DNA & RNA Structure

• A nucleotide is made up of a phosphate group, a pentose sugar (ribosomes in RNA, deoxyribose in DNA), a nitrogenous base
• Nitrogenous Bases:

  • Purine bases - has 2 rings: adenine, guanine (Pure As Gold)
  • Pyrimidine Bases- has 1 ring: cytosine, uracil (RNA only), thymine (DNA only)
• Nucleotides are joined by phosphodiester bonds during a condensation reaction
• RNA:

  • ribonucleic acid
  • single-stranded
  • ribose sugar
  • uracil present
  • no complementary bases pairing
  • ratio of A+G to C+U is variable
  • three types - mRNA, tRNA, rRNA
  • shorter
• DNA:

  • deoxyribonucleic acid
  • double-stranded
  • deoxyribose sugar
  • thymine present
  • complementary base pairing along whole molecule
  • ratio of A+G to C+T is 1
  • only one type
  • longer
• Complementary bases pairing:

  • 2 H bonds between A and T
  • 3 H bonds between G and C (God Christ, 3 - God, Christ, Holy Spirit)
  • easily broken for transcription to RNA or replication
• Structural characteristics of DNA:

  • two strands of polynucleotides are antiparallel
  • one strand runs from the 5' to 3' direction
  • the other runs from 3' to 5'