Bio celldivision-100106220037-phpapp01

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Bio celldivision-100106220037-phpapp01

  1. 1. Cell DivisionCell Division
  2. 2. ChromosomesChromosomes  Are made of DNAAre made of DNA  Each chromosome consists of sisterEach chromosome consists of sister chromatids attached at a centromerechromatids attached at a centromere
  3. 3. Cell CycleCell Cycle  During the cell cycle, a cell grows,During the cell cycle, a cell grows, prepares for division, and divides toprepares for division, and divides to form 2 daughter cells, each of whichform 2 daughter cells, each of which then begins the cycle again.then begins the cycle again.  Interphase – time for growth andInterphase – time for growth and regular cell activity.regular cell activity.  Most of a cell’s life is spent inMost of a cell’s life is spent in Interphase.Interphase.
  4. 4. InterphaseInterphase
  5. 5. Introduction to Cell DivisionIntroduction to Cell Division A time when a cell performs its usual functions, depending on the location in the body.
  6. 6. MitosisMitosis  The division of somatic or regularThe division of somatic or regular cells.cells.  Its divided into 4 phases.Its divided into 4 phases.  Remember Interphase is NOT part ofRemember Interphase is NOT part of Mitosis.Mitosis.
  7. 7. Introduction to MitosisIntroduction to Mitosis
  8. 8. ProphaseProphase  First stage of MitosisFirst stage of Mitosis  Chromatin condenses intoChromatin condenses into chromosomeschromosomes  Centrioles separate and a spindleCentrioles separate and a spindle fiber begins to form.fiber begins to form.  Nuclear membrane breaks downNuclear membrane breaks down
  9. 9. ProphaseProphase
  10. 10. MetaphaseMetaphase  Second Phase of MitosisSecond Phase of Mitosis  Chromosomes line up in the middleChromosomes line up in the middle of the cell.of the cell.  Each chromosome is connected to aEach chromosome is connected to a spindle fiber.spindle fiber.
  11. 11. MetaphaseMetaphase
  12. 12. AnaphaseAnaphase  Third Phase of MitosisThird Phase of Mitosis  The sister chromatids separate intoThe sister chromatids separate into individual chromosomes and moveindividual chromosomes and move apart to opposite ends of the cell.apart to opposite ends of the cell.
  13. 13. AnaphaseAnaphase
  14. 14. TelophaseTelophase  Fourth and Final Stage of MitosisFourth and Final Stage of Mitosis  Chromosomes gather at oppositeChromosomes gather at opposite ends of the cell and lose their distinctends of the cell and lose their distinct shapesshapes  Two new nuclear membranes haveTwo new nuclear membranes have formed.formed.
  15. 15. TelophaseTelophase
  16. 16. CytokinesisCytokinesis  The cytoplasm pinches in half.The cytoplasm pinches in half.  Each daughter cell has an identicalEach daughter cell has an identical set of duplicate chromosomesset of duplicate chromosomes
  17. 17. Regulating the CycleRegulating the Cycle  A protein called cyclin helps regulateA protein called cyclin helps regulate the cell cycle in eukaryotic cells.the cell cycle in eukaryotic cells.  They respond to internal andThey respond to internal and external events. These proteins areexternal events. These proteins are regulators.regulators.
  18. 18. When Things Go WrongWhen Things Go Wrong  Cancer cells do not respond to theCancer cells do not respond to the signals that regulate the growth ofsignals that regulate the growth of most cells.most cells.  As a result, they form masses of cellsAs a result, they form masses of cells called tumors that can damagecalled tumors that can damage surrounding tissues.surrounding tissues.
  19. 19. The Cell Cycle in DepthThe Cell Cycle in Depth  InterphaseInterphase  Mitotic StageMitotic Stage  CytokinesisCytokinesis  ApoptosisApoptosis  Cell Cycle and CancerCell Cycle and Cancer
  20. 20. INTERPHASEINTERPHASE  3 STAGES3 STAGES – GG11 stagestage – S StageS Stage – GG22 StageStage – Some cells such as nerve and muscleSome cells such as nerve and muscle cells typically do NOT complete the cellcells typically do NOT complete the cell cycle and are said to have entered thecycle and are said to have entered the GG00 stage.stage. – For adult mammalian cells, interphaseFor adult mammalian cells, interphase lasts ~20 hours (90% of cell cycle)lasts ~20 hours (90% of cell cycle)
  21. 21. INTERPHASE: GINTERPHASE: G11 stagestage  Stage BEFORE DNA replicationStage BEFORE DNA replication  Cell doubles its organelles andCell doubles its organelles and accumulates materials for DNAaccumulates materials for DNA synthesissynthesis  G used to stand for “gap” but now itG used to stand for “gap” but now it stands for “growth”stands for “growth” – Protein synthesis is a part of theseProtein synthesis is a part of these growth stagesgrowth stages
  22. 22. INTERPHASE: S stageINTERPHASE: S stage  DNA synthesis/replication occursDNA synthesis/replication occurs – Each chromosome is composed of oneEach chromosome is composed of one chromatid (DNA double helix) andchromatid (DNA double helix) and makes 2 sister chromatids (2 identicalmakes 2 sister chromatids (2 identical DNA double helix molecules)DNA double helix molecules)
  23. 23. INTERPHASE: GINTERPHASE: G22 stagestage  Stage from the completion of DNAStage from the completion of DNA replication to the onset of mitosisreplication to the onset of mitosis – The cell synthesizes protein that willThe cell synthesizes protein that will assist cell division (i.e. protein found inassist cell division (i.e. protein found in microtubules)microtubules)
  24. 24. M (Mitotic Stage)M (Mitotic Stage)  The cell division stage that includesThe cell division stage that includes mitosis (nuclear division) andmitosis (nuclear division) and cytokinesis (division of thecytokinesis (division of the cytoplasm)cytoplasm)
  25. 25. ProphaseProphase  Nucleolus is disappearingNucleolus is disappearing  Nuclear envelope is fragmentingNuclear envelope is fragmenting  Spindle is forming betweenSpindle is forming between centrosomescentrosomes  Asters radiate from the centriolesAsters radiate from the centrioles within the centrosomeswithin the centrosomes
  26. 26. PrometaphasePrometaphase  Kinetochores of sister chromatidsKinetochores of sister chromatids attach to kinetochore spindle fibersattach to kinetochore spindle fibers extending from opposite polesextending from opposite poles  Chromosomes move back and forthChromosomes move back and forth until they are aligned at theuntil they are aligned at the metaphase platemetaphase plate
  27. 27. MetaphaseMetaphase  Spindle is fully formedSpindle is fully formed  Duplicated chromosomes align atDuplicated chromosomes align at metaphase platemetaphase plate  Spindle consists of polar spindleSpindle consists of polar spindle fibers that overlap at the metaphasefibers that overlap at the metaphase plateplate  Kinetochore spindle fibers that areKinetochore spindle fibers that are attached to chromosomesattached to chromosomes
  28. 28. Anaphase  Sister chromatids separate to become daughter chromosomes that move toward the poles  Polar spindle fibers slide past one another  Kinetochore spindle fibers disassemble  Cytokinesis by furrowing begins
  29. 29. Telophase  Nuclear envelopes re-form  Chromosomes begin changing back to chromatin  Nucleoli reappear  Spindle disappears
  30. 30. Plant CellsPlant Cells  Lack centrioles and astersLack centrioles and asters  Mitotic spindle still forms and goesMitotic spindle still forms and goes through the same 5 mitotic phasesthrough the same 5 mitotic phases
  31. 31. CytokinesisCytokinesis  In animal cells, it’s a furrowingIn animal cells, it’s a furrowing process that divides the cytoplasmprocess that divides the cytoplasm  In plant cells, the formation of a cellIn plant cells, the formation of a cell plate from which the plasmaplate from which the plasma membrane and cell wall aremembrane and cell wall are completedcompleted
  32. 32. The Cell Cycle and CancerThe Cell Cycle and Cancer  Cancer is due to the mutation ofCancer is due to the mutation of genes that control the cell cyclegenes that control the cell cycle  Cancer cells are…Cancer cells are… – Are NondifferentiatedAre Nondifferentiated – Divide repeatedlyDivide repeatedly – Have abnormal nucleiHave abnormal nuclei – Don’t require growth factorsDon’t require growth factors – Not constrained by their neighborsNot constrained by their neighbors
  33. 33. The Cell Cycle and CancerThe Cell Cycle and Cancer  After forming a tumor, cancer cellsAfter forming a tumor, cancer cells metastasize and start new tumorsmetastasize and start new tumors elsewhere in body.elsewhere in body.  What you can do to try to preventWhat you can do to try to prevent cancer…cancer… – Avoid unnecessary radiationAvoid unnecessary radiation – Avoid exposure to organic chemicalsAvoid exposure to organic chemicals (ex: tobacco smoke)(ex: tobacco smoke) – Have a diet rich in fruits and vegetablesHave a diet rich in fruits and vegetables
  34. 34. Prokaryotic Cell DivisionProkaryotic Cell Division  Prokaryotic chromosome has a fewProkaryotic chromosome has a few proteins and a single, long loop of DNAproteins and a single, long loop of DNA  Binary fission- the chromosome attachesBinary fission- the chromosome attaches to the inside of the plasma membrane andto the inside of the plasma membrane and replicates.replicates.  As cell elongates, the chromosomes areAs cell elongates, the chromosomes are pulled apartpulled apart  Inward growth of the plasma membraneInward growth of the plasma membrane and formation of new cell wall materialand formation of new cell wall material divide the cell in 2.divide the cell in 2.
  35. 35. Prokaryotic vs. Eukaryotic CellsProkaryotic vs. Eukaryotic Cells  Binary fission (in prokaryotes) andBinary fission (in prokaryotes) and mitosis (in cellular eukaryotic protistsmitosis (in cellular eukaryotic protists and fungi) allow organisms toand fungi) allow organisms to reproduce asexuallyreproduce asexually  Mitosis in multicellular eukaryotes isMitosis in multicellular eukaryotes is primarily for the purpose ofprimarily for the purpose of development, growth, and repair ofdevelopment, growth, and repair of tissues.tissues.

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