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Molecular Biology of the Gene

Molecular Biology of the Gene. DNA. Identification of Genetic Material Structure of DNA DNA Replication. Genetic Material –DNA or Protein?. Bacteriophage Replication. Martha Chase and Alfred Hershey (1952). Roles of the Genetic Material.

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Molecular Biology of the Gene

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  1. Molecular Biology of the Gene DNA

  2. Identification of Genetic Material • Structure of DNA • DNA Replication

  3. Genetic Material –DNA or Protein? Bacteriophage Replication Martha Chase and Alfred Hershey (1952)

  4. Roles of the Genetic Material “A 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

  5. Hershey and Chase Experiment

  6. Bacterial Transformation Frederick Griffith, 1928 • Diplococcus pneumoniae infects mice • Mice develop pneumonia and die Two types of bacteria: • R bacteria rough coat  no pneumonia • S bacteria smooth coat  pneumonia • Coat type is associated with virulence.

  7. Griffith’s Experiments Figure 9.1

  8. The “Transforming Principle” • Avery, MacLeod, and McCarty, 1944 • Treated lysed S bacteria with protease and DNase • DNase prevented transformation • Therefore DNA is the transforming principle Figure 9.2

  9. Monomers and Polymers • Polymers are made up of monomers • Mono = one • Poly = many • For example: Proteins are made up of amino acids

  10. Polynucleotides • Polynucleotides are made up of nucleotides Sugar-phosphate backbone Phosphate group A Nitrogenous base A Sugar Nitrogenous base (A, G, C, or T) C C Phosphate group DNA nucleotide T T Thymine (T) G G Sugar (deoxyribose) T T DNA nucleotide DNA polynucleotide

  11. Basic Structure of a Nucleotide Phosphate Group Nitrogenous Base Sugar

  12. Nitrogenous Bases (DNA) Cytosine (C) Adenine (A) Guanine (G) Thymine (T) Purines Two Rings PyrimidinesOne Ring

  13. And the Nobel Prize Goes To… • Physiology or Medicine 1962"for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material" Rosalind Franklin (1920-1958) Watson and Crick with their model of DNA

  14. Rope Ladder Model

  15. Rope Ladder Model Sugar and Phosphate Backbone Nitrogenous Base Pairs

  16. Complementary Base Pairs • A-T • G-C

  17. DNA: The Double Helix C G T A Hydrogen bond T A Base pair T A G C G C G C A T C G C G T A A T A T T A T A G C A T Computer model Ribbon model Partial chemical structure

  18. Orientation of DNA The 5’ phosphate of one nucleotide is attached to the 3’ hydroxyl group of the previous nucleotide The directionality of a DNA strand is due to the orientation of the phosphate-sugar backbone Figure 9.11

  19. Structure of DNA • DNA Replication • DNA vs. RNA

  20. Chromosomes and Mitosis

  21. Chromosomes Are Made of DNA

  22. T A T A T T T A A A C G C G C G C G G C G C G C G C G C C A T A T T T A A A A T A T T T A A Nucleotides Parental molecule of DNA Both parental strands serve as templates Two identical daughter molecules of DNA DNA Replication • DNA Replication is Semiconservative Each new double helix contains one parental strand and one daughter strand

  23. G C A T G C C G A T T A G C A T C G G C C G G C C C G A C A G T A T T G T T G T A A T A A A T C A T T A

  24. An enzyme “unzips” DNA Replication Bubble

  25. Parental strand Origin of replication Daughter strand Bubble Two daughter DNA molecules Replication Bubbles

  26. 3 end 5 end P HO 5¢ 2¢ 4¢ 3¢ A T 3¢ 1¢ 1¢ 4¢ 2¢ 5¢ P P P C G P P C G P P T A OH P 3 end 5 end One Little Problem… DNA is synthesized from 5’ to 3’

  27. DNApolymerase molecule 3¢ 5¢ LEADING STRAND Daughter strand synthesized continuously Parental DNA 5¢ 3¢ LAGGING STRAND Daughter strand synthesized In pieces 3¢ 5¢ DNA Polymerase Can Only Move 5’ to 3’ DNA polymerase adds nucleotides to the 3’ end “ase” = enzyme

  28. 5¢ 5¢ 3¢ 3¢ DNA ligase DNA Ligase LEADING STRAND LAGGING STRAND DNA ligase “glues” the fragments together

  29. Structure of DNA • DNA Replication • DNA vs. RNA

  30. H Uracil (U) Nitrogenous Bases (DNA and RNA) Cytosine (C) Adenine (A) Guanine (G) Thymine (T) Purines Two Rings PyrimidinesOne Ring

  31. Nitrogenous Bases U C A G DNA vs. RNA Ribonucleic Acid Deoxyribonucleic Acid Nitrogenous Base Phosphate Group Nitrogenous Base Phosphate Group H CH3 Uracil Thymine Deoxyribose Ribose OH H Nitrogenous Bases T C A G

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