Examples of Cell Cycle Checkpoint Failure in Cancer

📚 Quick Study Guide

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• Cell Cycle Checkpoints: These are control mechanisms that ensure the fidelity of cell division. Major checkpoints include G1, S, and G2/M.
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• G1 Checkpoint: Determines if the cell should proceed to S phase based on DNA integrity, cell size, and external signals.
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• S Checkpoint: Monitors DNA replication accuracy and arrests the cycle if errors are detected.
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• G2/M Checkpoint: Ensures DNA replication is complete and checks for DNA damage before the cell enters mitosis.
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• Mitotic Spindle Checkpoint: Occurs during metaphase; ensures chromosomes are correctly attached to the spindle fibers.
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• Failure Consequences: When checkpoints fail, cells with damaged DNA can proliferate, leading to genetic instability and cancer development.
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• Key Proteins: Important proteins involved in checkpoints include p53, cyclins, and cyclin-dependent kinases (CDKs).

Practice Quiz

1. Which checkpoint primarily assesses DNA damage before replication?
   1. G2/M Checkpoint
   2. S Checkpoint
   3. G1 Checkpoint
   4. Mitotic Spindle Checkpoint
2. What is the main consequence of cell cycle checkpoint failure?
   1. Controlled cell division
   2. Apoptosis
   3. Uncontrolled cell proliferation
   4. Cellular differentiation
3. Which protein is often referred to as the "guardian of the genome" and plays a crucial role in the G1 checkpoint?
   1. Cyclin B
   2. p53
   3. CDK1
   4. Ras
4. During which phase does the mitotic spindle checkpoint occur?
   1. Prophase
   2. Metaphase
   3. Anaphase
   4. Telophase
5. What is the primary function of the G2/M checkpoint?
   1. To ensure DNA replication is accurate
   2. To ensure DNA replication is complete and DNA damage is repaired
   3. To initiate DNA replication
   4. To promote cellular differentiation
6. Which of the following is NOT a typical factor assessed at the G1 checkpoint?
   1. Cell size
   2. DNA integrity
   3. Spindle fiber attachment
   4. External growth signals
7. What type of protein regulates the cell cycle by phosphorylating target proteins?
   1. Cyclins
   2. Cyclin-dependent kinases (CDKs)
   3. Tumor suppressor proteins
   4. Growth factors