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Tools for genetics and genomics: Gene expression profiling

Avrum Spira, MD, MSc
Katrina Steiling, MD, MSc
Section Editor
Benjamin A Raby, MD, MPH
Deputy Editor
Jennifer S Tirnauer, MD


The genetic basis for disease is determined by the inheritance of genes containing specific sequences of deoxyribonucleic acid (DNA). The phenotypic expression of these genes, through the synthesis of specific proteins, involves interaction with environmental signals that trigger activation of particular genes.

According to the central dogma of biology, ribonucleic acid (RNA) is transcribed from a DNA template; messenger RNA (mRNA) is then translated into protein (figure 1). Transcription and translation underlie gene expression.

Approximately 3 to 5 percent of genes are active in a particular cell, even though all cells have the same information contained in their DNA. Most of the genome is selectively repressed, a property that is governed by the regulation of gene expression, mostly at the level of transcription (ie, the production of messenger RNA from the DNA). In response to a cellular perturbation, changes in gene expression take place that result in the expression of hundreds of gene products and the suppression of others. This molecular heterogeneity can affect when and how a disease presents clinically in an individual with genetic predisposition to a condition and how individuals with a given disease will respond to specific treatments.

Analyses of gene expression can be clinically useful for disease classification, diagnosis, prognosis, and tailoring treatment to underlying genetic determinants of pharmacologic response.

This topic will focus on the role of mRNA in the cell, platforms for profiling mRNA expression, the challenges in interpreting the data from these analyses, and the emerging clinical applications of gene expression measurements. An overview of molecular genetics in clinical oncology is presented separately. (See "Principles of molecular genetics".)

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Literature review current through: Nov 2017. | This topic last updated: Sep 01, 2017.
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