Cell division


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Cell division

  1. 1. Chapter 8 Cell Division Mitosis Meiosis
  2. 2. Cell DivisionWhat is it? Why doCells do it? Why is itimportant to me?
  3. 3. Cell Division Also known as Mitosis Takes place inRegular Body CellsKeeps Cells Living and Growing
  4. 4. Phases of Mitosis
  5. 5. MitosisThe Basic Phases of a Cell’s Life: •Interphase •Prophase •Metaphase •Anaphase •Telophase •Cytokinesis
  6. 6. InterphaseThe longest stage of a Cell’s life The time spentbetween divisions Produces allmaterials required for growth Preparation for division
  7. 7. Part ofInterphase isalso knownas the G1Phase of theCell Cycle(GrowthPhase)
  8. 8. The Secondpart ofInterphase isknown as theS Phase of theCell Cycle(SynthesisPhase – whenDNAduplicates)
  9. 9. Go to DNA PowerPoint• You need to know all about DNA before we can move on with cell division!!!
  10. 10. The third partof the CellCycle, G2, isjust acheckpoint tomake sure theDNA is correct. Next step – Mitosis
  11. 11. Mitosis: Cell DivisionThe last part ofthe Cell Cycleis calledMitosis andhas 4 phasesduring whichthe cell dividesinto 2 cells
  12. 12. ProphaseThe Cell begins the division process1. The nucleolus disappears,2. The nuclear membrane breaks apart
  13. 13. 3. The chromosomes become visible4. The spindle apparatus forms and attaches to the centromeres of the chromosomes
  14. 14. Metaphase The Second Phase of Mitosis1. The Nuclear Membrane is completely gone2. The duplicated chromosomes line up along the cells equator.
  15. 15. AnaphaseThe third phase ofMitosisDiploid sets of daughterchromosomes separateThey are pushed andpulled toward oppositepoles of the cell by thespindle fibers
  16. 16. Spindle Fibers
  17. 17. TelophaseThe nuclearmembrane andnucleoli (nucleus)reform.Cytokinesis isnearly complete,
  18. 18. The Cell Platebegins to formThe Cellprepares forfinial division
  19. 19. Cytokinesis – The final stage of Mitosis The cytoplasm, organelles, and nuclear material are evenly split and two new cells are formed.Cell Plate
  20. 20. The two new cells – each exactly like theother – are called Daughter Cells
  21. 21. Quick Review:The following slides are drawings of thestages of Mitosis. On your notes, pleasedraw each phase and label it.
  22. 22. Interphase – The Cell spends the majority ofits life here, growing and functioning. Duringthe S Phase of the Cell Cycle, the DNAreplicates, in anticipation of Mitosis
  23. 23. In Early Prophase of Mitosis the Chromosomes get small, centrioles move to the poles of the nucleus, and spindle fibers develop Chromosomes consisting of 2Pair of SisterCentrioles Chromatids Spindle Fibers
  24. 24. Late Prophase happens when theNuclear Envelope disintegrates andspindle fibers begin to moveChromosomes toward the center of cell. Spindle Fibers Chromosomes
  25. 25. During Metaphase the Chromosomes lineup across center of the cell, also called theequator, or Metaphase plate. Spindle Fibers Equator, or Metaphase Plate Chromosomes
  26. 26. In Anaphase the Chromatids that make up eachChromosome move apart and travel to oppositeends of cellular spindle Daughter Chromosomes Chromatid Chromosome
  27. 27. In Telophase an envelope surrounds each set ofChromatids to form new Nucleus and theCytoplasm starts to divide Cleavage Furrow
  28. 28. Cytokinesis takes place when the Cytoplasmdivides and two cells with identical geneticmaterial are formed Daughter Cells
  29. 29. Quick Review – Place Cells in Mitosis Order A B C D E
  30. 30. Interphase Quick Review: Identify What happens in each Prophase phase of Mitosis: Metaphase Anaphase Telophase
  31. 31. Why Do Cells Divide? The larger a cell becomes, the more demands the cell places on its DNA. It also has more trouble moving enough food and wastes across its cell membrane.
  32. 32. Food goes in The bigger the cell gets the harder it becomes to move food and waste across the membrane Waste goes out
  33. 33. Protein Pumps This happens because the surface area and volume ratio does not stay the same as the cell size increases.
  34. 34. The cells abilityto either getsubstancesfrom theoutside oreliminate wastefrom the insideis related to thesurface area ofthe cellmembrane.(outside)
  35. 35. How much foodand othermaterial isrequired, andhow muchwaste the cellproduces andhas to get ridof, is related tothe volume ofthe cell. (inside)
  36. 36. As a cell getsbigger therecomes a timewhen its surfacearea is not largeenough to meetthe demands ofthe cells volumeand the cell stopsgrowing.
  37. 37. So, once cellsreach a certainsize they mustdivide in order tocontinue tofunction – or theywill no longer beable to take innutrients andeliminate waste.
  38. 38. Why Is Cell Division Important?1. All Living Things are made of Cells
  39. 39. 2. The Cell is the basic unit of Structure andFunction in Living Things.
  40. 40. 3. All Cells come from pre existing Cells
  41. 41. You are a livingorganism, made ofcells.In order to keepliving, your cellsmust stay alive.In order for cells tokeep living, theymust divide andmultiply
  42. 42. MeiosisWhy We Are Who We Are
  43. 43. MeiosisTakes place in the Gametes of an organismPeople have a Chromosome count of 46When an egg joins a sperm the count must stay at46 to remain humanSo, the egg can only have 23 chromosomes, andthe sperm can only have 23 chromosomesBut, the integrity of the organism must bemaintained.How does this happen?
  44. 44. During Meiosis gamete (sex) cells undergo a “double division”, maintaining the DNA, but reducing the chromosomal count to 23 + =Sperm (23) + Egg (23) = Fertilized Cell (46)
  45. 45. Chromosome Chromosomes atafter S Phase beginning of Mitosis After After Mitosis Meiosis
  46. 46. Original Gamete Metaphase Anaphase Telophase Cytokinesis2 Daughter Cells Metaphase 2 Anaphase 2 Telophase 2 Cytokinesis – 4 Gametes
  47. 47. At the end of Meiosisthe individual Gametecell has divided fromone cell to four.Males produce 4viable sperm.Females produce 1viable egg and 3 nonfunctioning polarbodies.
  49. 49. Meiosisensures that all living organismswill maintainboth GeneticDiversity and Genetic Integrity