Asymmetric PCR

Definition

A polymerase chain reaction (PCR) modification that preferentially amplifies one DNA strand over its complement by using unequal primer concentrations, typically with one primer in limiting amount. The technique yields single-stranded DNA products useful for direct sequencing, hybridization probing, and preparing templates for downstream applications without strand separation.

Etymology

From Greek 'a-' (not) + 'symmetros' (symmetrical), describing the unequal primer ratio; PCR from polymerase chain reaction.

Example

In arachnological systematics, asymmetric PCR generates single-stranded mitochondrial COI templates from spider DNA extracts, enabling direct Sanger sequencing of the heavy strand without cloning or denaturing steps.

Synonyms

• asymmetric amplification
• unequal primer PCR

Related Terms

• PCR
• DNA barcoding
• Sanger sequencing
• single-stranded DNA
• primer
• mitochondrial DNA
• Phylogenetics

Usage Notes

Distinguished from standard PCR by its deliberate primer imbalance (typically 1:50 to 1:100 ratio). The technique becomes inefficient after 20–25 cycles as the limiting primer is exhausted; optimal yield requires empirical titration. Not suitable for quantitative applications. Often used in combination with biotinylated primers to facilitate strand purification.