Polymerase chain reaction (PCR)

Definition

A molecular technique that amplifies specific DNA sequences through repeated cycles of denaturation, primer annealing, and enzymatic extension, generating millions of copies from minute starting material. In arthropod research, PCR enables identification from degraded specimens, detection of pathogens in vectors, and phylogenetic analysis using mitochondrial or nuclear markers when morphological characters are ambiguous or life stages are cryptic.

Etymology

From 'polymerase,' the enzyme that synthesizes DNA polymers, and 'chain reaction,' describing the exponential amplification process.

Example

A field-collected mosquito damaged during transport can be identified to species by PCR amplification of the cytochrome oxidase I (COI) barcode region, even when diagnostic wing scales and leg ornamentation are missing.

Synonyms

• PCR

Related Terms

• DNA barcoding
• qPCR
• genomic DNA extraction
• primer
• amplicon
• Sanger sequencing
• molecular taxonomy
• vector surveillance

Usage Notes

The abbreviation PCR is nearly universal in scientific literature; spell out on first use in formal writing. Distinguish from qPCR (quantitative PCR, which measures starting copy number) and RT-PCR (reverse transcription PCR, which begins with RNA). In entomology, PCR is often coupled with Sanger sequencing or fragment analysis for species delimitation, though high-throughput amplicon sequencing is increasingly common for mixed samples such as pooled mosquitoes or gut contents.