Gene expression

Every cell contains the entire genome (the full genetic blueprint), but only a certain set of genes is expressed at a given time. The set of genes that is expressed gives a cell its characteristics, its functionalities and when applicable, its specialization. This is a dynamic process, with genes expression being turned on and off in response to internal and external stimuli.

A gene is considered expressed when it is transcribed and a functional product produced. The direct product of transcription is an RNA molecule: messenger RNA (mRNA), regulatory RNAs (such as miRNAs) or structural RNAs (like rRNA). Regulatory and structural RNAs are already functional products while mRNAs have to be translated into a protein. In the case of protein-coding genes, the abundance of mRNA reflects the level of gene expression.

To measure gene expression levels, different techniques can be used, for example Next Generation Sequencing or quantitative PCR.