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2 7.1 - dna structure hl

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  • 1. DP Biology 11 Unit 7.1 DNA Structure HL
  • 2. DNA Structure
    • Features of DNA double helix
    • Antiparallel strands:
      • The two strands have their 3’ and 5’ terminals at opposite ends
    • 5’ - 3’ linkages
      • At one end of each DNA strand is a phosphate group linked to carton atom 5 of deoxyribose
      • At one end of each DNA is a hydroxyl group attached to carbon atom 3 of deoxyribose
  • 3. DNA Structure
    • Features of DNA double helix
    • Nucleotides linked by covalent bonds
      • Between the 5’ phosphate group and the 3’ carbon atom of the other nucleotide
    • Hydrogen bonding
      • Between purines and pyrimidines
        • A purine can only bond with a pyrimidine and vice versa
  • 4. DNA Structure
    • Features of DNA double helix
    • Nitrogenous base
      • Pyrimadines
        • A one-ring structure (CUT the pie!)
        • Cytosine, Thymine, and Uracil
          • U replaces T in RNA
      • Purines
        • A two-ring structure
        • Guanine and Adenine
  • 5. DNA Structure
  • 6. DNA Structure
  • 7. DNA Structure
  • 8. DNA Structure
    • Nucleosome structure
    • Grooves on the diameter of the double helix
      • Expose compounds that can hydrogen bond
      • Thus, DNA is bonded to proteins, called histones
  • 9. DNA Structure
    • Nucleosome structure
    • Histone proteins :
      • Eight histone proteins fit together perfectly
        • 4 types, 2 of each type
        • DNA wraps around this core twice
  • 10. DNA Structure
    • Nucleosome structure
    • Histone proteins :
      • 1 histone protein outside each nucleosome
        • Organizes and holds the nucleosome together
  • 11. DNA Structure
    • Nucleosome structure
    • Nucleosome
      • A structure for coiling DNA by combining it with histone proteins
      • DNA is wrapped twice around each nucleosome
  • 12. DNA Structure
    • Nucleosome structure
    • Nucleosome
      • DNA is wound around and hydrogen bonded to eight histones
        • 146 DNA bases or 1.65 turns of the helix are associated with the 8 histones
      • The combination of DNA and histones is secured by the 'H1 linker' protein
        • 9 proteins total
  • 13. DNA Structure
    • Nucleosome structure
    • Nucleosome
  • 14. DNA Structure
    • Supercoiling
    • Uncoiled DNA is around 1.8 meters long
      • Coiled to be moved around the cell during mitosis
      • Partially uncoiled during transcription
      • Nucleosomes aid in both these actions
  • 15. DNA Structure
    • Supercoiling
    • For mitosis, DNA is coiled16,000x
      • DNA wraps twice around a histone proteins
      • These nucleosomes wrap around each other
      • These strands wrap around each other forming coils
      • These stack one upon another in a coil
      • = supercoiling
  • 16. DNA Structure
  • 17. DNA Structure
  • 18. DNA Structure
    • Single-copy vs. repetitive nuclear DNA
    • Unique or single-copy genes
      • Code for mRNA which codes for polypeptides
        • Around 25,000 different proteins
      • About 1.5 % of our DNA
  • 19. DNA Structure
    • Single-copy vs. repetitive nuclear DNA
    • Highly repetitive sequences
      • Also called satellite DNA
      • Constitute 5-45% of the genome
      • Sequences are 5-300 base pairs per repeat
      • May be repeated up to 10,000 times per genome
      • Function of repetitive DNA is not known
      • Repetitive sequences vary from person to person
        • Useful in DNA profiling
  • 20. DNA Structure
  • 21.  
  • 22. DNA Structure
    • Eukaryotic DNA: Exons and Introns
    • Eukaryotic organisms have DNA which differs from prokaryotic organism
      • Have exons and introns
  • 23. DNA Structure
    • Eukaryotic DNA: Exons and Introns
    • Exons :
      • Regions of DNA that are translated into proteins
    • Introns :
      • Non-coding regions within the gene
      • These are copied when the gene is transcribed to produce pre-mRNA
      • The intron-RNA is edited out to form mature mRNA
  • 24. DNA Structure
    • Eukaryotic DNA: Introns and Exons
  • 25. ANIMATION
  • 26.  
  • 27. TOK QUESTION:
    • Power of LABELS
    • Highly repetitive sequences were once classified as “junk DNA”, showing a degree of confidence that it had no role.
    • To what extent do the labels and categories used in the pursuit of knowledge affect the knowledge we obtain?
    • SEE: “Failed states” in Politics, “Tracking” in Education, “Bad students/kids” in Parenting and Schools, “Day names” in Africa
  • 28. MAJOR SOURCES
    • Thank you to my favorite sources of information when making these lectures!
    • John Burrell (Bangkok, TH) www.click4biology.info
    • Dave Ferguson (Kobe, JA)
    • http://canada.canacad.ac.jp/High/49
    • Stephen Taylor (Bandung, IN)
    • www.i-biology.net
    • Andrew Allott – Biology for the IB Diploma
    • C. J.Clegg – Biology for the IB Diploma
    • Weem, Talbot, Mayrhofer – Biology for the International Baccalaureate
    • Howard Hugh’s Medical Institute – www.hhmi.org/biointeractive
    • Mr. Hoye’s TOK Website – http://mrhoyestokwebsite.com
    • And all the contributors at www.YouTube.com