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DNA Structure and Replication

DNA Structure and Replication. Chapter 16. A brief history…. Friedrich Miescher discovers nuclein by extracting white blood cells from pus-laden bandages: 1869. Frederick Griffith. NHS epidemiologist tried to find a pneumonia vaccine Found “transforming principle” instead.

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DNA Structure and Replication

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  1. DNA Structure and Replication Chapter 16

  2. A brief history… • Friedrich Miescher discovers nuclein by extracting white blood cells from pus-laden bandages: 1869

  3. Frederick Griffith • NHS epidemiologist tried to find a pneumonia vaccine • Found “transforming principle” instead

  4. Avery, McCarty, McLeod • Followed up on Griffith’s experiment • Demonstrated that DNA was Griffith’s “transforming principle”

  5. Hershey and Chase • Used phages to demonstrate that DNA was genetic material • Radiolabeled phages with 35S and 32P to distinguish protein from nucleic acid

  6. Erwin Chargaff • Devised nucleotide base pairing rules • Based on data that showed roughly equivalent percentages of adenine and thymine, cytosine and guanine • A-T; G-C pair up

  7. Franklin and Wilkins • Used x-ray diffraction to produce a photograph of DNA’s double helix structure

  8. Watson and Crick • Utilized data from multiple sources to deduce the structure of DNA • Won Nobel Prize with Wilkins, 1963

  9. Building Blocks of DNA • DNA is made of nucleotides: • 5-carbon sugar • Deoxyribose • Phosphate group • Nitrogen base

  10. Nitrogen Bases: Pyrimidines • Single ring structures: • Thymine • Cytosine

  11. Nitrogen Bases: Purines • Double ring structures: • Adenine • Guanine

  12. Base Pairing Rules Adenine pairs with thymine Guanine pairs with cytosine

  13. DNA Structure Hydrogen bonds hold the nitrogen bases across the center Phosphodiester bonds make up the sides of the helix

  14. Anti-parallel Structure • Sugar carbons are numbered 1’-5’ • One side of DNA runs in the 3’ direction • The other side runs in the 5’ direction • This is important to replication

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