Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A primer is a short single-stranded nucleic acid sequence that provides a starting point for DNA synthesis. It is essential for DNA polymerase to begin replication.
5 Must Know Facts For Your Next Test
A primer is typically composed of RNA in prokaryotic cells.
Primase is the enzyme responsible for synthesizing the primer.
The primer provides a free 3'-OH group necessary for DNA polymerase to add nucleotides.
Primers are removed and replaced with DNA nucleotides by DNA polymerase I during replication completion.
Without primers, DNA replication cannot initiate.
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Related terms
DNA Polymerase III: The enzyme that extends the primer by adding nucleotides during DNA synthesis.
Primase: The enzyme that synthesizes RNA primers needed to start DNA replication.
Okazaki Fragments: Short sequences of DNA nucleotides synthesized discontinuously and later linked together on the lagging strand during replication.