. 
B) Kinetochores remain attached to shortening kinetochore microtubules. 
C) Chromosomes move to the spindle equator. 
D) The spindle poles move closer together.

Question 10

You perform an experiment where you prevent Cdc20 from binding to APC
In a cell line that usually completes the cell cycle in 60 minutes.Your experiment prevents Cdc20 from binding to APC for 120 minutes,and then you fix and stain the DNA,securin,separase and cohesin proteins.Which of the following would NOT be found in the observed cell?

Accepted Answer

A) The cell would contain condensed chromosomes aligned at the metaphase plate. 
B) Cohesins will be localized around the sister chromatids. 
C) Securin would be bound to separase (appear to co-localize). 
D) The DNA will be decondensed because the cell is in interphase. 
A) The cell would contain condensed chromosomes aligned at the metaphase plate. 
B) Cohesins will be localized around the sister chromatids. 
C) Securin would be bound to separase (appear to co-localize). 
D) The DNA will be decondensed because the cell is in interphase.

Question 11

Which of the following is a target of the APC?

Accepted Answer

A) Cdc25 
B) cyclin B 
C) separase 
D) Cdc28 
A) Cdc25 
B) cyclin B 
C) separase 
D) Cdc28

Question 12

What stimulus is required for quiescent cells to re-enter the cell cycle? What events occur after stimulation?

Accepted Answer

Quiescent (G₀)cells re-enter the cell cy

Question 13

Human genes/proteins that regulate the cell cycle are most easily isolated by:

Accepted Answer

A) biochemical purification. 
B) complementation of Xenopus mutants. 
C) complementation of yeast mutants. 
D) positional cloning. 
A) biochemical purification. 
B) complementation of Xenopus mutants. 
C) complementation of yeast mutants. 
D) positional cloning.

Question 14

Investigators found that the cyclin B concentration rises and falls in synchrony with mitotic events and MPF activity.However,correlation is not causality.How did they show that cyclin B was responsible for these cell-cycle events?

Accepted Answer

To show that cyclin B was responsible fo

Question 15

Site-directed mutagenesis of Tyr-15 to Phe in cdc2:

Accepted Answer

A) results in the wee phenotype. 
B) results in a phenotype similar to that caused by mutation in cdc25. 
C) increases the possible number of phosphate groups on Cdc2. 
D) prevents binding of Cdc13. 
A) results in the wee phenotype. 
B) results in a phenotype similar to that caused by mutation in cdc25. 
C) increases the possible number of phosphate groups on Cdc2. 
D) prevents binding of Cdc13.

Question 16

The stable attachment of sister kinetochores to microtubules emanating from opposite spindle poles is called:

Accepted Answer

A) merotelic attachment. 
B) syntelic attachment. 
C) amphitelic attachment. 
D) monotelic attachment. 
A) merotelic attachment. 
B) syntelic attachment. 
C) amphitelic attachment. 
D) monotelic attachment.

Question 17

Chk1is activated by:

Accepted Answer

A) ATR. 
B) Mad1. 
C) p53. 
D) Mad1 and p53. 
A) ATR. 
B) Mad1. 
C) p53. 
D) Mad1 and p53.

Question 18

Breakdown of the nuclear envelope during mitosis is accomplished by CDK-dependent phosphorylation of lamins:

Accepted Answer

A) A and C,but not B. 
B) A and B,but not C. 
C) B and C but not A. 
D) A,B,and C. 
A) A and C,but not B. 
B) A and B,but not C. 
C) B and C but not A. 
D) A,B,and C.

Question 19

Describe how Cdc14 triggers the exit from mitosis in the budding yeast,S.cerevisiae.

Accepted Answer

Cdc14 is a protein phosphatase,which at

Question 20

Which of the following is a substrate of Cln3-Cdc28?

Accepted Answer

A) SBF 
B) SPF 
C) MPF 
D) MBF 
A) SBF 
B) SPF 
C) MPF 
D) MBF

Exam 18: Regulating the Eukaryotic Cell Cycle

Describe the experiment that demonstrated that phosphorylation of nuclear lamins is required for nuclear envelope breakdown during mitosis.

Name three activities of G₁ cyclin-CDKs that ensure progression through the cell cycle.

Which of the following is NOT a way G1/S cyclin/cdks ensure progression through the cell cycle?

All the following statements about destruction of cyclins are true,except:

During G₁,prereplication complexes:

During which stage of the cell cycle is the chromosome content of a mammalian liver cell 1n?

Separase initiates sister chromatid segregation at anaphase by cleaving:

Failure of which cell-cycle checkpoint is most likely to result in nondysjunction?

Which of the following occurs during anaphase A?

Which of the following is a target of the APC?

What stimulus is required for quiescent cells to re-enter the cell cycle? What events occur after stimulation?

Human genes/proteins that regulate the cell cycle are most easily isolated by:

Investigators found that the cyclin B concentration rises and falls in synchrony with mitotic events and MPF activity.However,correlation is not causality.How did they show that cyclin B was responsible for these cell-cycle events?

Site-directed mutagenesis of Tyr-15 to Phe in cdc2:

The stable attachment of sister kinetochores to microtubules emanating from opposite spindle poles is called:

Chk1is activated by:

Breakdown of the nuclear envelope during mitosis is accomplished by CDK-dependent phosphorylation of lamins:

Describe how Cdc14 triggers the exit from mitosis in the budding yeast,S.cerevisiae.

Which of the following is a substrate of Cln3-Cdc28?

Chemical Foundations

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Protein Structure and Function

Culturing and Visualizing Cells

Fundamental Molecular Genetic Mechanisms

Bio-membrane Structure

Genes Genomics and Chromosomes

Transcriptional Control of Gene Expression

Post-Transcriptional Gene Control

Transmembrane Transport of Ions and Small Molecules

Cellular Energetics

Moving Proteins Into Membranes and Organelles

Vesicular Traffic, Secretion, and Endocytosis

Signal Transduction and G-Protein Coupled Receptors

Signaling Pathways That Control Gene Activity

Cell Organization and Movement I: Microfilaments

Cell Organization and Movement II: Microtubules and Intermediate Filaments

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Cell Birth, Lineage, and Death

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