$$Cdk_{active} = [Cyclin] \times [Cdk]$$

Question 1

Which of the following best describes the role of p53 in the cell cycle checkpoint response to DNA damage?

Accepted Answer

p53 promotes transcription of a Cdk inhibitor gene, halting cell cycle progression.

Question 2

A mutation that inactivates the EGFR (Epidermal Growth Factor Receptor) would most likely result in which cellular outcome?

Accepted Answer

Failure to progress from G$$_1 to S-$$phase due to lack of external signal.

Question 3

During the G$$_1$$ phase, which regulatory event would prevent progression to S-phase?

Accepted Answer

Transcription of a protein that inhibits Cdk activity.

Question 4

Which of the following is a consequence of a loss-of-function mutation in p53?

Accepted Answer

Cells with DNA damage continue to divide, increasing mutation accumulation.

Question 5

Which step in the hydrophilic signaling pathway is responsible for initiating a cascade of cytoplasmic protein switches?

Accepted Answer

Binding of the ligand to the transmembrane receptor.

Question 6

If a cell has a hyperactive EGFR mutation, what is the most likely effect on the cell cycle?

Accepted Answer

The cell will enter S-phase even without external growth signals.

Question 7

Which of the following equations best represents the relationship between cyclin concentration and Cdk activity?

Accepted Answer

$$Cdk_{active} = [Cyclin] 	imes [Cdk]$$

Question 8

A cell with mutations in both p53 and EGFR is most likely to:

Accepted Answer

Accumulate mutations and divide uncontrollably, forming a genetically diverse tumor.

Question 9

Which checkpoint is primarily responsible for halting the cell cycle in response to DNA damage before mitosis?

Accepted Answer

G$$_2$$ checkpoint

Question 10

What is the main function of Cdk inhibitor proteins in the cell cycle?

Accepted Answer

To prevent activation of cyclin-dependent kinases and halt cell cycle progression.

Question 11

Which of the following scenarios would most likely lead to cancer development?

Accepted Answer

Multiple mutations in checkpoint proteins leading to unregulated cell division.

Question 12

Which process is directly promoted by the activation of EGFR in a target cell?

Accepted Answer

Transcription of G$$_1/S $$cyclin genes.

Question 13

A cell is exposed to a toxin that causes DNA damage. Which molecular event is most likely to occur?

Accepted Answer

Activation of p53 and increased transcription of Cdk inhibitor genes.

Question 14

Which of the following statements about cyclins is correct?

Accepted Answer

Cyclin levels fluctuate during the cell cycle, regulating Cdk activity.

Question 15

If a cell represses transcription of G$$_1$$ cyclin, what is the most likely outcome?

Accepted Answer

The cell will not progress to S-phase.

Question 16

Which of the following best explains why multiple mutations are required for cancer to develop?

Accepted Answer

Redundant checkpoint proteins must be inactivated to allow unregulated division.

Question 17

Which molecular event would NOT occur during the G$$_1$$ phase?

Accepted Answer

Phosphorylation of M-cyclin.

Question 18

A genetically diverse tumor is difficult to treat because:

Accepted Answer

Different tumor cells may respond differently to therapies due to distinct mutations.

Question 19

Which of the following is a direct result of p53 activation after DNA damage?

Accepted Answer

Transcription of p21, a Cdk inhibitor.

Question 20

Which equation best describes the effect of a Cdk inhibitor on Cdk activity?

Accepted Answer

$$Cdk_{active} = [Cdk] - [Cdk\_inhibitor]$$

Regulation of the Cell Cycle: Cyclins, CDKs, and Checkpoints

Study Guide - Practice Questions