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Biology is the only subject in which multiplication is the same thing as division …

Biology is the only subject in which multiplication is the same thing as division …. Making New Cells Making New DNA. Where it all began…. You started as a cell smaller than a period at the end of a sentence…. And now look at you…. How did you get from there to here?.

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Biology is the only subject in which multiplication is the same thing as division …

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  1. Biology is the only subject in which multiplication is the same thing as division…

  2. Making New CellsMaking New DNA

  3. Where it all began… You started as a cell smaller than a period at the end of a sentence…

  4. And now look at you… How did you get from there to here?

  5. Getting from there to here… • Going from egg to baby…. the original fertilized egg has to divide… and divide… and divide… and divide…

  6. Why do cells divide… • for reproduction • one celled organisms (clones) • for growth & development • fromfertilized eggto multi-celled organism • for repair • replace cells that die from normal wear & tear or from injury amoeba starfish

  7. Dividing cells… • What has to be copied • DNA • organelles • cell membrane • lots of othermolecules • enzymes plant cell animal cell

  8. 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 loosely wound in the nucleus • If you tried to divide it like that, it could tangle & break DNA cell nucleus

  9. Organizing & packaging DNA DNA cell DNA has been “wound up” nucleus DNA in chromosomes ineveryday “working” cell cell nucleus 4 chromosomesin this organism DNA in chromosomes in cell getting ready to divide

  10. Chromosomes of Human Female 46 chromosomes 23 pairs

  11. Chromosomes of Human Male 46 chromosomes 23 pairs

  12. 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 : G

  13. Watson and Crick

  14. Copying DNA • Matching bases allows DNA to be easily copied

  15. Making new DNA • Copying DNA • replication • DNA starts as a double-stranded molecule • matching bases (A:T, C:G) • then it unzips…

  16. DNA replication • Strands “unzip” at the weak bonds between bases

  17. DNA replication • Enzyme • DNA polymerase • adds new bases DNA basesin nucleus DNA polymerase

  18. Copying DNA • Build daughter DNA strand • use original parent strand as “template” • add new matching bases • synthesis enzyme = DNA polymerase DNA Polymerase

  19. DNA polymerase DNA polymerase New copies of DNA • Get 2 exact copies of DNA to split between new cells

  20. Copied & Paired Up Chromosomes centromere

  21. Coil DNA into compact chromosomes Copying DNA 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

  22. double-strandedhuman chromosomes ready for mitosis

  23. chromosomes in cell DNA in chromosomes cell 4 single-stranded chromosomes duplicated chromosomes nucleus duplicated chromosomes cell nucleus 4 double-stranded chromosomes DNA must be duplicated…

  24. Mitosis: Dividing DNA & cells • Stage 1: cell copies DNA Copy DNA! DNA cell nucleus (interphase)

  25. Mitosis: Dividing DNA & cells • Stage 2: DNA winds into chromosomes • DNA is wound up into chromosomes to keep it organized duplicated chromosomes Wind up! cell nucleus (prophase)

  26. 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 cell (metaphase)

  27. Mitosis: Dividing DNA & cells • Stage 4: Chromosomes separate • chromosomes split, separating pairs • start moving to opposite ends Separate! chromosomes split & move to opposite ends (anaphase)

  28. Mitosis: Dividing DNA & cells • Stage 5: Cell starts to divide • cells start to divide • nucleus forms again Divide! (telophase)

  29. Mitosis: Dividing DNA & cells • Stage 6: DNA unwinds again • cells separate • now they can do their every day jobs Bye Bye! (cytokinesis)

  30. New “daughter” cells • Get 2 exact copies of original cells • same DNA • “clones”

  31. Cell division in Animals

  32. Mitosis in whitefish embryo

  33. Mitosis in plant cell

  34. onion root tip

  35. Overview of mitosis Copy DNA Wind Up Bye-Bye! Line Up Separate Divide

  36. Any Questions?? Any Questions??

  37. And now look at you… How did you get from there to here?

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