Deck 8: Prb and Control of the Cell Cycle Clock

Question 1

Activation of Myc may result in all of the following EXCEPT

A)Hyperphosphorylation of pRb.
B)Increased expression of CDK4.
C)Degradation of p27^Kip1.
D)Increased transcription of target genes by E2F transcription factors.
E)Decreased activation of cyclin E/CDK2 complexes.

Answer 1

Decreased activation of cyclin E/CDK2 complexes.

Question 2

An increase in cyclin D activity may result from all of the following EXCEPT

A)Activation of the Ras signaling pathway.
B)Activation of the Hedgehog signaling pathway.
C)An increase in NF-κB expression.
D)A decrease in STAT expression.
E)A decrease in p16^INK4A expression.

Answer 2

A decrease in STAT expression.

Question 3

Histone deacetylase HDAC)enzymes

A)Promote initiation of transcription.
B)Complex with hyperphosphorylated pRb.
C)Repress E2F family activity.
D)Add acetyl groups to E2F promoters.
E)Promote initiation of translation.

Answer 3

Repress E2F family activity.

Question 4

When a cell is at G₀,pRb is

A)Undetectable.
B)Unphosphorylated.
C)Hypophosphorylated.
D)Hyperphosphorylated.
E)Overexpressed.

Question 5

pRb in cells undergoing differentiation will generally be

A)Unphosphorylated.
B)Hyperphosphorylated.
C)Bound to E2F transcription factors.
D)Inactivated.
E)Bound to histone acetylases.

Question 6

Which of the following statements is NOT true of the pRb protein?

A)pRb is functionally inactive when it is hyperphosphorylated.
B)pRb is mostly unphosphorylated during the G₀ phase of the cell cycle.
C)pRb is growth-promoting during early G₁ phase.
D)pRb phosphorylation is initiated by D-type cyclins and CDK4/6.
E)pRb is functionally inactivated at the R point.

Question 7

The cyclin/cyclin-dependent kinase pair that is active during the M phase of the cell cycle is

A)Cyclin A/CDC2.
B)Cyclin B/CDC2.
C)Cyclin D/CDK4/6.
D)Cyclin E/CDK2.
E)Cyclin A/CDK2.

Question 8

The resting,nonproliferative phase of the cell cycle is

A)G₀.
B)G₁.
C)G₂.
D)S.
E)M.

Question 9

In a normal cell,signals from the external environment play a role in determining whether the cell will grow or replicate during what phases)of the cell cycle?

A)The S phase only
B)The G₁ phase only
C)The G₂ phase only
D)Both the G₂ and S phases
E)All phases of the cell cycle

Question 10

The critical decision point at which a cell determines its fate at the end of the G₁ phase of the cell cycle is called

A)The transition point.
B)The resolution point.
C)The commitment point.
D)The restriction point.
E)The contraction point.

Question 11

Levels of cyclin A are highest during the phase of the cell cycle in which

A)The cell prepares to enter a quiescent state.
B)Mitosis occurs.
C)The cell is most responsive to mitogenic growth factors.
D)Cytokinesis occurs.
E)DNA replication occurs.

Question 12

Cyclin D/CDK4/6 complexes can be inhibited by

A)p27^Kip1.
B)p15^INK4B.
C)p57^Kip2.
D)p21^Cip1.
E)AP-1.

Question 13

Which of the following may result from activation of TGF-β?

A)Increased activation of cyclin D/CDK4/6 complexes
B)Increased expression of p21^Cip1 in the cytoplasm of the cell
C)Reduced expression of p15^INK4B
D)Decreased activation of cyclin E/CDK2 complexes
E)Phosphorylation of Smad4

Question 14

All of the following are true of the R point EXCEPT

A)It occurs at the G₂/M transition.
B)The cell's fate at this point may be influenced by growth factors in the cell's surroundings.
C)Deregulation of signaling controlling the R point is common in cancer cells.
D)It is followed by the activation of cyclin E/CDK2 complexes.
E)Passage through this point is regulated by phosphorylation of pRb.

Question 15

Which of the following types of mutations would NOT be advantageous to a cancer cell?

A)An inactivating mutation in pRb
B)An inactivating mutation in a gene controlling a DNA damage checkpoint
C)An inactivating mutation in p16^INK4A
D)An inactivating mutation in cyclin D
E)An inactivating mutation in p19^INK4D

Question 16

Which of the following types of mutations are MOST likely to be found in cancer cells?

A)Activating mutations in pRb
B)Mutations resulting in deregulation of the restriction point
C)Mutations resulting in enhanced restriction point regulation
D)Mutations that promote differentiation
E)C and D

Question 17

Which of the following scenarios may contribute to the hyperphosphorylation of pRb?

A)Inactivation of the Ras pathway
B)Inactivation of p21^Cip1
C)Activation of p15^INK4B
D)Inactivation of NF-κB
E)Activation of Smad3/4