thermocyclers

Thermocyclers, also called PCR machines, are laboratory instruments that amplify DNA or RNA by polymerase chain reaction. They enable rapid cycling of samples through programmed temperatures to denature, anneal primers, and extend DNA strands, generating millions of copies of a target sequence.

A typical instrument contains a thermal block or blocks heated by Peltier elements, a heated lid to prevent condensation, and a control system that follows a user-defined cycling protocol. The cycle usually includes denaturation around 95 C, annealing around 50–65 C, and extension around 72 C, though exact temperatures depend on primers and polymerase. Real-time machines integrate optical modules to monitor fluorescence during amplification and quantify products in real time.

There are several variants: conventional end-point thermocyclers perform amplification with end-point analysis; gradient thermocyclers allow testing of temperature settings across a block to optimize conditions; real-time or quantitative PCR (qPCR) instruments measure signal during cycling for quantitation; portable and benchtop models vary in throughput (e.g., 16, 24, 96, or 384 wells).

Applications include clinical diagnostics, pathogen detection, genetic testing, cloning and mutation analysis, forensic genetics, and basic research. PCR, developed by Kary Mullis in 1983, enabled the creation of thermocyclers and automated cycling processes that are central to modern molecular biology.

Key performance characteristics include temperature uniformity across wells, ramp rate (how quickly temperatures change), block design, and software for data analysis and experiment management. Maintenance requirements include regular calibration and contamination control.