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2 7.1 - dna structure hl


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2 7.1 - dna structure hl

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