Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as rRNA genes or tRNA genes, the product is a structural or housekeeping RNA. In addition, small non-coding RNAs (miRNAs, piRNA) and various classes of long non-coding RNAs are involved in a variety of regulatory functions.

When studying gene expression with real-time polymerase chain reaction (PCR), scientists usually investigate changes—increases or decreases—in the expression of a particular gene or set of genes by measuring the abundance of the gene-specific transcript. The investigation monitors the response of a gene to treatment with a compound or drug of interest, under a defined set of conditions. Gene expression studies can also involve looking at profiles or patterns of expression of several genes.

Gene expression profiling simultaneously compares the expression levels of multiple genes between two or more samples. This analysis can help scientists identify the molecular basis of phenotypic differences and select gene expression targets for in-depth study. Gene expression profiling provides valuable insight into the role of differential gene expression in normal biological and disease processes.

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Application note

Introduction to Gene Expression: Getting Started Guide

This guide is a good primer for new users looking to learn more about gene expression principles and practices. 


Expected Gene Expression Levels in Tissues for Use as Controls

Learn how to search public databases for expected gene expression levels in certain tissues.

How TaqMan Assays Work

A brief explanation and illustration of how the TaqMan chemistry works in the various applications of gene expression, genotyping, copy number variation, microRNA, mutation detection, and protein quantification.

Using TaqMan Endogenous Control Assays to Select an Endogenous Control for Experimental Studies

In any gene expression study, selection of a valid normalization or endogenous control to correct for differences in RNA sampling is critical to avoid misinterpretation of results. The expression level of a good control should not vary across the samples being analyzed.

Real-Time PCR: Understanding Ct

Learn more about Ct (threshold cycle), the intersection between an amplification curve and a threshold line. It is a relative measure of the concentration of target in the PCR reaction.

TaqMan Gene Expression Assays protocol

This TaqMan Gene Expression Assays protocol provides instructions for performing real-time reverse transcription-PCR (real-time RT-PCR) using TaqMan Gene Expression Assays and TaqMan non-coding RNA assays.


Genetic Analysis for All webinars

Learn how genetic analysis techniques, including sequencing, NGS, and quantitative and digital PCR, are being used by researchers to advance knowledge and innovations in challenging disease and research questions.


Ask TaqMan videos

Get answers to popular qPCR questions with our library of quick and easy how-to videos covering a variety of topics including experiment setup, best practices, and guidance on products and technologies.

Real-Time PCR Resource Library

Innovative tools and educational resources that help advance the work of researchers engaged in real-time PCR.

Additional resources