Real-time PCR development was driven by which property of Taq polymerase?

Real-time PCR development was driven by which property of Taq polymerase?

• A. 5′-to-3′ exonuclease activity
• B. 3′-to-5′ exonuclease activity
• C. High thermostability
• D. Ability to be incorporated into plasmids

Answer: (A)

Real-time PCR relies on detecting DNA synthesis as it happens by using a probe that is cleaved during amplification. In the typical TaqMan approach, a reporter dye on the probe is kept quenched until the polymerase removes the probe through its 5′-to-3′ exonuclease activity. As the polymerase extends the primer, it degrades the probe in front of it, separating the reporter from the quencher and generating a fluorescent signal. This signal increases with each cycle and directly reflects the amount of amplified product, enabling real-time quantification. The ability to cleave the probe in the 5′-to-3′ direction is the essential feature that enables this real-time detection. Thermostability helps the enzyme survive the cycling temperatures, but it does not by itself produce the real-time signal. The 3′-to-5′ exonuclease proofreading activity would not enable probe cleavage, so it wouldn’t drive the real-time detection. Incorporation into plasmids is unrelated to how the real-time signal is generated.

Real-time PCR relies on detecting DNA synthesis as it happens by using a probe that is cleaved during amplification. In the typical TaqMan approach, a reporter dye on the probe is kept quenched until the polymerase removes the probe through its 5′-to-3′ exonuclease activity. As the polymerase extends the primer, it degrades the probe in front of it, separating the reporter from the quencher and generating a fluorescent signal. This signal increases with each cycle and directly reflects the amount of amplified product, enabling real-time quantification. The ability to cleave the probe in the 5′-to-3′ direction is the essential feature that enables this real-time detection. Thermostability helps the enzyme survive the cycling temperatures, but it does not by itself produce the real-time signal. The 3′-to-5′ exonuclease proofreading activity would not enable probe cleavage, so it wouldn’t drive the real-time detection. Incorporation into plasmids is unrelated to how the real-time signal is generated.