Relative quantification for construction of standard curve of gene specific primed cDNA for calculation of the preamplification efficiency, by taking r2 (R square) value. Used standard dilutions of non-preamplified cDNA were 25 ng/μL, 2.5 ng/μL, 0.25 ng/μL, 0.025 ng/μL, 0.0025 ng/μL. Preamplified unknown cDNA sample volume was corresponding to the volume of 2.5 ng/μL standard dilution. A) RNA extraction method A; B) RNA extraction method B. Legend: standard dilutions (●); unknown sample (♦).