Gene expression is an important aspect to inheritance. This is the process in which the information of a gene is formed into a functional gene product such as protein or RNA. Gene regulation may also serve as a substrate for evolutionary change, since control of the timing, location, and amount of gene expression can have a profound effect on the functions (actions) of the gene in the organism. Gene regulation also effects the expression as well. Gene regulation refers to the cellular control of the amount and timing of changes to the appearance of the functional product of a gene.

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An expression system consists, minimally, of a source of DNA and the molecular machinery required to transcribe the DNA into mRNA and translate the mRNA into protein using the nutrients and fuel provided. Overexpression can occur also. In the laboratory, the protein encoded by a gene is sometimes expressed in increased quantity. This can come about by increasing the number of copies of the gene or increasing the binding strength of the promoter region.