Gene expression is the process by which the heritable
information in a gene, the sequence of DNA base pairs, is made
into a functional gene product, such as protein or RNA. The
basic idea is that DNA is transcribed into RNA, which is then
translated into proteins. Proteins make many of the structures
and all the enzymes in a cell or organism. Several steps in the
gene expression process may be modulated (tuned). This includes
both the transcription and translation stages, and the final
folded state of a protein. Gene regulation switches genes on and
off, and so controls cell differentiation, and morphogenesis.
Gene regulation may also serve as a basis for evolutionary
change: control of the timing, location, and amount of gene
expression can have a profound effect on the development of the
organism. These changes may remain through cell divisions for
the remainder of the individual's life and may also last for
multiple generations. However, there is no change in the
underlying DNA sequence of the organism. In