this is a chapter about DNA and RNA structure,

1. Genetics: Analysis and Principles By Robert J. Brooker CHAPTER 9 Molecular structure of DNA and RNA

2. Roles of the genetic material “ The genetic material must carry out two jobs: duplicate itself and control the development of the rest of the cell in a specific way” Francis Crick

6. Discovery of a “transforming principle” Frederick Griffith, 1928 Pneumonia ( Diplococcus pneumoniae ) infecteren muizen. Muizen krijgen longontsteking en sterven . Twee type bacteriën : R bacterie “rough coat”: - geen ontsteking S bacterie “smooth coat”- wel ontsteking “ Coat type is associated with virulence”. Healthy Mouse

7. Griffith’s experiment identifying the “transforming principle” Injection Bacterial colonies Rough nonvirulent (strain R) Results Mouse healthy Smooth virulent (strain S) Mouse dies Heat-killed smooth virulent (strain S) Live strain S bacteria in blood sample from dead mouse Mouse dies Mouse healthy + Rough nonvirulent (strain R) Heat-killed smooth virulent (strain S)

8. What is the “transforming principle”? Conclusion: DNA is the transforming principle allowing R bacteria to make a smooth coat and allow infection. Oswald Avery, Colin MacLeod and Maclyn McCarty, 1944 Heat-killed S bacteria “transformed” the R bacteria to a form that causes pneumonia

10. 05_04_Avery_MacLeod.jpg

11. Hershey and Chase Results

13. virus particle labeled with 35 S DNA ( blue ) being injected into bacterium 35 S remains outside cells virus particle labeled with 32 P DNA ( blue ) being injected into bacterium 35 P remains inside cells Fig 9b 225 Hershey and Chase Results

21. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 9.10 Base always attached here Phosphates are attached there

25. 09_06.jpg James Watson Francis Crick

26. DNA nucleotide bases phosphate group deoxyribose ADENINE (A) THYMINE (T) CYTOSINE (C) GUANINE (G)

27. Figure 9.11

28. Phosphodiester bond

30. Esscher A The strands are Anti-parallel B The strands are complementary C The mechanism for copying lies within its structure Three important features of DNA

32. Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 9.17

33. 9-49 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 9.18

35. 9-56 Figure 9.21 DNA wound around histone proteins

38. Bases substantially tilted relative to the central axis Bases substantially tilted relative to the central axis Sugar-phosphate backbone follows a zigzag pattern Bases relatively perpendicular to the central axis No details

41. Figure 9.22

45. Figure 9.23 Also called hair-pin Complementary regions Held together by hydrogen bonds Have bases projecting away from double stranded regions Noncomplementary regions

46. Example: 3D structure of tRNA-Phe from yeast

47. RNAs are folded into complex structures because of their ability to form internal duplexes M.McManus Hairpin Loops Stems Bulge loop Interior loops Multi-branched loop

48. Divalent cations, Mg ++ , are essential for correct folding, stability, and catalysis. (example: >100 Mg 2+ ions needed for the folding of RNAse P

49. 1. Identification of DNA as the Genetic Material 1. Experiments with pneumococcus suggested that DNA is the genetic material 2. Hershey and Chase provided evidence that the genetic material injected into the bacterial cytoplasm is T2 phage DNA 3. RNA functions as the genetic material in some viruses 2. Nucleic acid structure 1. Nucleotides are the building blocks of nucleic acids 2. Nucleotides are linked together to form a strand 3. A few key events led to the discovery of the double helix structure 4. Chargaff found that DNA has a biochemical composition in which the amount of A equals T and the amount of G equals C 5. Watson and Crick deduced the double helical structure of DNA 6. The molecular structure of the DNA double helix has several key features 7. DNA can form alternative types of double helices 8. DNA can form a triple helix, called triplex DNA 9. The three-dimensional structure of DNA within chromosomes requires additional folding and the association with proteins 10. RNA molecules are composed of strands that fold into specific structures Summary : Outline of this chapter 9