DNA Replication Leading and Lagging Strand Synthesis
These flashcards cover the distinct mechanisms of leading and lagging strand synthesis during DNA replication, essential for AP Biology, MCAT, and USMLE Step 1 preparation. Understanding why the lagging strand requires Okazaki fragments clarifies how the directional constraint of DNA polymerase shapes the entire replication process.
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5 CardsRole of primase in DNA replication
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What is the difference between leading and lagging strand synthesis?
The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized in short Okazaki fragments away from the fork.
- Leading: one primer, continuous extension
- Lagging: multiple primers, discontinuous Okazaki fragments
Why does DNA polymerase need an RNA primer to begin replication?
DNA polymerase can only add nucleotides to an existing 3'-OH group — it cannot initiate a new chain de novo. Primase provides a short RNA primer to create that starting point on both strands.
How many times does primase act on the lagging strand?
Primase acts once per Okazaki fragment, so it acts hundreds to thousands of times on the lagging strand per replication event. Each fragment needs its own RNA primer before DNA polymerase can extend it.