Biology is the only subject       in which multiplication is       the same thing as division…AP Biology                  ...
The Cell Cycle:             Cell Growth, Cell DivisionAP Biology                                2007-2008
Where it all began…     You started as a cell smaller than     a period at the end of a sentence…AP Biology
And now look at you…                        How did you                       get from thereAP Biology                to h...
Cell division  Cytoplasmic  Nuclear      Reducible      Non reducible        Mitosis is normal cell division, which g...
Why do cells divide?    For reproduction            asexual reproduction              one-celled organisms    For grow...
Making new cells     Nucleus         chromosomes         DNA     Cytoskeleton            centrioles              in ...
DNA         Nucleus     Function                                                 chromosome        protects DNA         ...
Cytoskeleton     Function            structural support               maintains shape of cell               provides a...
Cytoskeleton                        actin                        microtubule                        nucleiAP Biology
AP Biology
Centrioles      Cell division            in animal cells, pair of centrioles             organize microtubules          ...
 What is passed on to daughter cells?            exact copy of genetic material = DNA              mitosisAP Biology
Overview of mitosis    interphase   prophase    (pro-metaphase)                                    cytokinesisAP Biology  ...
Interphase     90% of cell life cycle         cell synthesize proteins/enzymes         prepares for duplication if trig...
M                                                      Mitosis   Cell cycle                               G2              ...
Interphase       Divided into 3 phases:                      G0                G1 = 1st Gap (Growth)                   ...
S phase: Copying / Replicating DNA    Synthesis phase of Interphase        dividing cell replicates DNA        must sep...
ACTGGTCAGGCAATGTC                                                DNA   Organizing DNA      DNA is organized in        chr...
Copying DNA & packaging it…     After DNA duplication, chromatin condenses            coiling & folding to make a smalle...
Note:   Chromosomes exist in 2 different      states, before and after they replicate      their DNA.          Before rep...
Mitotic Chromosome      Duplicated chromosome           2 sister chromatids           narrow at centromeres           ...
Mitosis     Dividing cell’s DNA between       2 daughter nuclei      4 phases          prophase          metaphase    ...
Cell CycleAP Biology           24
green = key features   Prophase     Chromatin condenses            visible chromosomes               chromatids     Ce...
green = key features   Transition to Metaphase     Prometaphase            spindle fibers attach to             centrome...
green = key features   Metaphase      Chromosomes align        along middle of cell            metaphase plate          ...
AP Biology
green = key features   Anaphase   Sister chromatids separate at     kinetochores       move to opposite poles       pul...
Separation of chromatids    In anaphase, proteins holding together sister      chromatids are inactivated          separ...
Chromosome movement     Kinetochores use        motor proteins that        “walk” chromosome        along attached       ...
green = key features   Telophase      Chromosomes arrive at        opposite poles          daughter nuclei form         ...
Cytokinesis      Animals            constriction belt of             actin microfilaments             around equator of ...
Cytokinesis     The     organelles      (other   than    the       chromosomes) get divided up into the 2       daughter ...
Any Questions??AP Biology                 2007-2008
Control of Cell CycleAP Biology
Phases of the cell cycle                              {                     G1 (gap 1)Interphase          S (synthesis)-...
Cell cycle checkpoints      Control mechanisms that ensure the         fidelity of cell division in eukaryotic cells.    ...
Cell cycle checkpoints      An       important   function   of     many         checkpoints is to assess DNA damage,     ...
Progression of the cell cycle is regulated    by feedback from intracellular eventsAP Biology
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Lecture on Mitosis

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  • Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents
  • Centromeres are segments of DNA which have long series of tandem repeats = 100,000s of bases long. The sequence of the repeated bases is quite variable. It has proven difficult to sequence.
  • Microtubules are NOT reeled in to centrioles like line on a fishing rod. The motor proteins walk along the microtubule like little hanging robots on a clothes line. In dividing animal cells, non-kinetochore microtubules are responsible for elongating the whole cell during anaphase, readying fro cytokinesis
  • Division of cytoplasm happens quickly.
  • Lecture on Mitosis

    1. 1. Biology is the only subject in which multiplication is the same thing as division…AP Biology 2007-2008
    2. 2. The Cell Cycle: Cell Growth, Cell DivisionAP Biology 2007-2008
    3. 3. Where it all began… You started as a cell smaller than a period at the end of a sentence…AP Biology
    4. 4. And now look at you… How did you get from thereAP Biology to here?
    5. 5. Cell division  Cytoplasmic  Nuclear  Reducible  Non reducible  Mitosis is normal cell division, which goes on throughout life in all parts of the body.  Meiosis is the special cell division that creates the sperm and eggs, the gametes. We will discuss meiosis separately.AP Biology
    6. 6. Why do cells divide?  For reproduction  asexual reproduction  one-celled organisms  For growth  from fertilized egg to multi-celled organism amoeba  For repair & renewal  replace cells that die from normal wear & tear or from injuryAP Biology
    7. 7. Making new cells  Nucleus  chromosomes  DNA  Cytoskeleton  centrioles  in animals  microtubule spindle fibersAP Biology
    8. 8. DNA Nucleus  Function chromosome protects DNA  histone protein  Structure  nuclear envelope  double membrane  membrane fused in spots to create pores  allows large macromolecules to pass through nuclear pores nuclear pore What kind of molecules need to pass through? nucleolusAP Biology nuclear envelope
    9. 9. Cytoskeleton  Function  structural support  maintains shape of cell  provides anchorage for organelles  protein fibers  microfilaments, intermediate filaments, microtubules  motility  cell locomotion  cilia, flagella  regulation  organizes structuresAP Biology & activities of cell
    10. 10. Cytoskeleton  actin  microtubule  nucleiAP Biology
    11. 11. AP Biology
    12. 12. Centrioles  Cell division  in animal cells, pair of centrioles organize microtubules  spindle fibers  guide chromosomes in mitosisAP Biology
    13. 13.  What is passed on to daughter cells?  exact copy of genetic material = DNA  mitosisAP Biology
    14. 14. Overview of mitosis interphase prophase (pro-metaphase) cytokinesisAP Biology metaphase anaphase telophase
    15. 15. Interphase  90% of cell life cycle  cell synthesize proteins/enzymes  prepares for duplication if triggered Time to divide & multiply!AP Biology
    16. 16. M Mitosis Cell cycle G2 Gap 2 G1  Cell has a “life cycle” Gap 1 G0 cell is formed from S Resting a mitotic division Synthesiscell grows & matures cell grows & matures to divide again to never divide again G1, S, G2, M liver cells G1→G0 epithelial cells, brain / nerve cells blood cells, muscle cells stem cellsAP Biology
    17. 17. Interphase  Divided into 3 phases: G0  G1 = 1st Gap (Growth)  cell doing its “everyday job” o n al tesig ivid  S = DNA Synthesis d  copies chromosomes  G2 = 2nd Gap (Growth)  prepares for division  cell grows (more)  produces organelles, proteins, membranesAP Biology
    18. 18. S phase: Copying / Replicating DNA  Synthesis phase of Interphase  dividing cell replicates DNA  must separate DNA copies correctly to 2 daughter cells  human cell duplicates  each daughter cell gets complete identical copyAP Biology
    19. 19. ACTGGTCAGGCAATGTC DNA Organizing DNA  DNA is organized in chromosomes histones  double helix DNA molecule  wrapped around histone proteins  like thread on spools  DNA-protein complex = chromatin chromatin  organized into long thin fiber  condensed further during mitosis double stranded chromosomeAP Biology duplicated mitotic chromosome
    20. 20. Copying DNA & packaging it…  After DNA duplication, chromatin condenses  coiling & folding to make a smaller package DNA mitotic chromosome chromatinAP Biology
    21. 21. Note:  Chromosomes exist in 2 different states, before and after they replicate their DNA. Before replication, chromosomes have one chromatid. After replication, chromosomes have 2 sister chromatids, held together at the centromere. Each chromatid is one piece of DNA with its supporting proteins.  In mitosis, the two chromatids of each chromosome separate, with each chromatid going into a daughter cell.  Remember that diploid cells have two copies of each chromosome, one from each parent. These pairs of chromosomes are NOT attached together.AP Biology
    22. 22. Mitotic Chromosome  Duplicated chromosome  2 sister chromatids  narrow at centromeres  contain identical copies of original DNA homologous homologouschromosomes chromosomes sister chromatidssingle-stranded AP Biology double-stranded homologous = “same information”
    23. 23. Mitosis  Dividing cell’s DNA between 2 daughter nuclei  4 phases  prophase  metaphase  anaphase  telophaseAP Biology
    24. 24. Cell CycleAP Biology 24
    25. 25. green = key features Prophase  Chromatin condenses  visible chromosomes  chromatids  Centrioles move to opposite poles of cell  Protein fibers cross cell to form mitotic spindle  microtubules  actin, myosin  coordinates movement of chromosomes  Nuclear membrane breaks downAP Biology
    26. 26. green = key features Transition to Metaphase  Prometaphase  spindle fibers attach to centromeres  creating kinetochores  connect centromeres to centrioles  chromosomes begin movingAP Biology
    27. 27. green = key features Metaphase  Chromosomes align along middle of cell  metaphase plate  meta = middle  spindle fibers coordinate movement  helps to ensure chromosomes separate properly  so each new nucleus receives only 1 copy of each chromosomeAP Biology
    28. 28. AP Biology
    29. 29. green = key features Anaphase  Sister chromatids separate at kinetochores  move to opposite poles  pulled at centromeres  pulled by motor proteins “walking”along microtubules  actin, myosin  increased production of ATP by mitochondria  Poles move farther apart  polar microtubules lengthenAP Biology
    30. 30. Separation of chromatids  In anaphase, proteins holding together sister chromatids are inactivated  separate to become individual chromosomes 1 chromosome 2 chromosomes 2 chromatids single-strandedAP Biologydouble-stranded
    31. 31. Chromosome movement  Kinetochores use motor proteins that “walk” chromosome along attached microtubule  microtubule shortens by dismantling at kinetochore (chromosome) endAP Biology
    32. 32. green = key features Telophase  Chromosomes arrive at opposite poles  daughter nuclei form  nucleoli form  chromosomes disperse  no longer visible under light microscope  Spindle fibers disperse  Cytokinesis begins  cell divisionAP Biology
    33. 33. Cytokinesis  Animals  constriction belt of actin microfilaments around equator of cell  cleavage furrow forms  splits cell in two  like tightening a draw stringAP Biology
    34. 34. Cytokinesis  The organelles (other than the chromosomes) get divided up into the 2 daughter cells passively: they go with whichever cell they find themselves in.  Plant and animal cells divide the cytoplasm in different ways.  In plant cells, a new cell wall made of cellulose forms between the 2 new nuclei, about where the chromosomes lined up in metaphase. Cell membranes form along the surfaces of this wall. When the new wall joins with the existing side wall, the 2 cells have become separate.  In animal cells, a ring of actin fibers (microfilaments are composed of actin) forms around the cell equator and contacts, pinching the cell in half.AP Biology
    35. 35. Any Questions??AP Biology 2007-2008
    36. 36. Control of Cell CycleAP Biology
    37. 37. Phases of the cell cycle  { G1 (gap 1)Interphase  S (synthesis)- doubling  G2 (gap 2)  M (mitosis)- halving G1  C (cytokinesis) S G2AP Biology
    38. 38. Cell cycle checkpoints  Control mechanisms that ensure the fidelity of cell division in eukaryotic cells.  These checkpoints verify whether the processes at each phase of the cell cycle have been accurately completed before progression into the next phase.  Multiple checkpoints have been identified, though some of them are less understood than others.AP Biology
    39. 39. Cell cycle checkpoints  An important function of many checkpoints is to assess DNA damage, which is detected by sensor mechanisms.  When damage is found, the checkpoint uses a signal mechanism either to stall the cell cycle until repairs are made or, if repairs cannot be made, to target the cell for destruction via apoptosis (effector mechanism).AP Biology
    40. 40. Progression of the cell cycle is regulated by feedback from intracellular eventsAP Biology

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