In the simplest sense, expressing a gene means manufacturing its corresponding protein, and this multilayered process has two major steps. In the first step, the information in DNA is transferred to a messenger RNA molecule by way of a process called transcription. During transcription, the DNA of a gene serves as a template for complementary base-pairing, and an enzyme called RNA polymerase 2 catalyzes the formation of a pre-RNA molecule, which is then processed to form a mature RNA. The resulting RNA is a single-stranded copy of the gene, which next must be translated into a protein molecule.
