Cell Division and the Cell Cycle

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Cell Division and the Cell Cycle
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Cell Division

• Why does cell division occur so often?
• Replacement of old cells.
• Growth
• Cancer
• Mother cells
• Daughter cells

• Prokaryotic cell division
• Prokaryotic fission
• DNA attached directly to cell membrane.
• Replicated
• Cell membrane grows and separates the 2 circular
  chromosomes

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Eukaryotic Cell Division

• Mitosis
• Meiosis
• Cytokinesis
• Roles
• Before division can occur
• Organelles must be replicated and sorted.
• DNA must be replicated and sorted.

• Many chromosomes are involved.
• Chromatin
• Chromatids
• Centromere
• Mitotic chromosome
• Histones
• Homologues
• Homologous chromosomes
• Haploid (1N)
• Diploid (2N)

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Mitosis and Meiosis

• Dance of the chromosomes
• Happens all of the body.
• Roles
• Makes new somatic cells
• Replaces dead cells.
• Growth
• Repair
• Asexual Reproduction

• Meiosis
• Occurs only in the gametes.
• Creates haploid cells from diploid cells (germ
  cells).
• Creates gametes or reproductive cells

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The Cell Cycle

• Interphase
• G1
• S
• G2
• M phase
• Mitosis and cytokinesis

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Cell Cycle and Mitosis

• Rate of cell cycle
• Varies with cell type
• Hormones and growth factors regulate the rate.
• Cancer
• Interphase
• Appearance of cell

• Mitosis
• Phases
• Prophase
• Chromosomes form, spindle forms (centrioles),
  nuclear membrane dissolves, nucleolus disappears.

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Phases of Mitosis

• Metaphase
• Chromosomes line up in middle of the cell.
• Connect to spindle fibers via kinetochores.
• Anaphase
• Spindle fibers help to pull apart sister
  chromatids. These then move toward opposite
  spindle poles

• Telophase
• Chromosomes reach opposite poles. Chromosomes
  unwind. Nuclear membrane forms around each set
  of chromosomes. Spindle is dismantled.
  Nucleolus reappears.
• Opposite of prophase

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Cytokinesis

• Happens after mitosis.
• In animals Cleavage furrow forms due to the
  contraction of the microfilaments of the
  cytoskeleton. Like a noose. Cells eventually
  pull apart into 2 identical cells.
• In plants A cell plate forms between the 2 new
  nuclei. This eventually forms a cell wall that
  separates 2 identical cells.

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