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.