Nucleic Acids

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  • Nucleic Acids
    • Nucleotides
      • consists of a pentose sugar, phosphate group and organic bases
      • a condensation reaction joins two nucleotides
        • forms a dinucleotide
        • bond formed between the pentose sugar and phosphate group
          • phosphodiester bond
      • joining of multiple nucleotides by condensation reaction
        • forms polynucleotide
      • ester bond between pentose sugar and phosphate
      • glyosidic bond between bases and pentose sugar
    • DNA
      • made of deoxyribose sugar, phosphate group and 4 different organic bases
      • double helix structure
      • stability
        • phosphodiester backbone protects the reactive organic bases
        • higher the proportion of C - G the more stable
      • four different bases are adenine, thymine, guanine and adenine
        • A always pairs with T
          • 2 hydrogen bond
        • G always pairs with C
          • 3 hydrogen bonds
        • A and G are purines (two carbon nitrogen rings)
        • T and C are pyrimidines (single carbon nitrogen ring)
      • adaptations to carry out function
        • DNA is stable
          • rarely mutates
        • two separate strands only joined by hydrogen bonds
          • which allows them to be separated during replication
        • large molecule
          • can carry large amounts of genetic infromation
        • bases protected by the backbone
          • genetic info is protected from being corrupted
    • Semi Conservative Replication
      • Requirements
        • 4 nucleotides with 4 bases A G C T
        • both strands of DNA to act as a template
        • source of chemical energy
        • enzyme DNA polymerase
      • Process
        • 1.) enzyme DNA helicase breaks hydrogen bonds between bases causing DNA strands to separate
        • 2.) each exposed polynucleotide acts a template where free activated nucleotides bind to their complementary bases
        • 3.) nucleotides join in condensation reaction by the enzyme DNA polymerase to form a new polynucleotide strand
        • 4.) any remaining nucleotides continue to pair
        • 2 identical DNA molecules are formed with 1 original strand and 1 new. 50% of DNA is saved
    • RNA
      • single short chain
      • made up of a ribose sugar phosphate group and organic base
      • has the bases adenine guanine cytosine and uracil
      • RNA types
        • mRNA
          • transfers genetic info
        • rRNA
        • tRNA
          • used in protein synthesis


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