PolydG is added to the terminal overhangs of an siRNA. Next, a primer containing a polydC sequence added with a tag sequence is annealed and cDNA is synthesized by a reverse transcription reaction. Quantitative PCR is performed between a primer carrying the same sequence as the tag sequence, and a primer containing the same sequence as the siRNA sequence to be detected. The amount of siRNA of interest can be determined from a calibration curve produced using knows amounts of short-chain dsDNA.
