DM

Study Guide: Mitosis and Cytokinesis

Overview of Mitosis and Cytokinesis

Cell Cycle Review

  • The cell cycle consists of interphase (G1, S, G2) and the mitotic (M) phase.

  • Mitosis occurs in the M phase and ensures equal distribution of genetic material.

  • Cytokinesis is the final process of cell division, splitting one parent cell into two daughter cells.

Phases of Mitosis

Interphase (Preparation for Mitosis)

  • DNA is in a loosely packed euchromatin state.

  • The cell undergoes normal metabolic functions and prepares for division by replicating DNA during S phase.

  • The nucleus is intact, and the chromosomes are not yet condensed.

Prophase (Chromosome Condensation Begins)

  • Chromatin condenses into visible chromosomes.

  • Sister chromatids (identical copies of a chromosome) are joined at the centromere.

  • The nuclear envelope begins to break down.

  • Mitotic spindle fibers form and attach to centromeres via kinetochores.

Metaphase (Chromosome Alignment)

  • Chromosomes align along the metaphase plate (center of the cell).

  • The spindle checkpoint ensures that each chromatid is properly attached to spindle fibers before proceeding to anaphase.

Anaphase (Chromatid Separation)

  • Sister chromatids separate and are pulled toward opposite poles of the cell.

  • The separated chromatids are now called individual chromosomes.

  • The spindle fibers shorten, ensuring accurate distribution of genetic material.

Telophase (Nuclear Reformation)

  • Chromosomes arrive at opposite poles and begin decondensing back into chromatin.

  • The nuclear envelope re-forms around each set of chromosomes.

  • The mitotic spindle breaks down.

Cytokinesis (Division of the Cytoplasm)

  • Animal cells: A contractile ring of actin filaments forms a cleavage furrow, which pinches the cell into two.

  • Plant cells: A cell plate forms in the center, which develops into a new cell wall.

  • The result is two genetically identical daughter cells, each with the same number of chromosomes as the parent cell.

Key Terms and Definitions

  • Chromatin: Loosely packed DNA found in the nucleus during interphase.

  • Chromosome: Condensed DNA that is visible during mitosis.

  • Sister Chromatids: Identical copies of a chromosome, joined at the centromere.

  • Centromere: Region where sister chromatids are joined.

  • Mitotic Spindle: Microtubule structure that pulls chromatids apart.

  • Metaphase Plate: Imaginary line where chromosomes align during metaphase.

  • Cleavage Furrow: The indentation in an animal cell membrane during cytokinesis.

  • Cell Plate: The structure that forms in plant cells to divide the cytoplasm.