Which device rapidly changes sample temperatures and is used for polymerase chain reaction (PCR)?

• A. Centrifuge
• B. Thermocycler
• C. Spectrophotometer
• D. Chromatography

Answer: (B)

PCR relies on rapid, precise temperature changes to denature DNA, allow primers to bind, and extend new DNA strands through repeated cycles. A thermocycler is designed to do exactly that, with programmable heating and cooling that quickly shifts to the required temperatures and maintains tight control throughout many cycles. It often includes features like a heated lid to prevent evaporation, making it ideal for PCR. Other instruments don’t perform this rapid thermal cycling: a centrifuge spins samples but doesn’t change their temperature, a spectrophotometer measures light absorption to quantify nucleic acids, and chromatography separates compounds.