MRNA is synthesized in transcription. During transcription, the DNA molecule unzips, and only one side serves as the template for the synthesis of the mRNA strand. Once synthesized, the mRNA molecule exits the nucleus and proceeds to the ribosomes for translation, or the making of a protein.
The synthesis of a strand of mRNA inside the nucleus of a cell is the first step to making a protein. An enzyme called RNA polymerase begins the process of transcription. The DNA unwinds and unzips, exposing a strand to serve as the template for making an mRNA strand. RNA polymerase adds bases to the growing mRNA strand one base at a time. The bases that make up RNA are adenine, guanine, cytosine and uracil. Following transcription, the RNA molecule is allowed to pass through the nuclear membrane into the cytoplasm where protein synthesis occurs. DNA is not allowed to exit the nucleus.