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  • Created by: emma
  • Created on: 09-04-14 15:09
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  • DNA
    • Nucleic acid
      • Monomer Nucleotide, polymer nucleic acid
      • Nucleotide
        • Made up of phosphate group, organic base, pentose sugar
      • DNA is a type of nucleic acid
        • Made up of phosphate group, organic base, deoxyribose sugar
      • Many nucleotides link to make a nucleic acid (sugar phosphate link)
        • This is a covalent bond and makes the back bone strong and stable
    • Structure
      • Two parallel nucleotide strands held together by hydrogen bonding
        • Between organic bases
          • Adenine and Thymine
          • Cytosine and Guanine
        • To make sure they are parallel a 2 ring base must bond with a 1 ring base
        • Two strands fold into a helix
    • Triplet code and genes
      • Every three bases code for an amino acid (codon)
        • A change on base sequences could lead to a non functioning enzyme
          • DNA base sequence codes for amino acid sequence
            • Chaning hydrogen, ionic and disulphide bonds between R groups
              • Leading to a change in tertiary structure/ shape of active site
      • A gene is the section of DNA that codes for a particular polypeptide
        • The different forms of the same gene are alleles
    • Non coding DNA
      • Dont code for polypeptides
      • Within genes there are introns
    • Replication
      • DNA helicase breaks hydrogen bonds between complementary bases
        • strands separate
          • Individual DNA nucleotides base pair with exposed bases
            • DNA polymerase connects new nucleotides forming sugar phosphate links
              • Semi conservative
    • Experiments
      • Hersey and Chase
        • radioactive S35 labeled proteins in phages (S found in protein but not DNA)
          • No radioactive S was found in next generation of phages
            • Radioactive P32 labeled DNA in phages (P found in DNA but not protein)
      • Griffiths
        • Mouse injected with safe strain and survives
          • Mouse injected with harmful strain and dies
            • Mouse injected with harmful heat killed strain suvrives
              • Mouse injected with safe strain and harmful heat strain dies


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