How do Conventional PCR work?
A thermal cycler holds reaction tubes or plates in a metal block whose temperature is controlled by Peltier thermoelectric elements. Each cycle denatures double-stranded DNA at about 94–98 °C, cools to the primer annealing temperature, typically 50–68 °C, and then heats to about 72 °C so a thermostable DNA polymerase extends the primers. Repeating this 25–40 times amplifies the target exponentially. Key components include the Peltier-driven block, a heat sink and fan, a temperature sensor feedback loop, a heated lid that prevents condensation and evaporation, and a controller that stores multi-step programs. Block uniformity and ramp rate determine how reproducibly each well reaches its set temperature.
Which Conventional PCR variants are available?
- 96-Well Standard Block Thermal Cycler — A 96-well standard block thermal cycler is the general-purpose PCR instrument, holding one 96-well plate or up to 96 tubes in a single Peltier-controlled block.
- Dual-Block Thermal Cycler — A dual-block thermal cycler contains two independently controlled blocks, usually 48 wells each or two 96-well blocks, so two different PCR programs run at the same time.
- Fast Thermal Cycler — A fast thermal cycler uses a low-mass block and high-power Peltier elements to reach ramp rates of 5–6 °C/s, cutting a 30-cycle run to 30–60 minutes.
- 384-Well Thermal Cycler — A 384-well thermal cycler holds a 384-well plate in one block, typically with reaction volumes of 5–20 µL, to multiply throughput and cut reagent use per reaction.
- Mini Portable Thermal Cycler — A mini portable thermal cycler is a compact 16–48 well unit that weighs a few kilograms, often with a built-in touchscreen and optional battery or vehicle power.
How do I choose the right variant?
Choose first by throughput and format: 96-well blocks suit most research work, 384-well blocks suit high-throughput screening, and small 16–48 well units suit teaching or occasional use. Next, compare ramp rate and block uniformity, because fast cyclers shorten run time but need polymerases and buffers validated for short steps. Dual-block instruments allow two independent programs at once and help shared core facilities. Check the heated lid range, programmable features such as touchdown and gradient, and whether the block is interchangeable. Consider connectivity for audit trails if the laboratory works under quality systems, and confirm the tube or plate formats you use, including low-profile plates and strip tubes.
Where are Conventional PCR used?
Conventional PCR are specified in gene cloning and plasmid construction, genotyping and mutation screening, pathogen detection by end-point PCR, colony PCR and insert verification and teaching laboratories.
Which standards and certifications apply?
Work with Conventional PCR is commonly governed by ISO 20395, ISO 22174, IEC 61010-1, IEC 61010-2-010, MIQE guidelines (research reporting) and CLSI MM19. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
Install the cycler on a stable bench with at least 10 cm of clearance for air intake and exhaust, away from direct sunlight and drafts. Verify block temperature accuracy and uniformity at installation and at least annually using a calibrated multi-point probe, and record results for audit. Clean the block wells with a lint-free swab and 70% ethanol to remove spilled reagent and prevent cross-contamination, and inspect the heated lid seal. Use sealing films or caps matched to the lid pressure. Keep pre-PCR and post-PCR work areas physically separated, and run no-template controls to detect amplicon carry-over. Firmware updates and program backups should be controlled under the laboratory's document system.
