AP Bio Ch. 12, Cell cycle

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AP Bio Ch. 12, Cell cycle

  1. 1. The Cell Cycle & Mitosis Ch. 12
  2. 2. Main goals for this lecture 1. Distinguish between chromosomes, chromatids, and chromatin 2. Correctly model and identify in pictures each stage of the cell cycle
  3. 3. The Main Ideas 1. Cell division results in 2 genetically identical daughter cells 2. The mitotic phase alternates with interphase in the cell cycle
  4. 4. The unity of life • All living things reproduce • Reproduction occurs at the cellular level
  5. 5. The many functions of cell division • REPRODUCTION: In unicellular organisms leads to an increase in the size of the population • In multicellular organisms – GROWTH: a single fertilized egg (zygote) divides to form a new organism – REPAIR: Repairs and renews old or damaged cells
  6. 6. Cell Division results in identical daughter cells • The DNA is copied and divided between the 2 new cells • Each new cell (daughter) contains an exact copy of the original DNA • In human cells, there is about 6 feet of DNA to copy and neatly and accurately divide between the 2 new cells!
  7. 7. Quick Think What is the purpose of mitosis?
  8. 8. DNA • A cell’s genetic information is called its genome – In bacteria (prokaryotic cells) it is usually 1 long circular DNA molecule – In plants, animals, and fungi (eukaryotic cells) is it usually several linear molecules of DNA
  9. 9. Chromosomes • The individual molecules of DNA are packaged into chromosomes • Each species has a characteristic number of chromosomes – – – – – – Humans - 46 Camel 70 Alligator - 32 Chicken - 78 King crab - 208 Corn - 20
  10. 10. Quick Think Is the complexity of the organisms directly proportional to the number of chromosomes? Explain your answer.
  11. 11. Chromosomes • Chromosomes are made of chromatin – DNA + proteins • THE DNA PART: Each chromosome is a single long piece of DNA coding for 100s or 1000s of genes
  12. 12. Chromosomes • THE PROTEIN PART: the proteins help keep the shape of the chromosome and help control the activity of the genes
  13. 13. Quick Think • So…what’s a chromosome? • • • • What is it made of? What is it’s purpose? Where is it found? How many do we have?
  14. 14. Chromosomes • When the cell is dividing the DNA is tightly packed into X-shaped chromosomes • When the cell is not dividing, the DNA is more loose - just chromatin strands
  15. 15. Quick Think • How does the appearance of chromatin and chromosomes vary? • Draw them…?
  16. 16. Getting the DNA ready for cell division • Before a cell divides, the DNA (chromatin) condenses and • folds into a neat, tightly packed chromosome Each chromosome is made up of 2 sister chromatids identical copies of that particular chromosome
  17. 17. Chromosomes • The 2 sister chromatids are attached with sticky proteins • The place where they are attached is called the centromere
  18. 18. Quick Think Distinguish between chromatin, chromosomes, and chromatids?
  19. 19. Chromosomes • During cell division, the 2 sister chromatids are pulled apart to opposite ends of the cell and repackaged into new nuclei • They are now considered individual chromosomes
  20. 20. Mitosis • The formation of 2 daughter nuclei Notice ! Not • Followed by the 2 new cells. 2 new division of the nuclei . cytoplasm and organelles called cytokinesis
  21. 21. Mitosis and Interphase • Mitotic (M) phase - ~10% of a cell’s life • Interphase - ~90% of a cell’s life
  22. 22. Interphase • During this time the cell: – grows – produces proteins & organelles – copies its chromosomes – Prepares for cell division
  23. 23. Interphas e • 3 phases: – G1 phase = first gap • Cell is making proteins and organelles – S phase = synthesis • Cell is making proteins and organelles • DNA IS COPIED – G2 phase = second gap • Cell is making proteins and organelles
  24. 24. Mitosis • 5 subphases: – – – – – Prophase Prometaphase Metaphase Anaphase Telophase
  25. 25. What happens in each phase • At the end of interphase: – DNA has been copied – DNA not in chromosomes yet – Nucleus intact – The centrosome (an organelle that helps organize the mitotic spindle fibers) replicates
  26. 26. What happens in each phase • Prophase: – – – – Chromosomes now tightly coiled Sister chromatids joined together Nucleoli disappear Mitotic spindle begins to form
  27. 27. What happens in each phase • Prometaphase: – Nuclear membrane breaks up – Microtubles from spindle start to connect with chromosomes – Each sister chromatid has a kinetochore protein in the centromere where the spindle fiber attaches
  28. 28. • What is the primary difference between prophase and prometaphase?
  29. 29. What happens in each phase • Metaphase: – The spindle fibers push the sister chromatids until they are all lined up at the metaphase plate (the middle of the cell)
  30. 30. What happens in each phase • Anaphase: – The sister chromatids are pulled apart by the spindle fibers
  31. 31. What happens in each phase • Telophase: – New daughter nuclei begin to form around each set of chromosomes – Chromosomes start to unwind
  32. 32. Quick Think Explain what happens to the chromosomes during mitosis
  33. 33. What happens in each phase • Cytokinesis: – Division of the cytoplasm – In animal cells, the two new cells “pinch” apart – In plant cells, a new cell wall forms between the 2 new daughter cells
  34. 34. What phase is this cell in?
  35. 35. Mitosis Modeling • One chromosome before the DNA has been copied
  36. 36. Mitosis Modeling • 2 chromosomes AFTER the DNA has been copied
  37. 37. Mitosis Modeling • 1 sister chromatid
  38. 38. Mitosis Modeling • Centromere
  39. 39. Mitosis Modeling • Interphase – G1
  40. 40. Mitosis Modeling • Interphase – S
  41. 41. Mitosis Modeling • Interphase – G2
  42. 42. Mitosis Modeling • Prophase
  43. 43. Mitosis Modeling • Prometaphase
  44. 44. Mitosis Modeling • Metaphse
  45. 45. Mitosis Modeling • Anaphase
  46. 46. Mitosis Modeling • Telophase
  47. 47. Mitosis Modeling • Cytokinesis
  48. 48. Chromosome Challenge! • With your chromosomes….show me: • Metaphase
  49. 49. Chromosome Challenge! • With your chromosomes….show me: • Early Anaphase
  50. 50. Chromosome Challenge! • With your chromosomes….show me: • Late Anaphase
  51. 51. Chromosome Challenge! • With your chromosomes….show me: • End of Telophase
  52. 52. Chromosome Challenge! • With your chromosomes….show me: • A cell before it has copied the DNA
  53. 53. Chromosome Challenge! • With your chromosomes…show me: • All four stages with the people in your row…in order

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