Question 1

Which of the following best describes the role of maturation promoting factor (MPF) in the cell cycle?

Accepted Answer

MPF is a complex of cyclin and cdk that triggers entry into M-phase by phosphorylating target proteins.

Question 2

During the G1/S transition, which molecular event allows the cell to begin DNA replication?

Accepted Answer

Phosphorylation of the Retinoblastoma protein (Rb) by G1 cyclin/cdk releases E2F, enabling S-phase gene expression.

Question 3

A researcher fuses a cell in S-phase with a cell in G1-phase, resulting in the G1 nucleus entering S-phase. What does this experiment demonstrate?

Accepted Answer

S-phase cells contain soluble factors that promote progression into S-phase.

Question 4

Which checkpoint ensures that all chromosomes are properly attached to the mitotic spindle before anaphase begins?

Accepted Answer

Metaphase/Anaphase checkpoint

Question 5

What is the primary function of tumor suppressor genes such as p53 and Rb in the cell cycle?

Accepted Answer

They inhibit cell cycle progression in response to DNA damage or other cellular stress.

Question 6

Which of the following best explains why dysregulation of cell cycle checkpoints can lead to cancer?

Accepted Answer

Checkpoints ensure damaged or unprepared cells do not divide; loss of checkpoint control allows uncontrolled cell proliferation.

Question 7

Which molecular event is required for full activation of the cyclin/cdk complex at the G2/M checkpoint?

Accepted Answer

Addition of two inhibitory phosphate groups and subsequent removal by a phosphatase.

Question 8

A cell is exposed to DNA-damaging agents during S-phase. Which pathway is most likely to be activated to halt cell cycle progression?

Accepted Answer

Activation of checkpoint kinases that phosphorylate p53, leading to expression of cyclin/cdk inhibitors.

Question 9

Which of the following is TRUE regarding the oscillation of mitotic cyclin levels during the cell cycle?

Accepted Answer

Mitotic cyclin levels peak at M-phase entry and are degraded at anaphase.

Question 10

Which signaling pathway is activated by growth factors to initiate the G1/S transition in normal cells?

Accepted Answer

Ras-MAPK pathway

Question 11

What is the consequence of a mutation that causes constitutive activation of Ras in a cell?

Accepted Answer

Uncontrolled cell proliferation due to continuous stimulation of the cell cycle.

Question 12

Which of the following best describes apoptosis?

Accepted Answer

A programmed cell death mechanism activated by checkpoint control or inhibitory signaling.

Question 13

Which Nobel Prize-winning discovery involved the genetic regulation of apoptosis in multicellular organisms?

Accepted Answer

Identification of genes controlling programmed cell death in C. elegans.

Question 14

Which of the following equations correctly represents the phosphorylation reaction catalyzed by a cyclin-dependent kinase (cdk)?

Accepted Answer

$$	ext{Protein} + 	ext{ATP} ightarrow 	ext{Protein-P} + 	ext{ADP}$$

Question 15

A cell fails to degrade mitotic cyclin at anaphase. What is the most likely outcome?

Accepted Answer

The cell will fail to exit mitosis and may not complete cytokinesis.

Question 16

Which of the following is a multi-step process required for activation of the mitotic cyclin/cdk complex?

Accepted Answer

Formation of the complex, addition of inhibitory phosphates, addition of activating phosphate, and removal of inhibitory phosphates.

Question 17

Which phase of the cell cycle is the shortest and consists of prophase, prometaphase, metaphase, anaphase, and telophase?

Accepted Answer

M-phase (mitosis)

Question 18

Which of the following statements about cyclin-dependent kinases (cdks) is CORRECT?

Accepted Answer

Cdks require binding to specific cyclins to become active and regulate cell cycle progression.

Question 19

Which of the following best describes the role of E2F in the cell cycle?

Accepted Answer

E2F is a transcription factor that drives expression of S-phase genes when released from Rb inhibition.

Cell Cycle Regulation, Mitosis, and Apoptosis

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