DNA Replication

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•  Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds

•  DNA polymerase links nucleotides together to form a new strand, using the pre-existing strand as a template

DNA replication is a semi-conservative process whereby pre-existing strands act as templates for newly synthesised strands

The process of DNA replication is coordinated by two key enzymes – helicase and DNA polymerase


  • Helicase unwinds the double helix and separates the two polynucleotide strands
  • It does this by breaking the hydrogen bonds that exist between complementary base pairs
  • The two separated polynucleotide strands will act as templates for the synthesis of new complementary strands

DNA Polymerase

  • DNA polymerase synthesises new strands from the two parental template strands
  • Free deoxynucleoside triphosphates (nucleotides with 3 phosphate groups) align opposite their complementary base partner
  • DNA polymerase cleaves the two excess phosphates and uses the energy released to link the nucleotide to the new strand

DNA Replication Summary

DNA replication

DNA Replication Animation