Mitosis and Meiosis

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Mitosisand Meiosis
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Mitosis Cell Division

• In each human cell there are 23 unique
  chromosomes each containing thousands of genes.
• Most cells in the human body have 2 copies of
  every chromosome
• These cells are called diploid (2n).

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Mitosis

• In order to keep the same genetic information
  cells undergo a process of division that ensures
  the same information is passed from parent to
  offspring.

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A) Cell Cycle
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A) Cell Cycle

• The life cycle of a cell has 2 portions
  Interphase and Mitosis.
• Interphase is the normal condition of a cell.
  During this time the cell does its job and
  prepares for division.
• Mitosis is the process of division.

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A) Cell Cycle

• Interphase has 3 steps
• G1- The cell produces proteins and performs its
  normal functions in the body.
• S DNA inside the nucleus replicates.
• G2 The cell resumes growth/function and readies
  for division.

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B) Mitosis

• Mitosis is divided into 4 steps
• Prophase
• Metaphase
• Anaphase
• Telophase
• After Mitosis Cytokinesis occurs, which is the
  division of the cytoplasm.

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Mitosis Prophase

• The nuclear envelop breaks down
• Chromatin condenses into chromosomes (Xs)
• Spindle fibers begin migrating to opposite ends.

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Mitosis Metaphase

• The individual chromosomes line up at the center
  ? metaphase plate
• Centrioles and spindles are at opposite ends of
  the cell and connected to every pair of
  chromosomes at the centromere.

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B) Mitosis Anaphase

• The centrioles pull on the spindles and separate
  the chromatids to opposite sides.

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B) Mitosis Telophase

• The chromatids are now in opposite ends of the
  cell and they begin to decondense.
• Nuclear membrane begins to reform.
• Spindles break down.

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B) Mitosis Cytokinesis

• In animals proteins pinch off the center of the
  cell into 2 each parts, seperating the cytoplasm.

• In plants the Golgi synthesizes a new cell wall
  along the metaphase plate, creating 2 separate
  cells.

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C) Meiosis

• In sex cells cell division is different.
• The process must half the number of chomosomes in
  each cell.
• This allows for fertilization to recreate the
  complete number of chromosomes.

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C) Meiosis

• The process of meiosis is called a reduction
  division.
• There are 2 rounds of division with some slight
  differences.

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C) Meiosis
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C) Meiosis

• The first round of meiosis has the following
  steps Prophase I, Metaphase I, Anaphase I, and
  Telophase I.
• The second round of division is made up of
  Prophase 2, Metaphase II, Anaphase 2, and
  Telophase 2.

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C) Meiosis

• Differences
• During Prophase I homologous chromosomes pair up
  at the metaphase plate!
• There is NO DNA duplication between Meiosis I and
  II, so the DNA never has a chance to double.
• The end result is 4 haploid cells instead of 2
  diploid cells.

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C) Meiosis