Primer

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

1. A primer is typically composed of RNA in prokaryotic cells.
2. Primase is the enzyme responsible for synthesizing the primer.
3. The primer provides a free 3'-OH group necessary for DNA polymerase to add nucleotides.
4. Primers are removed and replaced with DNA nucleotides by DNA polymerase I during replication completion.
5. Without primers, DNA replication cannot initiate.

Review Questions

• What role does a primer play in DNA replication?
• Which enzyme synthesizes the primer in prokaryotes?
• Why is the 3'-OH group on a primer crucial for DNA polymerase function?

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.