$$\text{Protein} + \text{ATP} \xrightarrow{\text{Kinase}} \text{Phosphorylated Protein} + \text{ADP}$$

Question 1

Which of the following best describes the role of the G1 checkpoint in the cell cycle?

Accepted Answer

It checks for DNA damage and determines whether the cell will proceed to DNA synthesis or enter a non-dividing state.

Question 2

A cell receives a stop signal at the M phase checkpoint. What is the most likely consequence?

Accepted Answer

The cell will not proceed to anaphase until all chromosomes are properly attached to the spindle.

Question 3

Which molecular complex triggers the cell’s passage through the G2 checkpoint into mitosis?

Accepted Answer

Maturation Promoting Factor (MPF), a cyclin-Cdk complex

Question 4

What is the effect of phosphorylation on protein activity in the cell cycle?

Accepted Answer

Phosphorylation can either activate or inactivate proteins, depending on the context.

Question 5

Cancer cells differ from normal cells in culture because they:

Accepted Answer

Continue to divide even when not attached to a substrate and when crowded.

Question 6

Which equation best represents the phosphorylation of a protein by a kinase?

Accepted Answer

$$	ext{Protein} + 	ext{ATP} \xrightarrow{	ext{Kinase}} 	ext{Phosphorylated Protein} + 	ext{ADP}$$

Question 7

A cell in the G0 phase can re-enter the cell cycle in response to:

Accepted Answer

External cues such as growth factors released during injury.

Question 8

Which of the following is a direct consequence of nondisjunction during mitosis?

Accepted Answer

Cells with abnormal chromosome numbers are produced.

Question 9

What is the primary function of the cell cycle control system?

Accepted Answer

To trigger and coordinate key events in the cell cycle through molecular signals.

Question 10

Which of the following best explains why cancer cells can form tumors?

Accepted Answer

They lose cell cycle controls and continue to divide even when crowded and unattached.

Question 11

During which phase of the cell cycle does DNA synthesis occur?

Accepted Answer

S phase

Question 12

Which of the following is NOT a characteristic of malignant tumor cells?

Accepted Answer

Density-dependent inhibition

Question 13

A scientist adds platelet-derived growth factor (PDGF) to a culture of human fibroblasts. What is the expected outcome?

Accepted Answer

The fibroblasts will proliferate in response to PDGF.

Question 14

Which of the following statements about MPF (Maturation Promoting Factor) is correct?

Accepted Answer

MPF triggers the cell past the G2 checkpoint into the M phase.

Question 15

Which of the following is a real-world consequence of loss of cell cycle control in cancer cells?

Accepted Answer

Formation of malignant tumors that can invade tissues and metastasize

Question 16

Which of the following best describes density-dependent inhibition?

Accepted Answer

Cells stop dividing when they become crowded.

Question 17

Which of the following treatments targets rapidly dividing cells by interfering with specific stages of the cell cycle?

Accepted Answer

Chemotherapy

Question 18

If a cell fails to receive a go-ahead signal at the G1 checkpoint, what is the most likely outcome?

Accepted Answer

The cell will exit the cell cycle and enter the G0 phase.

Question 19

Which of the following is a function of cyclin-dependent kinases (Cdks) in the cell cycle?

Accepted Answer

Cdks are active only when bound to cyclins and regulate cell cycle transitions.

Question 20

Which of the following best explains why normal mammalian cells form a single layer in culture?

Accepted Answer

They exhibit both anchorage dependence and density-dependent inhibition.

Cell Cycle Regulation and Cancer: Control Mechanisms and Loss of Regulation

Study Guide - Practice Questions