Primer (molecular biology)

A primer in molecular biology is a short nucleic acid sequence that provides a starting point for DNA synthesis. In living organisms, primers are short strands of RNA. Most primers are synthetically produced and are used in the laboratory for DNA amplification and DNA sequencing.

Function

Primers are necessary for DNA replication because the enzymes that catalyze this process, DNA polymerases, can only add new nucleotides to an existing strand of DNA. The primer therefore serves to prime and define the start of DNA synthesis.

Types of Primers

There are two types of primers: forward and reverse. The forward primer binds to the start of the region of DNA to be amplified or sequenced, and the reverse primer binds to the end of the region.

Use in Polymerase Chain Reaction

Primers are crucial in the PCR technique. In PCR, a pair of primers is used to hybridize with the ends of the DNA region to be amplified, and DNA polymerase extends the primers to form a copy of the DNA region.

Use in DNA Sequencing

In DNA sequencing, a primer is used to initiate the synthesis of the new DNA strand. The primer binds to the DNA template, and DNA polymerase extends the primer, incorporating fluorescently labeled nucleotides into the new DNA strand.

See Also

• Polymerase Chain Reaction
• DNA sequencing
• DNA polymerase
• Nucleic acid

External Links

• Primer (molecular biology) at NCBI

• Primer (molecular biology)
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  DNA replication diagram
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  Primers and reverse complement