Pcr machine running cycle

The PCR machine performs thermal cycles to amplify DNA, essential in diagnostics and genetic research.

About this subject

Polymerase chain reaction (PCR) is a molecular biology technique that amplifies millions of copies of a specific DNA segment. The PCR machine, or thermocycler, performs repeated cycles of controlled temperatures: denaturation at about 95°C, annealing of primers between 50-65°C, and extension at 72°C. Each cycle doubles the target DNA amount, reaching billions of copies after 30 to 40 cycles.

PCR became indispensable in medical diagnostics, especially for detecting infectious diseases like COVID-19, where RT-PCR tests are the gold standard. It is also used in genetic testing, forensic identification, mutation research, and DNA sequencing. The technique was invented by Kary Mullis in 1983, earning him the Nobel Prize in Chemistry in 1993.

Modern thermocyclers feature metal thermal blocks with holes for tubes or plates, heated by Peltier elements, enabling rapid and precise temperature changes. A heated lid prevents condensation on tube tops. Some models include a thermal gradient, testing multiple annealing temperatures simultaneously.

Beyond conventional PCR, variants include real-time PCR (qPCR), which quantifies DNA in real time using fluorescence, and digital PCR, providing absolute quantification. These advances expand the technique's applications in rapid diagnostics and genomic research.

Frequently Asked Questions

What is PCR and how does it work?

PCR (Polymerase Chain Reaction) is a technique that amplifies DNA through thermal cycles: denaturation, annealing, and extension. A PCR machine controls these temperatures to repeatedly copy the target segment.

How many cycles are needed in a typical PCR?

A typical PCR runs 30 to 40 cycles. After 30 cycles, over one billion copies of the target DNA can be obtained.

What is PCR used for in medicine?

PCR is used to diagnose infectious diseases (like COVID-19, HIV, hepatitis), identify genetic mutations, detect pathogens in clinical samples, and in forensic testing.