Question 1

Which of the following best describes the main difference between mitosis and meiosis in eukaryotic cells?

Accepted Answer

Mitosis produces genetically identical daughter cells, while meiosis produces genetically diverse gametes.

Question 2

During which phase of the cell cycle does DNA replication occur, and what experimental evidence supports this?

Accepted Answer

S phase; autoradiography with radioactively labeled nucleotides showed DNA synthesis during interphase.

Question 3

Which of the following events occurs during prometaphase of mitosis?

Accepted Answer

The nuclear envelope breaks down and spindle fibers attach to kinetochores.

Question 4

What is the primary function of the G1 phase in the eukaryotic cell cycle?

Accepted Answer

To allow the cell to grow and generate enough organelles for normal daughter cell function.

Question 5

Which protein complex is responsible for triggering the onset of mitosis, and how is its activity regulated?

Accepted Answer

MPF (M phase-promoting factor); its activity depends on cyclin binding to Cdk and is regulated by cyclin concentration.

Question 6

A researcher observes that a cell fails to divide after DNA replication, and the cell accumulates DNA damage. Which checkpoint is most likely malfunctioning?

Accepted Answer

G1 checkpoint, because it prevents cells with damaged DNA from proceeding to S phase.

Question 7

Which of the following best explains how microtubules contribute to chromosome movement during anaphase?

Accepted Answer

Microtubules depolymerize at the kinetochore end, pulling chromatids toward the spindle poles.

Question 8

In animal cells, cytokinesis is accomplished by which of the following mechanisms?

Accepted Answer

Formation and contraction of a cleavage furrow composed of actin and myosin microfilaments.

Question 9

Which of the following scenarios would most likely result in the development of cancer?

Accepted Answer

A mutation that inactivates a tumor suppressor gene such as p53.

Question 10

A scientist fuses a cell in M phase with a cell in G1 phase. What is the most likely outcome, and what does this demonstrate about cell cycle regulation?

Accepted Answer

The G1 nucleus begins to enter M phase, demonstrating the presence of a cytoplasmic factor that induces mitosis.

Question 11

Which of the following best describes the role of growth factors in the regulation of the cell cycle in multicellular eukaryotes?

Accepted Answer

Growth factors act as social signals that increase cyclin expression, allowing cells to pass the G1 checkpoint.

Question 12

Which of the following is a key difference between cytokinesis in plant and animal cells?

Accepted Answer

Plant cells form a cell plate from Golgi-derived vesicles, while animal cells form a cleavage furrow from actin and myosin.

Question 13

A mutation causes the overproduction of G1 cyclin in a cell. What is the most likely consequence?

Accepted Answer

The cell will pass the G1 checkpoint too frequently, leading to uncontrolled cell division.

Question 14

Which of the following best explains why cancer is considered a family of diseases rather than a single disease?

Accepted Answer

Cancer can result from a variety of molecular defects affecting cell-cycle control, leading to diverse types and behaviors.

Question 15

Which of the following statements about the role of the Rb protein in the cell cycle is correct?

Accepted Answer

Rb binds to E2F, keeping it inactive until growth factors signal the cell to proceed through G1.

Question 16

Which of the following best describes the process of binary fission in prokaryotes compared to cytokinesis in eukaryotes?

Accepted Answer

Binary fission is similar to animal cytokinesis, involving the division of the cytoplasm after DNA replication.

Question 17

A cell is observed to have condensed chromosomes, a broken-down nuclear envelope, and spindle fibers attached to kinetochores. In which phase of mitosis is this cell most likely found?

Accepted Answer

Prometaphase

Question 18

Which of the following equations best represents the relationship between cyclin concentration and MPF activity during the cell cycle?

Accepted Answer

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

Question 19

Which checkpoint ensures that all chromosomes are properly attached to the spindle before the cell proceeds with division?

Accepted Answer

Metaphase (M-phase) checkpoint

Question 20

A patient is diagnosed with a malignant tumor. Which of the following characteristics would you expect to observe in the cancer cells?

Accepted Answer

The cells invade other tissues and can metastasize via blood or lymph vessels.

The Cell Cycle: Structure, Regulation, and Cancer

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