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Analyzing real-time PCR data by the comparative CT method

Nature Protocols volume 3, pages 1101–1108 (2008)Cite this article

Abstract

Two different methods of presenting quantitative gene expression exist: absolute and relative quantification. Absolute quantification calculates the copy number of the gene usually by relating the PCR signal to a standard curve. Relative gene expression presents the data of the gene of interest relative to some calibrator or internal control gene. A widely used method to present relative gene expression is the comparative CT method also referred to as the 2 - ΔΔ C T method. This protocol provides an overview of the comparative CT method for quantitative gene expression studies. Also presented here are various examples to present quantitative gene expression data using this method.

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Figure 1: Real-time PCR output, calculation of CT.
Figure 2: Real-time PCR plots from gene expression profiling.
Figure 3: Real-time PCR expression profiling of microRNA in pancreas tissue.

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Authors and Affiliations

  1. Division of Pharmaceutics, College of Pharmacy, Ohio State University, Parks Hall, 500 West 12th Avenue, Columbus, OH 43210, Ohio, USA

    Thomas D Schmittgen

  2. Applied Biosystems, 850 Lincoln Center Drive, Foster City, CA 94404, California, USA

    Kenneth J Livak

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  1. Thomas D Schmittgen
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  2. Kenneth J Livak
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Correspondence to Thomas D Schmittgen.

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Schmittgen, T., Livak, K. Analyzing real-time PCR data by the comparative CT method. Nat Protoc 3, 1101–1108 (2008). https://doi.org/10.1038/nprot.2008.73

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