3.1.5. Nucelotides

• Nucleotides

  Pentose (5 Carbon Sugar), Nitrogen containing organic base, phosphate group.
• RNA transfers genetic information from DNA to ribosomes for protein synthesis.
• DNA has Adenine, Cytosine, Guanine and Thymine as bases.
• RNA has Adenine, Cytosine, Guanine and Uracil as bases
• Nucleotides join together by phosphodiester bond formed in condensation reactions.

  • Forms between deoxyribose sugar of one nucleotide and the phosphate group of another.
• DNA molecule

  Double helix

  • Two polynucleotides joined together by hydrogen bonds between specific complementary base pairs
• Ribosomes are formed from RNA and proteins
• An RNA molecule is a relatively short polynucleotide chain
• Semi-conservative replication of DNA ensures genetic continuity between generations of cells

  • One old, one new strand
• DNA replication

  • DNA helicase unwinds double helix; H bonds between complementary base pairs in the polynucleotide strands break
  • DNA strands act as templates
  • Free DNA nucleotide bases bond to exposed DNA nucleotides
  • Complementary base pairing
  • DNA polymerase joins nucleotides; condensation reaction of phosphodiester bonds
  • H bonds reform
• DNA and RNA are important information-carrying molecules
• DNA holds genetic information