Cell Biology Exam Review

Characteristics of Living Organisms

• Contain a genetic program

• Grow and reproduce

• Harvest, transform, and use energy and chemical building blocks

• Respond to their surroundings

• Regulate their internal environment

• Consist of one or more cells

Cell Division

• Cells divide to:

  • Create new organisms

  • Allow an organism to grow

  • Maintain an organism (replacement and repair)

  • During embryonic development

Mitotic vs. Meiotic Cell Division

• Mitotic cell division → two genetically identical daughter cells.

• Meiotic cell division → four genetically different daughter cells.

The Cell Cycle

• The cell cycle includes:

  • Interphase

    • G_1 phase (preparation for DNA synthesis)

    • S phase (DNA synthesis)

    • G_2 phase (preparation for mitosis and cytokinesis)

    • G_0 phase (cells that are not actively dividing)

  • M phase (mitosis and cytokinesis)

Phases of the Cell Cycle Explained

• Interphase: Period between M phases.

• M Phase: Mitotic phase when a cell divides; consists of mitosis (division of chromosomes) and cytokinesis (division of cytoplasm).

• G_1 Phase: "Growth" or "Gap" phase; cell prepares to divide.

• G0 Phase: Cells in G0 do not divide.

Stages of Mitosis

• Interphase:

  • Chromosomes are duplicated but uncondensed.

  • Centrosomes with centriole pairs are present.

  • Nuclear envelope is intact.

  • Nucleolus is visible.

• Prophase:

  • Early mitotic spindle forms.

  • Chromosomes condense and become discernable.

• Prometaphase:

  • Nuclear envelope fragments.

  • Kinetochore microtubules attach to kinetochores of sister chromatids.

  • Nonkinetochore microtubules interact.

• Metaphase:

  • Chromosomes are lined up at the metaphase plate (equator).

  • Sister chromatids are attached to kinetochore microtubules from opposite poles.

• Anaphase:

  • Sister chromatids are pulled apart to opposite poles of the cell.

  • Daughter chromosomes move toward the poles.

• Telophase and Cytokinesis:

  • Sister chromatids are at opposite poles of the cell.

  • Cytokinesis begins.

  • Cleavage furrow forms.

  • Nuclear envelope reforms.

  • Nucleolus reforms.

Review of Cell Division Concepts

• Reasons cells divide.

• Comparison of outcomes of mitotic and meiotic cell division.

• Description of what happens during the cycle in:

  • G1, S, G2 (and G_0) of interphase

  • Mitosis and cytokinesis of M phase

• Mitosis is not a synonym for M phase. M phase includes both mitosis and cytokinesis.