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1 3.3 - dna structure


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1 3.3 - dna structure

  1. 1. DP Biology 11 Unit 3.3 DNA Structure
  2. 2. DNA Structure
  3. 3. DNA Structure <ul><li>Nucleotide structure </li></ul><ul><li>Sugar </li></ul><ul><ul><li>Deoxyribose </li></ul></ul><ul><li>Phosphate group </li></ul><ul><ul><li>PO 4 -3  group </li></ul></ul><ul><li>Nitrogenous base </li></ul><ul><ul><li>4 different kinds of ring-based structures </li></ul></ul>
  4. 4. DNA Structure <ul><li>Nucleotide structure </li></ul><ul><li>Nitrogenous base </li></ul><ul><ul><li>C  Cytosine </li></ul></ul><ul><ul><li>G  Guanine </li></ul></ul><ul><ul><li>A  Adenine </li></ul></ul><ul><ul><li>T  Thymine </li></ul></ul>
  5. 5. DNA Structure
  6. 6. DNA Structure <ul><li>General structure </li></ul><ul><li>Backbone: </li></ul><ul><ul><li>Phosphate group of one nucleotide attaches to the third (3’) carbon of the deoxyribose in the next </li></ul></ul><ul><ul><li>Deoxyribose - Phosphate - Deoxyribose – Phosphate - etc... </li></ul></ul><ul><ul><li>Nitrogenous base attached to deoxyribose </li></ul></ul>
  7. 7. DNA Structure <ul><li>General structure </li></ul>
  8. 8. DNA Structure
  9. 9. DNA Structure <ul><li>Formation of the DNA double helix </li></ul><ul><li>Complementary base paring : </li></ul><ul><ul><li>A = T </li></ul></ul><ul><ul><ul><li>Adenine forms two hydrogen bonds with its complementary base, thymine </li></ul></ul></ul><ul><ul><li>G = C: </li></ul></ul><ul><ul><ul><li>Guanine forms three hydrogen bonds with its complementary base, cytosine </li></ul></ul></ul>
  10. 10. DNA Structure
  11. 11. DNA Structure <ul><li>Formation of the DNA double helix </li></ul><ul><li>Hydrogen bonds : </li></ul><ul><ul><li>Hydrogen bonds between A = T and G = C hold the two strands of DNA together </li></ul></ul><ul><ul><li>Each strand forms a helix, the two strands together form a double helix </li></ul></ul>
  12. 12. DNA Structure
  13. 13. DNA Structure
  14. 14. DNA Structure
  15. 15. DNA Structure <ul><li>This is image shows: </li></ul><ul><li>Two polynucleotide chains </li></ul><ul><li>Two anti-parallel chains </li></ul><ul><ul><li>The two chains are in opposite directions </li></ul></ul><ul><li>A uniform distance (2nm) between the backbones </li></ul><ul><li>Complementary base pairs: </li></ul><ul><ul><li>Adenine hydrogen binds to Thymine </li></ul></ul><ul><ul><li>Cytosine hydrogen bonds to Guanine </li></ul></ul>
  16. 16. DNA Structure <ul><li>This is image shows: </li></ul><ul><li>DNA is double-stranded, </li></ul><ul><ul><li>The strands are antiparallel, </li></ul></ul><ul><li>The strands are wound round each other to form a double helix ( not a spiral ) </li></ul><ul><li>The two strands are joined together by  hydrogen bonds  between the bases </li></ul><ul><ul><li>Follow commplementarity </li></ul></ul><ul><ul><li>Sequence on one strand complementary to the other </li></ul></ul>
  17. 17. TOK QUESTION: <ul><li>PLAGIARISM in science! </li></ul><ul><li>To what extent was Watson and Crick’s “discovery” of the three dimensional structure of DNA dependent on the use of data generated by Rosalind Franklin, which was shared without her knowledge or consent? </li></ul><ul><li>Do they deserve full credit? </li></ul>
  18. 18. 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>