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Topic 29Biology

D1.1 DNA replication

Semi-conservative DNA replication: the three candidate models and the Meselson-Stahl experiment; the four enzymes at the fork (helicase, primase, DNA polymerase, ligase) and leading-vs-lagging strand synthesis; AHL applications via PCR (DNA profiling, RT-PCR for COVID).

Practice questions
1

The semi-conservative modelSign up

Three candidate models (conservative, semi-conservative, dispersive) · Meselson-Stahl experiment (¹⁵N → ¹⁴N + CsCl gradient) · Why the band pattern uniquely supports semi-conservative

30 min
2

Enzymes of replicationSign up

Helicase, primase, DNA polymerase, ligase · Leading vs lagging strand and Okazaki fragments

30 min
3

PCR and replication biotechnology (AHL)HLSign up

PCR cycle (denature / anneal / extend) and Taq polymerase · DNA profiling (STRs) and RT-PCR for COVID-19

30 min

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D1.2 Protein synthesis