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Biology · Quick Reference
Lesson 12 — DNA Structure & Replication Cheat Sheet
In one line: A = T (2 H-bonds), G ≡ C (3 H-bonds); helicase unwinds, polymerase synthesises, ligase joins — result: 2 identical DNA molecules.
Key Ideas
1Structure. Antiparallel double helix (Watson & Crick, 1953).
2Base pairing. A=T (2 H-bonds), G≡C (3 H-bonds).
3Semi-conservative. Each new molecule = 1 old strand + 1 new strand.
4Leading vs lagging. Leading = continuous; lagging = Okazaki fragments.
5Central dogma. DNA → mRNA → Protein.
Replication Enzymes
Helicase
Unwinds the double helix
Primase
Adds RNA primer
DNA polymerase III
Adds nucleotides 5'→3'
Ligase
Joins Okazaki fragments