Which statement best describes qPCR compared with standard PCR?

Which statement best describes qPCR compared with standard PCR?

• A. qPCR measures DNA quantity only at the end of amplification.
• B. qPCR quantifies DNA in real time using fluorescence; standard PCR measures end-point product.
• C. qPCR requires RNA templates.
• D. qPCR does not use a DNA polymerase.

Answer: (B)

Real-time monitoring of DNA during amplification is what sets qPCR apart. In qPCR, the reaction includes a fluorescent signal that increases as more double-stranded DNA is made. By watching this fluorescence cycle by cycle, you can quantify how much template you started with, because the moment the signal passes a chosen threshold correlates with the initial amount. This gives data across a wide range of quantities and can be used for precise absolute or relative quantification.

Conventional PCR, on the other hand, is detected only after amplification ends. The common readout is an end-point product, often checked by gel, which doesn’t track how the amount of DNA changed during the cycles and is much less reliable for quantification because the reaction reaches a plateau and varies in efficiency between samples.

RNA templates aren’t a requirement for qPCR itself—if you start from RNA, you use RT-qPCR to convert it to cDNA first; the core idea remains real-time fluorescence during amplification. And both methods rely on DNA polymerase to copy DNA, so that aspect isn’t a distinguishing feature.