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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

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.