4.7 Warm-up

What is the role of protein kinases?

• remove phosphate groups to deactivate enzymes

• trigger apoptosis

• add phosphate groups and energy to activate enzymes

• stop the cell cycle

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4.7

Which of these may be assessed by various proteins during a "checkpoint"? CHECK ALL THAT APPLY

• Ensure that all chromosomes have lined up in the center of the cell before sister chromatids separate

• Ensure that spindle fibers have attached to all centromeres before cell division

• Ensure that DNA has been replicated properly

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4.7

Which description is true about cell cycle regulation?

• Changing concentrations of Cdk result in binding to cyclin
• Changing concentrations of cyclin result in binding to Cdk
• MPF complex formation decreases with increased Cdk levels
• MPF complex formation decreases with increased cyclin levels

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4.7

In which stage of the cell cycle are cells most susceptible (likely to experience) to mutations?

• G1

• S

• G2

• G0

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4.7

Which of the following correctly describes cells that are in the G₀ phase?

• Mature nerve and muscle cells are unable to divide and are permanently in G₀.

• Many cells enter G₀ when they reach the checkpoint during the M phase.

• Cells in G₀ are growing and preparing for cell division.

• DNA replication occurs during G₀.

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4.7

How does the concentration of cyclin dependent kinases (Cdk) change as the cell proceeds through the cell cycle?

• Cdk concentration remains constant.
• Cdk concentration increases during interphase and decreases during mitosis.
• Cdk concentration decreases during interphase and increases during mitosis.
• Cdk concentration correlates directly with MPF concentration.

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4.7

The normal function of a tumor suppressor gene is 

• to produce growth signals
• to code for proteins that inhibit, or slow, cell division
• to cause the cell to move faster through the cell cycle
• to attack cancer cells in the body

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4.7

Which of these is a risk factor for developing cancer? CHECK ALL THAT APPLY

• growing older

• genetic inheritance

• exposure to carcinogens (toxins that can damage DNA)

• smoking

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4.7

Most cells that have become transformed into cancer cells have which of the following characteristics when compared to normal, healthy cells?

• Shorter cell cycle

• More carefully regulated rates of cell division

• Lower rates of mitosis

• Higher rates of protein translation

• Identical DNA

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4.7

Cancer can result from a variety of different mutational events. Which of the following is LEAST likely to result in the initiation of a cancerous tumor?

• A receptor mutation results in activation of a cell-division pathway in the absence of the appropriate ligand.

• A mutation results in the loss of the ability to produce a tumor-suppressor protein.

• A defect in a cell-cycle checkpoint prevents a cell from entering the S phase.

• At the anaphase checkpoint, separation of chromatids occurs without all centromeres being attached to kinetochore microtubules from both poles.

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4.7