STRUCTURE OF RNA & DNA

• Nucleotide structure

  Contains:

  • pentose sugar (ribose in RNA and deoxyribose in DNA)
  • phosphate group
  • nitrogenous organic base (A, T (U in RNA), C, G)
• What reaction joins a pentose sugar, phosphate group and organic base?


  Condensation reaction
• What reaction joins two nucleotides?

  Condensation reaction between deoxyribose sugar and phosphate group- forms a phosphodiester bond.
• RNA structure

  Ribonucleic acid

  • polymer made of nucleotides
  • single, quite short polynucleotide chain
  • ribose sugar
  • U instead of T
• DNA structure

  Deoxyribonucleic acid

  • two extremely long strands of polynucleotides
  • strands joined together by H bonds
  • double helix
• What word describes base pairing?

  Complementary
• How many H bonds between C and G?

  3
• How many H bonds between A and T?


  2
• Why is DNA a stable molecule?

  Because:

  • phosphodiester backbone protects chemically reactive bases inside double helix
  • H bonds link organic base pairs to form bridges between the pairs (the higher proportion of C-G the more stable)
• Function of DNA

  Hereditary material responsible for passing genetic information from cell to cell and generation to generation
• How is DNA adapted to carry out its functions?

  Adaptations:

  • stability so DNA remains unchanged to pass from generation to generation (mutations are rare)
  • 2 separate strands joined by H bonds allowing them to separate during DNA replication and protein synthesis
  • extremely large molecule to carry an immense amount of genetic information
  • phosphodiester backbone protects inner bases from being corrupted
  • base pairing means DNA is able to replicate and transfer information as mRNA