Which technique is used to rapidly amplify DNA for microbial identification?

• A. Mass spectrometry
• B. Gel electrophoresis
• C. Polymerase chain reaction (PCR)
• D. Northern blotting

Answer: (C)

The technique tested is about rapidly increasing the amount of a specific DNA sequence so microbes can be identified from small samples. PCR does this by using short primers that flank the target DNA and a heat-stable DNA polymerase to copy the sequence through many cycles of denaturation, annealing, and extension. With each cycle, the target DNA is amplified exponentially, so a tiny starting amount becomes millions of copies in a short time. This makes it possible to detect and identify microbes quickly, even directly from clinical specimens, and real-time PCR variants can provide results as amplification proceeds.

Other methods don’t amplify DNA. Mass spectrometry identifies organisms by measuring the mass of biomolecules rather than creating new DNA copies. Gel electrophoresis separates amplified DNA fragments to reveal their sizes but does not amplify DNA by itself. Northern blotting detects RNA rather than DNA and requires additional steps, not rapid DNA amplification.