G. Holmes Braddock High School

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Mitosis Meiosis

• G. Holmes Braddock High School

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Lesson Guide

• Mitosis
• Meiosis
• Cell Cycle
• Sexual Asexual Reproduction
• Genetic Variation and Cancer

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Mitosis

• Mitosis is the process in which the division of
  cells occurs. Mitosis happens in all cells except
  sex cells. Before mitosis the cells chromosomes
  double(turns into diploid cell). then half when
  the cell splits, leaving the original number of
  chromosomes in the two new daughter cells(forming
  two new haploid cells).
• Interphase (Cell Cycle) The cell grows and
  doubles its chromosomes.
• Prophase The chromatin inside the nucleus
  condenses into chromosomes while spindle fibers
  begin to form at opposite ends/poles of the
  cell.
• Metaphase As the spindle fibers fully develop
  they stretch out towards the center of the cell.
  The chromosomes of the cell move towards the
  metaphase plate (center of the cell).

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Mitosis

• Anaphase The paired chromosomes divide into
  chromatids and begin to be pulled towards
  opposite ends of the cell by the spindle fibers.
• Telophase New nuclei form at the two ends of
  the cell with their corresponding chromosomes.
  The cell begins to divide into its two new
  daughter cells.
• Cytokinesis The cell is completely divided in
  two, forming two new daughter cells.

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Meiosis

• Meiosis is the process of cell division in sex
  cells. Similar to mitosis, when a cell undergoes
  meiosis, it first doubles its chromosomes before
  it splits and divides into two new cells, ending
  meiosis 1. The new cells then begin meiosis 2.
  During meiosis 2 the cells do not multiply their
  chromosomes before splitting, both cells divide
  creating four new daughter cells each containing
  half the amount of chromosomes of an original
  cell. These new daughter cells are called
  gametes, also known as the sperm cells in males
  and the egg cells in females.
• Meiosis 1
• Interphase In this stage the cell grows and
  doubles its chromosomes.

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Meiosis

• Prophase I Homologous chromosomes pair up
  forming tetrads, while spindle fibers begin to
  form at opposite ends/poles of the cell.
• Metaphase I As the spindle fibers fully develop
  they stretch out towards the center of the cell.
  The chromosomes of the cell move towards the
  metaphase plate (center of the cell).
• Anaphase I The paired chromosomes divide into
  chromatids and begin to be pulled towards
  opposite poles of the cell by the spindle fibers.
• Telophase I New nuclei form at the two ends of
  the cell with their corresponding chromosomes.
  The cell divides into two new daughter cells
  which then immediately begin Meiosis 2.

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Meiosis

• Meiosis 2
• Prophase II The spindle fibers begin to
  reappear.
• Metaphase II The chromosomes line up the the
  cells center. Each sister chromatids point toward
  the opposite poles its cell.
• Anaphase II The sister chromatids are separated
  by the spindle fibers and move towards the
  opposite poles of the cell.
• Telophase II The cells begin to divide once
  more and forming new distinct nuclei.
• Cytokinesis The cells divide into four new
  daughter cells with half the number of
  chromosomes of the original parent cell.

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Cell Cycle

• The cell cycle is is the life cycle of a cell and
  shows the choices the cell makes during its
  life. The cell cycle consists of an interphase
  state and a cell division state(ONLY mitosis is
  involved in the cell cycle since meiosis is not a
  cycle).
• Interphase
• G1 Phase (Gap 1) In this gap the cell increases
  in size while producing RNA and protein. It also
  ensures the it is ready for DNA synthesis.
• S Phase (Synthesis) A copy of the cells DNA is
  made in order to later on create two similar
  daughter cells.
• G2 Phase (Gap 2) During this gap the cell
  continues to grow and produce protein. The cell
  then checks if it is ready to go into mitosis.

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Cell Cycle

• Mitosis
• The cell undergoes mitosis and divides creating
  two new daughter cells.
• G0 Phase (Gap 0) The cell will, at times, leave
  the cycle and stop duplicating. The cell does
  this to rest or stops permanently because it is
  at an end in its development.

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• Asexual Reproduction

• Sexual Reproduction

• The asexual form of reproduction is mitosis.
  Mitosis replicates a mother cell into two
  daughter cells which are identical. This is
  asexual reproduction because no other cell is
  needed in order to reproduce.

• The sexual form of reproduction is meiosis.
  Meiosis replicates the mother cells chromosomes
  into two daughter cells. Those cells then divide
  their chromosomes randomly into four new cells,
  creating cells similar to the mother cell but not
  identical.

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Genetic Variation

• Genetic variation only occurs through meiosis,
  not mitosis. This is because mitosis involves the
  making of identical cells, while meiosis consists
  of factors like independent assortment and
  cross-overs.
• Independent assortment divides the chromosomes in
  cells randomly creating a varied result of sex
  cells.
• Cross-overs increase the varied factor.

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Cancer

• Mutation in cells can cause their reproduction
  rate to go out of control. This mutation can
  comes from chemicals, radiation, or viruses.
• The rapid reproduction of cells creates tumors.
  Which then can lead to cancer unless the tumor is
  benign or non-invasive.
• Cancer is caused when the cells of tumors invade
  other neighboring tissues or enter the blood
  stream.