25 dna mitosis-2008
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25 dna mitosis-2008






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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

25 dna mitosis-2008 25 dna mitosis-2008 Presentation Transcript

  • Biology is the only subject in which multiplication is the same thing as division…Regents Biology 2006-2007
  • Making New Cells Making New DNARegents Biology 2006-2007
  • Where it all began… You started as a cell smaller than a period at the end of a sentence…Regents Biology
  • And now look at you… How did you get from there toRegents Biology here?
  • Getting from there to here…  Going from egg to baby…. the original fertilized egg has to divide… and divide… and divide… and divide…Regents Biology
  • Why do cells divide…  for reproduction  one celled organisms (clones) amoeba  for growth & development  from fertilized egg to multi-celled organism  for repair starfish  replace cells that die from normal wear & tear or from injury QuickTimeª and a TIFF (Uncompressed) decompressor are needed to see this picture.Regents Biology
  • Dividing cells…  What has to be copied  DNA  organelles  cell membrane  lots of other molecules  enzymesRegents Biology plant cell animal cell
  • Copying DNA  A dividing cell duplicates its DNA  creates 2 copies of all DNA  separates the 2 copies to opposite ends of the cell  splits into 2 daughter cells  But the DNA starts DNA loosely wound in cell the nucleus  If you tried to divide it like that, it couldRegents Biology nucleus tangle & break
  • Organizing & packaging DNADNA cell nucleus DNA has been “wound up”DNA in chromosomes in celleveryday “working” cell nucleus4 chromosomes DNA in chromosomes in cellin this organismRegents Biology getting ready to divide
  • Chromosomes of Human Female 46 chromosomes 23 pairsRegents Biology
  • Chromosomes of Human Male 46 chromosomes 23 pairsRegents Biology
  • Paired bases  DNA structure  double helix  2 sides like a ladder  Bases match together  A pairs with T A:T  C pairs with G C:GRegents Biology
  • Watson and CrickRegents Biology
  • Copying DNA  Matching bases allows DNA to be easily copiedRegents Biology
  • Making new DNA  Copying DNA  replication  DNA starts as a double-stranded molecule  matching bases (A:T, C:G)  then it unzips…Regents Biology
  • DNA replication  Strands “unzip” at the weak bonds between basesRegents Biology
  • DNA replication DNA bases in nucleus  Enzyme  DNA polymerase DNA  adds new bases polymeraseRegents Biology
  • Copying DNA  Build daughter DNA strand  use original parent strand as “template”  add new matching bases  synthesis enzyme = DNA polymerase DNA PolymeraseRegents Biology
  • New copies of DNA  Get 2 exact copies of DNA to split between new cells DNA polymerase DNA polymeraseRegents Biology
  • Copied & Paired Up Chromosomes centromereRegents Biology
  • Copying & packaging DNA  When cell is ready to divide…  copy DNA first, then…  coil up doubled chromosomes like thread on a spool…  now can move DNA around cell without having it tangle & break Coil DNA intoRegents Biology Copying DNA compact chromosomes
  • double-strandedhuman chromosomesready for mitosisRegents Biology
  • DNA must be duplicated… chromosomes in cell DNA in chromosomes cell 4 single-stranded chromosomes duplicated chromosomes nucleus duplicated cell chromosomes4 double-stranded chromosomesRegents Biology nucleus
  • Mitosis: Dividing DNA & cells  Stage 1: cell copies DNA DNA Copy DNA! cell nucleusRegents Biology (interphase)
  • Mitosis: Dividing DNA & cells  Stage 2: DNA winds into chromosomes  DNA is wound up into chromosomes to keep it organizedduplicated chromosomes Wind up! cell nucleusRegents Biology (prophase)
  • Mitosis: Dividing DNA & cells  Stage 3: Chromosomes line up  chromosomes line up in middle  attached to protein “cables” that will help them move Line up! duplicated chromosomes lined up in middle of cellRegents Biology (metaphase)
  • Mitosis: Dividing DNA & cells  Stage 4: Chromosomes separate  chromosomes split, separating pairs  start moving to opposite ends Separate! chromosomes split & move to opposite endsRegents Biology (anaphase)
  • Mitosis: Dividing DNA & cells  Stage 5: Cell starts to divide  cells start to divide  nucleus forms again Divide!Regents Biology (telophase)
  • Mitosis: Dividing DNA & cells  Stage 6: DNA unwinds again  cells separate  now they can do their every day jobs Bye Bye!Regents Biology (cytokinesis)
  • New “daughter” cells  Get 2 exact copies of original cells  same DNA  “clones”Regents Biology
  • Cell division in AnimalsRegents Biology
  • Mitosis in whitefish embryoRegents Biology
  • Mitosis in plant cellRegents Biology
  • onion root tipRegents Biology
  • Overview of mitosis Copy DNA Wind Up Bye-Bye!Regents Biology Line Up Separate Divide
  • Any Questions?? Any Questions??Regents Biology 2006-2007
  • And now look at you… How did you get from there toRegents Biology here?