DNA Replication

• Overview of DNA Replication

  • Semi-conservative replication - one strand is from the parental DNA and one strand is newly synthesised.
  • Process relies on the complimentary base pairs (cytosine + guanine, adenine + thymine).
  • Involves the enzymes DNA helicase and DNA polymerase.
  • Four key stages.
• Step 1 - DNA Replication

  • DNA helicase breaks the hydrogen bonds between the complimentary base pairs between the two strands within a double helix.
  • This causes the DNA double helix to unwind/unzip.
• Step 2 - DNA Replication

  • Each of the separated parental DNA strands acts as a template.
  • Free-floating DNA nucleotides within the nucleus are attracted to their complimentary base pairs on the template strands of the parental DNA.
• Step 3 - DNA Replication

  • The adjacent nucleotides are joined together, to form the phosphodiester bond, by condensation reaction.
  • DNA polymerase catalyses the joining together of adjacent nucleotides.
• Step 4 - DNA Replication

  • The two sets of daughter DNA contain one strand of the parental DNA and one newly synthesised.