What are the steps in mitosis?

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What are the steps in mitosis?

• Goal
• Explain what happens in each step in mitosis

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Mitotic Phase Cell is dividing
M
1. Prophase
- Chromosomes begin to coil and become visible in
the nucleus as two sister chromatids joined at
the centromere
Prophase
- Nuclear membrane breaks down
- Chromosomes are scattered throughout cytoplasm
- Spindle fibers form between centrioles and each
centromere
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• Chromosomes condense and become more compact and
  visible.
• Nuclear membrane breaks apart and nucleoli
  disappear.  

Prophase
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- chromosomes are manipulated by spindle fibers
attached at the centromere
- Chromosomes line up on the mid-line of the cell
(called the Metaphase plate)
Metaphase
(The chromatids will split apart at their
centromeres, with each replicated chromosome
giving rise to two daughter chromosomes.)
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3. Anaphase
- Sister chromatids separate at their centromeres
each chromatid is now a chromosome
- Chromosomes move to opposite ends of the cell
(there is now a complete set of chromosomes at
each end)
Anaphase
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Telophase

• Chromosomes uncoil into chromatin.
• New nuclear membrane forms around BOTH groups of
  chromosomes nucleoli reform in each nucleus.
• Spindle fibers disappear.
• (Cell pinches in middle to begin formation of two
  cells.)

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Cytokinesis

• Cytokinesis Division of the Cytoplasm
• Cytokinesis divides structures within the
  cytoplasm (ribosmes, Golgi apparatus,
  mitochondria, etc.)

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Cytokinesis

• In animal cells cleavage furrow forms at the
  metaphase plate to pinch cytoplasm in two.
• In plant cells, cell plate is formed during
  cytokinesis (cell plate eventually becomes cell
  wall.)

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Cytokinesis
2. Cytokinesis
- NOT a part of mitosis
- Division of the cytoplasm
-Results in two identical daughter cells, each
with exact copies of the parent cells genetic
material
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Function of Mitosis

• Single celled organisms
• Allows these organisms to reproduce asexually.
• Single celled organisms are able to grow in
  population.

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• Multicellular organisms
• Allows these organisms to grow in size and
  maintain surface are to volume ratio.
• Allow for specialization through cell
  differentiation.
• Cells that are dead and damaged can be replaced.

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Regulation of the Cell Cycle
What controls the Cell Cycle? 1) Environmental
Factors pH, nutrients, temperature, etc. 2)
Density of cells density-dependent
inhibitioncell will not divide if it is crowded,
must also be attached to a surface to divide
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Abnormal Cell Division

• Cancer--uncontrolled division of cells.
• Cells do not respond to normal cell division
  controls.
• Cells divide indefinitely without aging and
  dying.

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• Transformationnormal cell is converted to a
  cancer cell.
• If the immune system does not destroy this cancer
  cell it divides to form a tumor
• Tumor is benign if it remains in the same place.
  A malignant tumor has the ability to spread.
• Metastasiscancer cells enter the circulatory
  system and spread to all parts of the body.