Question 1

Which phase of the cell cycle is most variable in length among different cell types, and what is the consequence for non-dividing cells?

Accepted Answer

G1 phase; cells can enter the $$G_0$$ state and stop dividing

Question 2

What is the primary function of the M-phase promoting factor (MPF) in the cell cycle?

Accepted Answer

To phosphorylate proteins that start mitosis

Question 3

A scientist injects cytoplasm from an M-phase cell into an interphase cell. What is the expected outcome and what does this demonstrate?

Accepted Answer

The interphase cell will begin M phase, showing that cytoplasmic factors regulate the cell cycle

Question 4

Which of the following best describes the role of cyclin in the activation of MPF?

Accepted Answer

Cyclin binds to Cdk, forming an active complex that phosphorylates target proteins

Question 5

What would happen if a cell failed to degrade cyclin after M phase?

Accepted Answer

MPF would remain active, potentially causing uncontrolled mitosis

Question 6

Which checkpoint ensures that all chromosomes are properly attached to the spindle before sister chromatids separate?

Accepted Answer

Metaphase checkpoint

Question 7

A mutation in the p53 gene is most likely to result in which cellular outcome?

Accepted Answer

Uncontrolled cell division and increased cancer risk

Question 8

Which equation best represents the phosphorylation reaction catalyzed by MPF kinase?

Accepted Answer

$$\mathrm{Protein} + \mathrm{ATP} \rightarrow \mathrm{Protein{-}P} + \mathrm{ADP}$$

Question 9

Why do most animal cells require growth factors in serum to pass the G1 checkpoint?

Accepted Answer

Growth factors activate signaling pathways that promote cell cycle progression

Question 10

Which of the following is a real-world consequence of defective cell-cycle checkpoints?

Accepted Answer

Cells divide uncontrollably, potentially forming tumors

Question 11

A patient is treated with dichloroacetate (DCA) to reactivate mitochondrial activity in cancer cells. What is the intended effect of this treatment?

Accepted Answer

To induce apoptosis in cancer cells

Question 12

Which of the following statements about benign and malignant tumors is correct?

Accepted Answer

Malignant tumors can metastasize and form secondary tumors

Question 13

If a cell passes the G2 checkpoint with unrepaired DNA damage, what is the most likely outcome?

Accepted Answer

The cell may divide with mutations, increasing cancer risk

Question 14

Which protein is most directly responsible for pausing the cell cycle in response to DNA damage?

Accepted Answer

p53

Question 15

What is the role of ubiquitination in the cell cycle?

Accepted Answer

It marks cyclin for degradation, inactivating MPF

Question 16

Which of the following scenarios best illustrates negative feedback in cell-cycle regulation?

Accepted Answer

Active MPF triggers cyclin degradation, reducing MPF activity

Question 17

A cell with defective spindle checkpoint proteins is most likely to:

Accepted Answer

Separate sister chromatids before all are attached to the spindle

Question 18

Which of the following is a direct result of apoptosis in multicellular organisms?

Accepted Answer

Programmed cell death that removes damaged or unnecessary cells

Question 19

Which equation best represents the relationship between cyclin concentration and MPF activity?

Accepted Answer

$$	ext{MPF activity} \propto [	ext{Cyclin}]$$

Question 20

Which of the following best explains why cigarette smoke is linked to lung cancer at the molecular level?

Accepted Answer

It causes mutations in the p53 gene, impairing DNA damage response

The Cell Cycle: Regulation, Control, and Implications for Cell Division

Study Guide - Practice Questions