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Lesson 4: Mitosis

  • Aim: What is Mitosis?

  • Terminology:

    • Extracellular space

    • Protein channel

    • Cell membrane

    • Carrier proteins

    • Intracellular space

Steps of the Cell Cycle

  • 3 Stages of Cell Cycle:

    1. Interphase

    2. Mitosis (M Phase)

    3. Cytokinesis

  • Interphase Components:

    • Growth 1

    • DNA Synthesis (S phase)

    • Growth 2

  • Mitosis Stages:

    • Prophase

    • Metaphase

    • Anaphase

    • Telophase

Interphase

  • 3 Stages:

    1. Growth 1 (G1)

      • Cell grows and produces more VIP molecules (nucleotides, enzymes, etc.)

    2. DNA Synthesis (S)

      • DNA replication occurs

    3. Growth 2 (G2)

      • Continued growth and preparation for cell division

Mitosis

Prophase

  • Checklist:

    • Chromatin condenses

    • Nucleoli disappear

    • Duplicated chromosomes appear as sister chromatids

    • Mitotic spindle formation begins

    • Centrosomes move apart

Prometaphase

  • Checklist:

    • Nuclear envelope fragments

    • Microtubules enter nuclear area; some attach to kinetochores

Metaphase

  • Checklist:

    • Centrosomes at opposite poles

    • Chromosomes align at metaphase plate

    • Microtubules attach to each kinetochore

Anaphase

  • Checklist:

    • Sister chromatids separate and move to opposite poles

    • Cell elongation occurs due to shortening of microtubules

Telophase

  • Checklist:

    • Two daughter nuclei form

    • Nucleoli reappear

    • Chromosomes become less condensed

  • Cytokinesis Checklist:

    • Cytokinesis occurs

    • Animals: cleavage furrow forms from contractile ring of actin filaments

    • Plants: vesicles from Golgi form a cell plate

Detailed Mitosis Steps

Prophase

  • Nucleus dissolves

  • DNA condenses: chromosomes visible

  • Spindle fibers form

Metaphase

  • Spindle fibers attach to chromosomes

  • Chromosomes line up on the equatorial plate

Anaphase

  • Contract spindle fibers to move chromatids to opposite poles

Telophase

  • Nucleus reforms

  • DNA decondenses

  • Cell membrane begins to pinch in

Cytokinesis

  • Cytoplasm divides

  • Formation of 2 genetically identical daughter cells

Tracking Chromosomes

  • Maternal and Paternal chromosomes observed

  • Parent cell: 2n=2; Results in 2 daughter cells

  • Post-mitosis: tracking of chromosomes and chromatids

    • Anaphase: 4 chromatids present

Human Cells: Chromosome Tracking During Mitosis

Phase

# Chromosomes

# Chromatids

Prophase

46

92

Metaphase

46

92

Anaphase

92

92

Telophase

92

92

End of Mitosis

46

46

Review Questions

  • Identify stages of mitosis:

  1. Prophase

  2. Anaphase

  3. Metaphase

  4. Telophase

  • Structure labeled "X": Options are Centriole, Spindle, Chromosome, Chromatid

Additional Review

  • During which phase do chromosomes first become visible? Options:A. InterphaseB. TelophaseC. MetaphaseD. Prophase

  • Structure responsible for moving chromosomes during mitosis:A. NucleolusB. Nuclear membraneC. SpindleD. Cytoplasm

Analysis Questions

  • Anaphase movement affected by a drug preventing:A. Nuclear envelope breakdownB. Cell wall formationC. Elongation of microtubulesD. Shortening of microtubulesE. Formation of cleavage furrow

  • If sperm cell contains 12 chromosomes, organism has: A. 4B. 8C. 12D. 16E. 24

Practice FRQ

  • Cell has 50 chromosomes; after division, one daughter cell has 49 and the other 51.

    • Possible reason: Anaphase failure to attach spindle fibers, resulting in lagging chromosome.