Primer

Definition

A primer is a short strand of RNA or DNA that serves as a starting point for DNA synthesis. Primers are necessary because DNA polymerases can only add new nucleotides to an existing strand of DNA.

5 Must Know Facts For Your Next Test

1. Primers are usually around 18-22 bases in length.
2. They are synthesized by the enzyme primase during DNA replication.
3. Primers provide the free 3' hydroxyl group needed for DNA polymerase to initiate synthesis.
4. In PCR (polymerase chain reaction), primers are designed to flank the target sequence of interest.
5. After their function is served, primers are removed and replaced with DNA nucleotides.

Review Questions

• Why are primers essential for DNA polymerase during replication?
• What enzyme synthesizes RNA primers in prokaryotic cells?
• How do primers function in PCR techniques?

Related terms

DNA Polymerase: An enzyme that synthesizes new strands of DNA complementary to the template strand.

Primase: An enzyme that synthesizes short RNA sequences called primers.

PCR (Polymerase Chain Reaction): A technique used to amplify small segments of DNA using cycles of denaturation, annealing, and extension.