Nucleic Acids

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  • Created by: R214116
  • Created on: 02-03-20 09:06
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  • Nucleic Acids
    • DNA
      • Structure
        • Nucleotides
          • A pentose sugar - deoxyribose
          • A phosphate group
            • 5'
          • A nitrogenous base
            • Pyrimidines
              • Single C ring
                • T and C
            • Purines
              • Double C ring
                • A and G
            • A forms 2H bonds with T
            • G forms 3H bonds with C
          • Phosphodiester bonds
            • Phosphate on 5' and OH on 3'
        • Antiparallel
        • Double helix
      • Replication
        • Semi-conservative replication
          • 1. DNA helicase separates strands
          • 2. Free nucleotides attracted to complementary bases
          • 3. Once lined up, nucleotides joined by DNA Polymerase
          • New DNA has one parent strand, one new strand
          • Discontinuous Replication
            • Unzipped from 5'
          • Continuous replication
            • Unzipped from 3'
          • Evidence
            • 1. Meselson and Stahl grew E.coli on medium with N15
            • 2. Transferred to N14 for 1, 2 or 3 gens
            • 3. Density centrifrugation
            • 4. UV light
            • RESULT -  density decreased
        • Conservative replication
          • Completely new double stranded DNA made
          • Parent DNA remains the same
      • Triplet code
        • 3 base pairs are a codon
          • Code for one AA
          • A set of codons create a gene
        • Introns
        • Degenerate code
          • 64 combinations, only 20 AAs
        • Methionine
          • Non overlapping
        • Stop codons
          • Non overlapping
    • RNA
      • Nucleotides
        • Phosphate group
        • A pentose sugar - ribose
        • A nitrogenous base
          • T replaced with U
    • Protein Synthesis
      • Transcription
        • 1. DNA helicase unwinds DNA
        • 2. Free RNA nucleotides complementary base pair
          • Antisense strand 3'-5'
        • 3. RNA polymerase catalyses phosphodiester bonds
        • 4. At stop codon, transcription stops - mRNA formed
        • 5. mRNA detaches from antisense and exits
        • 6. Double helix reforms
          • DNA polymerase
      • Translation
        • Ribosomes
          • Large and small subunit
          • Composed of protein and rRNA
          • rRNA maintains structure and catalyses reactions
        • tRNA
          • One RNA strand folded
          • Anticodon
            • Complementary to a codon
          • Carries AA that anticodon is complementary to
        • 1. mRNA binds to small subunit of DNA at start codon
        • 2. tRNA with complementary anticodon binds to mRNA start codon
        • 3. tRNA lines up with next codon
        • 4. Peptidyl transferase catalyses peptide bond between AAs
        • 5. tRNA detaches and ribosome moves along strand until a stop codon

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