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Chapter 12 (Part 1)
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Chapter 12 (Part 1)


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  • 1. Biology is the only subject in which multiplication is the same thing as division … 2007-2008
  • 2. The Cell Cycle: Cell Growth, Cell Division 2007-2008
  • 3. Where it all began… You started as a cell smaller than a period at the end of a sentence…
  • 4. Going from egg to baby…. the original fertilized egg has to divide… and divide… and divide… and divide… Getting from there to here…
  • 5. For reproduction asexual reproduction one-celled organisms For growth from fertilized egg to multi-celled organism For repair & renewal replace cells that die from normal wear & tear or from injury Why do cells divide? amoeba
  • 6. Making new cells Nucleus chromosomes DNA Cytoskeleton centrioles in animals microtubule spindle fibers
  • 7. Function protects DNA Structure nuclear envelope double membrane membrane fused in spots to create pores allows large macromolecules to pass through Nucleus What kind of molecules need to pass through? nuclear pores nuclear pore nuclear envelope nucleolus histone protein chromosome DNA
  • 8. Cytoskeleton Function structural support maintains shape of cell provides anchorage for organelles protein fibers microfilaments , intermediate filaments , microtubules motility cell locomotion cilia , flagella , etc. regulation organizes structures & activities of cell
  • 9. Cytoskeleton actin microtubule nuclei
  • 10. Centrioles Cell division in animal cells, pair of centrioles organize microtubules spindle fibers guide chromosomes in mitosis
  • 11. End of the Tour
  • 12. Getting the right stuff What is passed on to daughter cells? exact copy of genetic material = DNA mitosis organelles, cytoplasm, cell membrane, enzymes cytokinesis chromosomes (stained orange) in kangaroo rat epithelial cell  notice cytoskeleton fibers
  • 13. Overview of mitosis interphase prophase (pro-metaphase) metaphase anaphase telophase cytokinesis I.P.M.A.T.
  • 14. Interphase 90% of cell life cycle cell doing its “everyday job” produce RNA, synthesize proteins/enzymes prepares for duplication if triggered I’m working here ! Time to divide & multiply !
  • 15. Cell cycle Cell has a “life cycle” cell is formed from a mitotic division cell grows & matures to divide again cell grows & matures to never divide again G 1 , S, G 2 , M G 1  G 0 epithelial cells, blood cells, stem cells liver cells brain / nerve cells muscle cells
  • 16. Interphase Divided into 3 phases: G 1 = 1 st G ap ( G rowth) cell doing its “everyday job” cell grows S = DNA S ynthesis copies chromosomes G 2 = 2 nd G ap ( G rowth) prepares for division cell grows (more) produces organelles, proteins, membranes G 0 signal to divide
  • 17. Interphase Nucleus well-defined DNA loosely packed in long chromatin fibers Prepares for mitosis replicates chromosome DNA & proteins produces proteins & organelles green = key features
  • 18. Synthesis phase of Interphase dividing cell replicates DNA must separate DNA copies correctly to 2 daughter cells human cell duplicates ~3 meters DNA each daughter cell gets complete identical copy error rate = ~1 per 100 million bases 3 billion base pairs in mammalian genome ~30 errors per cell cycle mutations (to somatic (body) cells ) S phase: Copying / Replicating DNA
  • 19. Organizing DNA DNA is organized in chromosomes double helix DNA molecule wrapped around histone proteins like thread on spools DNA-protein complex = chromatin organized into long thin fiber condensed further during mitosis DNA histones chromatin duplicated mitotic chromosome ACTGGTCAGGCAATGTC double stranded chromosome
  • 20. Copying DNA & packaging it… After DNA duplication, chromatin condenses coiling & folding to make a smaller package DNA chromatin mitotic chromosome
  • 21. double-stranded mitotic human chromosomes
  • 22. Mitotic Chromosome Duplicated chromosome 2 sister chromatids narrow at centromeres contain identical copies of original DNA homologous = “same information” single-stranded double-stranded homologous chromosomes homologous chromosomes sister chromatids
  • 23. Mitosis Dividing cell’s DNA between 2 daughter nuclei “ dance of the chromosomes” 4 phases prophase metaphase anaphase telophase
  • 24. Prophase Chromatin condenses visible chromosomes chromatids Centrioles move to opposite poles of cell animal cell Protein fibers cross cell to form mitotic spindle microtubules actin, myosin coordinates movement of chromosomes Nucleolus disappears Nuclear membrane breaks down green = key features
  • 25. Transition to Metaphase Prometaphase spindle fibers attach to centromeres creating kinetochores microtubules attach at kinetochores connect centromeres to centrioles chromosomes begin moving green = key features
  • 26. 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 chromosome green = key features
  • 27. 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 lengthen green = key features
  • 28. Separation of chromatids In anaphase, proteins holding together sister chromatids are inactivated separate to become individual chromosomes 2 chromosomes 1 chromosome 2 chromatids single-stranded double-stranded
  • 29. Kinetochores use motor proteins that “walk” chromosome along attached microtubule microtubule shortens by dismantling at kinetochore (chromosome) end Chromosome movement
  • 30. 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 division green = key features
  • 31. Cytokinesis Animals constriction belt of actin microfilaments around equator of cell cleavage furrow forms splits cell in two like tightening a draw string
  • 32. Cytokinesis in Animals (play Cells Alive movies here) (play Thinkwell movies here)
  • 33. Mitosis in whitefish blastula
  • 34. Mitosis in animal cells
  • 35. Cytokinesis in Plants Plants cell plate forms vesicles line up at equator derived from Golgi vesicles fuse to form 2 cell membranes new cell wall laid down between membranes new cell wall fuses with existing cell wall
  • 36. Cytokinesis in plant cell
  • 37. Mitosis in plant cell
  • 38. onion root tip
  • 39. Evolution of mitosis Mitosis in eukaryotes likely evolved from binary fission in bacteria single circular chromosome no membrane-bound organelles Origin of replication chromosome: double-stranded DNA replication of DNA elongation of cell cell pinches in two ring of proteins
  • 40. Evolution of mitosis A possible progression of mechanisms intermediate between binary fission & mitosis seen in modern organisms protists dinoflagellates protists diatoms eukaryotes yeast eukaryotes animals prokaryotes (bacteria)
  • 41. Dinoflagellates algae “ red tide” bioluminescence
  • 42. Diatoms microscopic algae marine freshwater
  • 43. 2007-2008 Any Questions??
  • 44. Ghosts of Lectures Past (storage) 2007-2008
  • 45. Control of Cell Cycle
  • 46. Kinetochore Each chromatid has own kinetochore proteins microtubules attach to kinetochore proteins
  • 47. Chromosome structure nucleosome DNA histone DNA double helix chromosome rosettes of chromatin loops scaffold protein chromatin loop 30 nm
  • 48. Phases of a dividing cell’s life interphase cell grows replicates chromosomes produces new organelles, enzymes, membranes… G 1 , S, G 2 mitotic phase cell separates & divides chromosomes mitosis cell divides cytoplasm & organelles cytokinesis Cell Division cycle G 2 S G 1 M metaphase prophase anaphase telophase interphase (G 1 , S, G 2 phases) mitosis (M) cytokinesis (C) C
  • 49. Substitute Slides for Student Print version (for student note-taking) 2007-2008
  • 50. And now look at you… How did you get from there to here?