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Structure of DNA

Structure of DNA. SBI 4U November 2 nd , 2012. Discovery of the Molecular Structure!. Fredrick Miescher : Disovered “ nuclein ” located within the nucleus of cells – today called nucleic acid

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Structure of DNA

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  1. Structure of DNA SBI 4U November 2nd, 2012

  2. Discovery of the Molecular Structure! • Fredrick Miescher: Disovered “nuclein” located within the nucleus of cells – today called nucleic acid • Scientists in 1940’s were aware of DNA being the molecule of life, but did not know what it looked like! • Franklin and Wilkins  used x-ray diffraction to study structure

  3. Discovery of the Molecular Structure … • Franklin’s famous x-ray diffraction photo allowed Watson & Crick to discover the double-helical structure of DNA

  4. The Basics • DNA is a polymer - polynucleotide • Nucleotides are the monomer units • Each nucleotide consists of: a deoxyribose sugar, a phosphate group and a nitrogeneous base • Source of variation  nitrogeneous bases

  5. 4 Bases in DNA • Adenine • Thymine • Guanine • Cytosine

  6. Purines & Pyrimidines • Two classes of nitrogen bases • Purine: Nitrogenous base with two-carbon nitrogen rings (Adenine & Guanine) • Pyrimidines: One carbon-nitrogen ring (Cytosine and Thymine)

  7. Basic Structure • Double-stranded helix • Ladder analogy • Sugar-phosphate backbone, bases in the middle

  8. Bonding between Molecules • Phosphate of one nucleotide bonded to the sugar of the next nucleotide – covalent bonding • Phosphodiester bond: A bond between 1 phosphate group and 2 sugar groups  link 2 nucleotides together

  9. Bonding Between Molecules, continued … • Hydrogen bonding: Between the phosphate groups and between the bases. Causes the DNA to adopt a “twist-like” stance

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