Which of the following is NOT considered a significant advance in PCR methodology?

The invention of the thermal cycler

The use of reverse transcriptase to generate cDNA from single-stranded RNA

The use of agarose gel electrophoresis to visualize amplified products

The use of fluorescently-tagged probes for real-time quantitation of PCR

The use of agarose gel electrophoresis to visualize amplified products

DNA ligase:

Joining pieces of DNA together

Performing PCR reactions

Digesting DNA

Degrading protein

Joining pieces of DNA together