Cell Division & Mitosis
 Section 4.1 - Cell Reproduction
Why is Cell Division Important?

•               billions
    Everyday _________________ of red blood cells wear
    out and are replaced.

•              millions
    Everyday _________________ of skin cells wear out and
    are replaced.

• Cell division is how single cell organisms reproduce.
Why is Cell Division Important?
      How do little elephants grow
        up to be BIG elephants?
          Cell Division
Cell Division & the Cell Cycle




Mitosis is a cycle that occurs in most of our cells.
Length of a Cycle
• The cell cycle is a series of events that takes place
  from one cell division to the next.

• The time it takes to complete a cell cycle is not the
  same in all cells.
Mitosis & Asexual Reproduction
• Mitosis is the process in which the nucleus divides
  to form two new nuclei.

• Mitosis is a form of asexual reproduction.
• Asexual Reproduction
  - when a cell doubles its contents and then divides
  into two identical cells
  - the production of offspring that are genetically
  identical
Mitosis & Asexual Reproduction
• The process of asexual reproduction begins after a
  sperm fertilizes an egg.
Why Asexual Reproduction?

3 reasons why cells
reproduce asexually:

• growth
• repair
• replacement
Steps of Mitosis
• Interphase
• PROPHASE
• METAPHASE
• ANAPHASE
• TELOPHASE
• Cytokinesis
Steps of Cell Cycle
• Interphase
• PROPHASE
• METAPHASE
• ANAPHASE
• TELOPHASE
• Cytokinesis
How can I remember the order?

  I Pray More At The Church
Interphase
• Most of the life of any eukaryotic cell is spent in a
  period of growth and development called
  interphase.

• Cells in your body that no longer divide, such as
  nerve and muscle cells, are always in interphase.

• An actively dividing cell, such as a skin cell, copies
  its hereditary material and prepares for cell division
  during interphase.
Interphase
• During interphase, each chromosome duplicates.
• When the nucleus is ready to divide, each duplicated
  chromosome coils tightly into two thickened, identical
  strands called chromatids.
Chromosome
• A chromosome is a structure in the nucleus that
  contains hereditary material (DNA).

• A chromatid is one-half of a replicated chromosome.
Chromosome
Chromosome
Chromosome
Chromosome
Chromosome


  chromosome
_________________




                                 chromatid
Interphase
animal cell     plant cell
Prophase

• The pairs of
  chromatids are fully
  visible when viewed
  under a microscope.

• The nucleolus and the
  nuclear membrane
  disintegrate.
Prophase

• Two small structures
  called centrioles move to
  opposite ends of the cell.

• Between the centrioles,
  spindle fibers begin to
  stretch across the cell.
Prophase


• Plant cells also form
  spindle fibers during
  mitosis but do not have
  centrioles.
Prophase
animal cell     plant cell
Metaphase
• The pairs of chromatids
  line up across the
  center of the cell.

• The centromere of each
  pair usually becomes
  attached to two spindle
  fibers—one from each
  side of the cell.
Metaphase
animal cell    plant cell
Anaphase
• Each centromere divides and the spindle fibers shorten.
Anaphase
• Each pair of chromatids separates, and chromatids
  begin to move to opposite ends of the cell.
Anaphase
animal cell    plant cell
Telophase

• The spindle fibers
  start to disappear.
• The chromosomes
  start to uncoil.
• A new nucleus
  forms.
Telophase
animal cell     plant cell
Cytokinesis - division of cytoplasm

  • For most cells,
    after the nucleus
    has divided, the
    cytoplasm
    separates and two
    new cells are
    formed.
Cytokinesis - division of cytoplasm

• In animal cells, the
  cell membrane
  pinches in the middle,
  like a balloon with a
  string tightened
  around it, and the
  cytoplasm divides.
Cytokinesis - division of cytoplasm
• In plant cells, the
  appearance of a
  cell plate tells you
  that the cytoplasm
  is being divided.

• Why is this step
  different for plant
  cells?
Cytokinesis - division of cytoplasm
• New cell walls form
  along the cell plate,
  and new cell
  membranes develop
  inside the cell walls.

• Now, the period of
  growth, or interphase,
  begins again.
Cytokinesis - division of cytoplasm
Cytokinesis
animal cell      plant cell
Animal Mitosis -- Review
   Interphase    Prophase




  Metaphase      Anaphase




   Telophase    Interphase
Plant Mitosis -- Review
   Interphase      Prophase




  Metaphase        Anaphase




   Telophase       Interphase
Results of Mitosis
4 important things to remember about Mitosis & Cell Division
1. Mitosis is the division of a nucleus.
2. Mitosis produces 2 new nuclei that are identical to the
   original nucleus
   • Every cell in your body copies the same hereditary information.
   • All of your cells use different parts (genes) of the same
      hereditary material to become different types of cells.
3. The original cell no longer exists.
4. Cell division allows growth and replaces worn out or
   damaged cells.
Other forms of
        Asexual Reproduction
• Bacteria cannot reproduce through mitosis because
  of what mitosis is. Mitosis is the division of a
  nucleus.

• Bacteria do not have a nucleus, so they cannot
  undergo mitosis.

• The process they use is called fission.
Fission
• Binary fission is the
  simplest form of asexual
  reproduction.

• Bacteria cells split into
  approximately two equal
  halves. The process in
  bacteria is relatively
  rapid.
Fission

• The two new organisms
  are identical genetically,
  except for a random
  mutation that may
  occasionally occur.
Budding
• Hydra, a freshwater
  animal, reproduces using
  budding. The bud is an
  exact copy of the adult
  plant.

• Part of the adult buds off,
  or breaks off, and a new
  organism grows.
Regeneration
Regeneration replaces lost body parts. It uses mitosis
and cell division.
Cell Division and Mitosis (4.1)

Cell Division and Mitosis (4.1)

  • 1.
    Cell Division &Mitosis Section 4.1 - Cell Reproduction
  • 3.
    Why is CellDivision Important? • billions Everyday _________________ of red blood cells wear out and are replaced. • millions Everyday _________________ of skin cells wear out and are replaced. • Cell division is how single cell organisms reproduce.
  • 4.
    Why is CellDivision Important? How do little elephants grow up to be BIG elephants? Cell Division
  • 5.
    Cell Division &the Cell Cycle Mitosis is a cycle that occurs in most of our cells.
  • 6.
    Length of aCycle • The cell cycle is a series of events that takes place from one cell division to the next. • The time it takes to complete a cell cycle is not the same in all cells.
  • 7.
    Mitosis & AsexualReproduction • Mitosis is the process in which the nucleus divides to form two new nuclei. • Mitosis is a form of asexual reproduction. • Asexual Reproduction - when a cell doubles its contents and then divides into two identical cells - the production of offspring that are genetically identical
  • 8.
    Mitosis & AsexualReproduction • The process of asexual reproduction begins after a sperm fertilizes an egg.
  • 9.
    Why Asexual Reproduction? 3reasons why cells reproduce asexually: • growth • repair • replacement
  • 10.
    Steps of Mitosis •Interphase • PROPHASE • METAPHASE • ANAPHASE • TELOPHASE • Cytokinesis
  • 11.
    Steps of CellCycle • Interphase • PROPHASE • METAPHASE • ANAPHASE • TELOPHASE • Cytokinesis
  • 12.
    How can Iremember the order? I Pray More At The Church
  • 13.
    Interphase • Most ofthe life of any eukaryotic cell is spent in a period of growth and development called interphase. • Cells in your body that no longer divide, such as nerve and muscle cells, are always in interphase. • An actively dividing cell, such as a skin cell, copies its hereditary material and prepares for cell division during interphase.
  • 14.
    Interphase • During interphase,each chromosome duplicates. • When the nucleus is ready to divide, each duplicated chromosome coils tightly into two thickened, identical strands called chromatids.
  • 15.
    Chromosome • A chromosomeis a structure in the nucleus that contains hereditary material (DNA). • A chromatid is one-half of a replicated chromosome.
  • 16.
  • 17.
  • 18.
  • 19.
  • 20.
  • 21.
  • 22.
    Prophase • The pairsof chromatids are fully visible when viewed under a microscope. • The nucleolus and the nuclear membrane disintegrate.
  • 23.
    Prophase • Two smallstructures called centrioles move to opposite ends of the cell. • Between the centrioles, spindle fibers begin to stretch across the cell.
  • 24.
    Prophase • Plant cellsalso form spindle fibers during mitosis but do not have centrioles.
  • 25.
  • 26.
    Metaphase • The pairsof chromatids line up across the center of the cell. • The centromere of each pair usually becomes attached to two spindle fibers—one from each side of the cell.
  • 27.
  • 28.
    Anaphase • Each centromeredivides and the spindle fibers shorten.
  • 29.
    Anaphase • Each pairof chromatids separates, and chromatids begin to move to opposite ends of the cell.
  • 30.
  • 31.
    Telophase • The spindlefibers start to disappear. • The chromosomes start to uncoil. • A new nucleus forms.
  • 32.
  • 33.
    Cytokinesis - divisionof cytoplasm • For most cells, after the nucleus has divided, the cytoplasm separates and two new cells are formed.
  • 34.
    Cytokinesis - divisionof cytoplasm • In animal cells, the cell membrane pinches in the middle, like a balloon with a string tightened around it, and the cytoplasm divides.
  • 35.
    Cytokinesis - divisionof cytoplasm • In plant cells, the appearance of a cell plate tells you that the cytoplasm is being divided. • Why is this step different for plant cells?
  • 36.
    Cytokinesis - divisionof cytoplasm • New cell walls form along the cell plate, and new cell membranes develop inside the cell walls. • Now, the period of growth, or interphase, begins again.
  • 37.
  • 38.
  • 39.
    Animal Mitosis --Review Interphase Prophase Metaphase Anaphase Telophase Interphase
  • 40.
    Plant Mitosis --Review Interphase Prophase Metaphase Anaphase Telophase Interphase
  • 42.
    Results of Mitosis 4important things to remember about Mitosis & Cell Division 1. Mitosis is the division of a nucleus. 2. Mitosis produces 2 new nuclei that are identical to the original nucleus • Every cell in your body copies the same hereditary information. • All of your cells use different parts (genes) of the same hereditary material to become different types of cells. 3. The original cell no longer exists. 4. Cell division allows growth and replaces worn out or damaged cells.
  • 43.
    Other forms of Asexual Reproduction • Bacteria cannot reproduce through mitosis because of what mitosis is. Mitosis is the division of a nucleus. • Bacteria do not have a nucleus, so they cannot undergo mitosis. • The process they use is called fission.
  • 44.
    Fission • Binary fissionis the simplest form of asexual reproduction. • Bacteria cells split into approximately two equal halves. The process in bacteria is relatively rapid.
  • 45.
    Fission • The twonew organisms are identical genetically, except for a random mutation that may occasionally occur.
  • 46.
    Budding • Hydra, afreshwater animal, reproduces using budding. The bud is an exact copy of the adult plant. • Part of the adult buds off, or breaks off, and a new organism grows.
  • 47.
    Regeneration Regeneration replaces lostbody parts. It uses mitosis and cell division.