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Understanding the Cell Cycle and Mitosis

May 5, 2025

Lecture Notes: The Cell Cycle and Mitosis

Introduction

  • Commonality between a baby and mold: Both have cells that undergo the cell cycle, progressing through mitosis to grow and survive.
  • Importance of the topic: Understanding the cell cycle and mitosis is crucial for the AP Biology test.
  • Outline:
    1. Overview of the cell cycle
    2. Cell division: Binary fission, mitosis, and meiosis
    3. Cell cycle checkpoints
    4. Stages of mitosis

The Cell Cycle

  • Definition: Sequence of growth (interphase) and division (mitosis) in a cell.
  • Parts of the Cell Cycle:
    • Interphase:
      • G1 Phase: Cell metabolizes energy, creates proteins and lipids, grows.
      • S Phase (Synthesis): DNA replication occurs via DNA polymerase.
      • G2 Phase: Cell grows further, replicates organelles.
    • G0 Phase (Quiescence): Non-dividing state; e.g., nerve cells.
    • Mitosis: Separation of DNA into two new daughter cells.

Types of Cell Division

  • Binary Fission:
    • Used by bacteria and single-celled organisms.
    • Simpler due to single circular DNA.
  • Mitosis:
    • Complex, involves separation of duplicated chromosomes.
    • Used by single-celled eukaryotes for reproduction, and multicellular organisms for growth.
  • Meiosis:
    • Used in sexually reproducing organisms to form gametes with half the DNA.

Cell Cycle Checkpoints

  • G1 Checkpoint:
    • Ensures cell size, nutrient availability, DNA integrity.
    • Failure leads to G0 phase.
  • G2 Checkpoint:
    • Ensures completion of DNA replication, checks for DNA damage.
    • Failure leads to apoptosis.
  • Metaphase Checkpoint (M Checkpoint):
    • Ensures equal chromosome separation.
    • Failure can lead to uncontrolled cell division (cancer).

Stages of Mitosis

  1. Prophase:
    • Chromosomes duplicated; centrosomes migrate; nuclear envelope breaks down.
  2. Metaphase:
    • Chromosomes line up on metaphase plate.
  3. Anaphase:
    • Sister chromatids separate, pulled to opposite poles.
  4. Telophase:
    • Nuclear envelope reforms; cleavage furrow forms.
  5. Cytokinesis:
    • Complete separation of daughter cells.

Conclusion

  • Review and Practice:
    • Use quizzes and resources to test understanding.
    • Review checkpoints and phases for AP style questions.

Resources: Subscribe to the Biology Dictionary YouTube for more videos and resources.

Note: This summary is based on a lecture for Section 4.6 of the AP Biology curriculum.

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