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BIOL 3040: Cell Structure and Function > Exam 3: Ch 17 CLICKER > Flashcards

Exam 3: Ch 17 CLICKER Flashcards

1
Q

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 below are obtained.
Which of the following would not explain the results with the mutant?

(a) inability to initiate DNA replication

(b) inability to begin M phase

(c) inability to activate proteins needed to enter S phase

(d) inappropriate production of a signal that causes the cells to remain in G1

A

(b) inability to begin M phase

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2
Q

Which of the following events does not usually occur during interphase?

A- Cells grow in size.
B- The nuclear envelope breaks down.
C- DNA is replicated.

A

B- The nuclear envelope breaks down.

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3
Q

Progression through the cell cycle requires a cyclin to bind to a Cdk because _________.

A- the cyclins are the molecules with the enzymatic activity in the complex.

B- the binding of a cyclin to Cdk is required for Cdk enzymatic activity.

C- cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle.

A

B- the binding of a cyclin to Cdk is required for Cdk enzymatic activity.

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4
Q

Substrate specificity is highly dependent on which of these subunits of PP2A phosphatase?

A- scaffold subunit
B- regulatory subunit
C- catalytic subunit

A

B- regulatory subunit

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5
Q

Which statement is FALSE?

A- Cdc25 activity is further stimulated by M-CDK phosphorylation, which creates a positive feedback for M-CDK activity.

B- Wee1 activity is inhibited by M-CDK phosphorylation, which creates a positive feedback for M-CDK activity.

C- Activation of M-CDK activates PP2A-B55.

A

C- Activation of M-CDK activates PP2A-B55.

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6
Q

Which complex of APC/C is active in early G1?

A. APC/C-Cdc20
B. APC/C-Cdh1

A

B. APC/C-Cdh1

Cdh1 is phosphorylated by Cdks and kept inactive from late G1 till anaphase.

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7
Q

Activation of APC/C is important for:

A. Metaphase to Anaphase transition
B. Entry into Prophase
C. G2 to M transition

A

A. Metaphase to Anaphase transition

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8
Q

Activation of which of these factors inhibit MCM2 loading onto DNA?

A- Cdt1
B- Cdc6
C- ORC
D- S-Cdk

A

D- S-Cdk

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9
Q

At the end of DNA replication, the sister chromatids are held together by the ______

A- kinetochores.
B- securins.
C- cohesins.
D- histones.

A

C- cohesins.

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10
Q

he concentration of mitotic cyclin (M cyclin) ________________.

A- remains constant throughout cell cycle.

B- falls toward the end of M phase as a result of ubiquitylation and degradation.

C- is highest in G1 phase

A

B- falls toward the end of M phase as a result of ubiquitylation and degradation.

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11
Q

Consider the centrosome duplication cycle and in relation to replication, is centrosome
duplication:

A- Conservative
B- Semi-conservative

A

B- Semi-conservative

Centrosome duplication is semiconservative. The paired centrioles in the centrosome
separate, and each serves to nucleate the assembly of a new centriole. As a
consequence, each new centrosome consists of one old and one new centriole. Thus, centrosome duplication is analogous to DNA replication, in which the new double helix consists of one old DNA strand and one newly replicated DNA strand

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12
Q

For microtubule (spindle) organization in mitosis, chromosomes are not as important as centrosomes.

A- True
B- False

A

B- False

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13
Q

Separase is kept inactive due to:

A- Activation of APC/C-Cdc20
B- Binding of securin
C- Degradation of securin

A

B- Binding of securin

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14
Q

Actin and myosin filaments are also main components of the mitotic spindle.

A- True
B- False

A

B- False

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15
Q

Contractile ring is pinched by a process called abscission to complete cytokinesis.

A- True
B- False

A

B- False

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16
Q

If RhoA is not activated at the cortex in the equator between spindle poles, then ___________________.

A- contraction of the actin-myosin ring is inhibited

B- centralspindlin is not assembled at the spindle midzone

C- Aurora B kinase does not activate centralspindlin

A

A- contraction of the actin-myosin ring is inhibited

17
Q

Which of these inhibit M-Cdk activity in anaphase?

A- activation of APC/C- Cdc20
B- activation of S-Cyclin
C- inhibition of APC/C activity

A

A- activation of APC/C- Cdc20

18
Q

Which of these is a CDK inhibitor, whose transcription is induced by p53?

A- Mdm2
B- p21
C- Rb

A

B- p21

19
Q

If T-loop is in active site, then CDK is:

A- Active
B- Inactive

A

B- Inactive

20
Q

CDK alone is:

A- Active
B- Inactive

A

B- Inactive

21
Q

Cdk/Cyclin bound to p27 or p21 is:

A- Active
B- Inactive

A

B- Inactive

22
Q

Which one of the following statements accurately describes how Greatwall and Ensa collaborate to turn off PP2A-B55?

A. Greatwall inactivates Ensa, an activator of PP2A-B55, turning PP2A-B55 off.

B. Greatwall and Ensa form a complex, which binds to PP2A-B55, turning it off.

C. Greatwall phosphorylates Ensa, which then binds to PP2A-B55, turning it off.

D. Ensa activates Greatwall, which adds a phosphate to PP2A-B55, turning it off.

A

C. Greatwall phosphorylates Ensa, which then binds to PP2A-B55, turning it off.

23
Q

Which one of the following possibilities would give the most rapid activation of M-Cdk?

A. M-Cdk phosphorylates Wee1 and Cdc25, inactivating Wee1 and inactivating Cdc25.

B. M-Cdk phosphorylates Wee1 and Cdc25, inactivating Wee1 and activating Cdc25.

C. M-Cdk phosphorylates Wee1 and Cdc25, activating Wee1 and activating Cdc25.

D. M-Cdk phosphorylates Wee1 and Cdc25, activating Wee1 and inactivating Cdc25.

A

B. M-Cdk phosphorylates Wee1 and Cdc25, inactivating Wee1 and activating Cdc25.

24
Q

G1-Cdk promotes synthesis of which of the following cyclins?

A. G1/S-cyclin and S-cyclin
B. G1/S-cyclin only
C. S-cyclin only
D. G1/S-cyclin and M-cyclin

A

A. G1/S-cyclin and S-cyclin

25
Q

Entry into mitosis signals an abrupt change in the cell’s microtubules. During
prophase, and particularly in prometaphase and metaphase, the average
lifetime of a microtubule increases dramatically, giving rise to the stable
metaphase spindle that is so prominent in the microscope.

A. True
B. False

A

B. False

Entry into mitosis signals an abrupt change in the cell’s microtubules. During prophase, and particularly in prometaphase and metaphase, the average lifetime of a
microtubule decreases dramatically—particularly the lifetime of non-kinetochore microtubules, which exist for only 15 to 30 seconds. This increase in microtubule instability, coupled with the increased ability of the spindle to nucleate microtubules, results in a remarkably dense and dynamic array of spindle microtubules. Microtubules outside the spindle typically have a lifetime measured in minutes.

26
Q

You have obtained an antibody to myosin that prevents the movement of myosin
molecules along actin filaments. If this antibody were injected into cells, would you
expect the movement of chromosomes at anaphase to be affected? How would you
expect antibody injection to affect cytokinesis?

A. Chromosome movement would be inhibited; cytokinesis would be unaffected.

B. Chromosome movement would be unaffected; cytokinesis would be inhibited.

C. Chromosome movement would be inhibited; cytokinesis would be inhibited.

D. Chromosome movement would be unaffected; cytokinesis would be unaffected.

A

B. Chromosome movement would be unaffected; cytokinesis would be inhibited.

27
Q

Chromosomes are pulled to the spindle pole at anaphase like fish being reeled in on a line.

A. True
B. False

A

B. False

28
Q

Which of these factors are important to ensure that the Mcm helicases are loaded onto origins of replication in G1 phase?

A- Cdt1
B- ORC
C- Cdc6
D- All of the above
E- None of the above

A

D- All of the above

29
Q

What is the term for the stage of mitosis in which the spindle poles move apart?

A. Cytokinesis
B. Anaphase A
C. Metaphase
D. Anaphase B

A

D. Anaphase B

30
Q

Microtubule flux is a type of force that pulls:

A. Kinetochore microtubules to the spindle equator due to plus end depolymerization.

B. Kinetochore microtubules to the spindle poles due to minus end depolymerization.

C. Chromosome arms to the spindle equator due to the movement of the chromokinesin
motor proteins.

A

B. Kinetochore microtubules to the spindle poles due to minus end depolymerization.

31
Q

Which statement is TRUE?

A- When Cdt1 levels are low in G1, Geminin levels are high.

B- When Geminin levels are low in G2, Cdt1 levels are high.

C- Degradation of Geminin by APC/C in G1, keeps Cdt1 active

A

C- Degradation of Geminin by APC/C in G1, keeps Cdt1 active

BIOL 3040: Cell Structure and Function (49 decks)

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