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Outline of Next Six Lectures

Outline of Next Six Lectures. Lecture 16. Tues. Nov. 1: Structures of DNA and RNA. Lecture 17. Fri. Nov. 4: Recombinant DNA. Lecture 18. Tues. Nov. 8: Prokaryotic DNA Replication I. Lecture 19. Fri. Nov. 11: Prokaryotic DNA Replication II. Lecture 20.

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Outline of Next Six Lectures

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  1. Outline of Next Six Lectures Lecture 16 Tues. Nov. 1: Structures of DNA and RNA Lecture 17 Fri. Nov. 4: Recombinant DNA Lecture 18 Tues. Nov. 8: Prokaryotic DNA Replication I Lecture 19 Fri. Nov. 11: Prokaryotic DNA Replication II Lecture 20 Tues. Nov. 15: Eukaryotic DNA Replication I Fri. Nov. 18 TEST #3 (on Lectures 14-19) Lecture 21 Tues. Nov. 22: Eukaryotic DNA Replication II

  2. Nov. 1, 2005 MBB 694:407 & 115:511 Lecture 16: Structures of DNA and RNA

  3. The Beginning of the DNA Era DNA has a cool shape!

  4. I. Landmark Experiments in the Study of the Genetic Material A. 1865 Gregor Mendel —physical traits are inherited as discrete units B. 1928 Frederick Griffith —discovers a hereditary molecule that is transmissible between bacteria: “Transforming Principle” Polysaccharide capsule Streptococcuspneumoniae Conclusion: “Heat-killed Type S bacteria can transform live Type R bacteria into the virulent Type S form.”

  5. C. 1944 Avery, MacLeod, McCarty —treated heat-killed Type-S bacterial extracts prior to addition to live Type-R bacteria Treatment Transformation? Proteases Yes Lipases Yes DNase No RNase Yes Conclusion: “ The “transforming principle” is DNA

  6. D. 1951 Erwin Chargaff—DNA molecules Have Distinctive Base Compositions Conclusion: DNA has the characteristics expected of genetic material Purines/Pyrimidines (A+G/C+T) Chargaff’s rules: [A] = [T]; [G] = [C]; [purines] = [pyrimidines] A+G = C+T 1. The base composition of DNA varies from one species to another. 2. DNA specimens from different tissues of the same species have the same base composition. 3. The base composition doesn’t change with age, nutritional state, or changing environment. 4. In all cellular DNAs, regardless of species, the number of adenosine residues is the same as the number of thymidine residues and #guanosine=#cytosine residues.

  7. E. 1952 Hershey and Chase —”blender experiment” Proved that DNA is the hereditary molecule of bacteriophage DNA, not protein, enters bacterial cells and directs the synthesis of new viruses

  8. DNA is the Genetic Material of Living Cells Now what? Solve the 3D Structure of DNA

  9. Crystalline Paracrystalline Occurs at 75% rel. humidity Occurs at >75% rel. humidity Contains 30% water Contains >30% water Using X-ray Crystallography to Solve the Structure of DNA Two distinct forms of DNA exist: Structure A of DNA (Taken by Maurice Wilkins) Structure B of DNA (Taken by Rosalind Franklin) Natural DNA

  10. F. 1953—Watson and Crick Discover the Structure of DNA (Interpret X-ray data using molecular models)

  11. 1953—Watson and Crick propose a structure for DNA I. How DNA stores genetic information The sequence of the nucleotides encodes information about proteins II. How DNA is replicated Base complementarity: each strand serves as a template for a new strand

  12. II.Nucleotides Not very soluble Soluble Nitrogenous base Base + Ribose Nucleoside + phosphate 2’-deoxyribose

  13. The Common Nitrogenous Bases (Watson & Crick bases) Found in dsDNA RNA only DNA only

  14. Nomenclature of the nucleotides Base Nucleoside Nucleotide Nucleic Acid Purines RNA Adenine Adenosine Adenylate (Deoxyadenosine) (Deoxyadenylate) (DNA) Guanine Guanosine Guanylate (Deoxyguanosine) (Deoxyguanylate) Pyrimidines Cytosine Cytidine Cytidylate (Deoxycytidine) (Deoxycytidylate) Thymine (Thymidine) or (Deoxythmidine) (Thymidylate)or (Deoxythmidylate) Uracil Uridine Uridylate

  15. 5’ 4’ 1’ 3’ 2’ Nucleotides contain only the cyclic form D-ribose Ribose can exist in four different “puckered” conformations

  16. Nucleotides consist of: 1. a nitrogenous base 2. a ribose sugar 3. a phosphate group (or more) phosphoester bond N-glycosidic bond

  17. Nucleotides are formed by the removal of water phosphoester bond N-glycosidic bond

  18. Conformations of Bases when attached to Ribose Purines in syn or anti when attached to ribose (only anti in DNA) Pyrimidines only in anti when attached to ribose

  19. Nucleoside monophosphates (NMPs) can become NDPs and NTPs phosphoester bond phosphoanhydride bonds Hydrolysis of phosphoester14kJ/mol Hydrolysis of phosphoanhydrides30kJ/mol

  20. Functions of nucleotides Deoxyribonucleotides —dNTPs arebuilding blocks for making DNA Ribonucleotides —NTPs are building blocks for making RNA —ATP drives many reactions —GTP for protein synthesis (initiation and elongation) —CTP for lipid synthesis (CDP supplies the phosphate group in glycerophospholipids —UTP for carbohydrate metabolism (UDP-glucose + fructosesucrose) —Cyclic nucleotides (cAMP and cGMP) are signal molecules (epinephrine pathway)

  21. Unusual bases of RNA Inosine -can hydrogen bond w/ A, C, U -non W-C base-pairing”wobble”

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