A-LEVEL BIOLOGY AQA NOTES
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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.