The transcription phase of protein synthesis occurs in the nucleus. During this phase, an enzyme produces a copy of the cell's DNA, creating ribonucleic acid. The RNA becomes messenger RNA, or mRNA, before exiting the nucleus and entering the cytoplasm.
Protein synthesis is the scientific term for protein production within a cell. Two phases, transcription and translation, must occur for the cell to produce proteins. During transcription, the enzyme RNA polymerase binds to a portion of the DNA called a promoter. The promoter helps the enzyme determine which part of the DNA to copy and in which direction to copy it, creating an mRNA transcript. At the end of the transcription phase, the cell must process the mRNA transcript to produce a mature mRNA transcript. Processing also occurs in the nucleus of the cell.
Translation occurs in the cytoplasm. During this phase, a ribosome attaches itself to the mRNA transcription, and then a transfer RNA molecule carries an amino acid to the ribosome. Amino acids are the basic units of a protein molecule. For the amino acid to bond with the transfer RNA molecule, it must have a matching code. A second transfer RNA molecule bonds to the ribosome, creating a bond between the two amino acids. Amino acids bond together to create the polypeptide chain that eventually becomes a protein.