A-Level Biology AQA Notes

3.1.5.2 DNA replication

DNA Double Helix & Replication
  • Polynucleotides are polymers made up of many nucleotide monomers joined together by a series of condensation reactions, forming phosphodiester bonds.
  • The DNA double helix is held together by hydrogen (H) bonds between complementary base pairs.
    • 2 H bonds between Adenine & Thymine
    • 3 H bonds between Cysteine and Guanine
  • Semi conservative replication is the method in which DNA replicates, creating two molecules of DNA that consist of one original DNA strand and one newly synthesised DNA strand.
    • DNA helicase breaks H bonds between the two strands
    • Free nucleotides complementary base pair to the exposed strands
    • ​DNA polymerase catalyses condensation reactions to join adjacent nucleotides, forming phosphodiester bonds.
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