Definition of Gene expression

Gene expression: The translation of information encoded in a gene into protein or RNA. Expressed genes include genes that are transcribed into messenger RNA (mRNA) and then translated into protein, as well as genes that are transcribed into types of RNA such as transfer RNA (tRNA) and ribosomal RNA (rRNA) that are not translated into protein. Gene expression is a highly specific process in which a gene is switched on at a certain time and "speaks out."