How do PCR work?
PCR copies a target sequence with a thermostable DNA polymerase such as Taq, two primers that flank the target, deoxynucleoside triphosphates and a buffer. A thermal block cycles the reaction from about 95 °C, where double-stranded DNA separates, to 50 to 65 °C for primer annealing, then 72 °C for extension. Repeating 25 to 45 cycles doubles the product each round, so amplification is exponential while reagents last. Endpoint cyclers read the product afterwards on a gel or capillary system, while real-time instruments measure fluorescence each cycle using an intercalating dye or a hydrolysis probe, and the cycle threshold reflects the starting template amount. Quantitative results need a standard curve or reference gene, and melting curve analysis checks product specificity or detects sequence variants by high-resolution melting. Reverse transcription adds a step for RNA targets.
Which PCR variants are available?
- Endpoint PCR Thermal Cycler — A thermal cycler that runs amplification and leaves the product for later analysis by gel or capillary electrophoresis.
- Real-Time Quantitative PCR System — A 96-well instrument that measures fluorescence during each cycle to quantify target nucleic acid without opening the tube.
- High-Resolution Melt PCR Analysis System — A real-time PCR platform with precise thermal control and saturating fluorescent dyes that resolves small melting temperature differences, allowing small sequence variants and genotypes to be distinguished without labelled probes or DNA sequencing.
- Multiplex PCR System for Pathogen Panel Detection — A real-time PCR instrument configured with four to six optical channels, panel software and validated reagent workflows to detect several pathogens in one reaction.
- Portable Field PCR System — A compact, low-power thermal cycler or real-time instrument with a small block, rugged case and battery or 12 V supply.
How do I choose the right variant?
Decide first whether you need qualitative detection, relative or absolute quantification, or sequence variant discrimination, because that separates endpoint cyclers from real-time and melt systems. Next, set the number of optical channels, since multiplex panels need two to six channels and matching filter sets. Throughput follows the plate format: 96 wells suits most laboratories, while 384-well plates and automation fit high-volume screening. Check block type, maximum ramp rate, temperature uniformity and gradient capability, which help with new primer sets. For field work, consider size, power options and tolerance of ambient temperature. Confirm analysis software, export formats, primer and probe support, and the validation documentation your quality system requires.
Where are PCR used?
PCR are specified in gene expression analysis and transcript quantification, pathogen detection in clinical and food samples, genotyping and mutation screening, template preparation for cloning and sequencing and agricultural and environmental DNA testing.
Which standards and certifications apply?
Work with PCR is commonly governed by ISO 13485 manufacturing, MIQE guidelines, CLSI MM03-A2, CLSI MM06-A2, IEC 61010-1 and IVDR (EU) 2017/746. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
Keep pre-amplification and post-amplification work in separate areas with dedicated pipettes and filter tips, because carryover of amplicon is the main cause of false positives. Clean surfaces and equipment with fresh hypochlorite or a validated decontaminant, use UV where available and change gloves often. Calibrate block temperature and optical channels annually with a reference thermometer and dye plate, and check uniformity across the block. Verify performance with positive and negative controls and a standard curve in every run, and record Ct, efficiency and melt temperatures. Store primers and probes in small aliquots at the recommended temperature to avoid repeated freeze-thaw cycles, and protect fluorescent probes from light.
