Which PCR method provides real-time quantification of product accumulation?

• A. Endpoint PCR
• B. RT-PCR
• C. qPCR
• D. Southern blot

Answer: (C)

Real-time quantification hinges on watching PCR amplification as it happens. In qPCR, fluorescence increases during each cycle as more product is formed, providing a live readout of the reaction. The point where the signal crosses a set threshold (the Ct value) correlates with how much starting template was present, allowing precise quantification without running separate gels or dishes. Endpoint PCR, by contrast, only analyzes the final amount of product after all cycles are complete, so it can’t track accumulation in real time and is less reliable for comparing initial template amounts. RT-PCR refers to reverse transcription followed by amplification; unless it’s the real-time variant (RT-qPCR), it doesn’t inherently provide real-time quantification. Southern blot is a hybridization technique for detecting specific DNA fragments and doesn’t involve real-time amplification. So the method that provides real-time quantification of product accumulation is qPCR.