In DNA, the coding region is flanked by the promoter sequence on the 5 end of the template strand and the termination sequence on the 3 end. During transcription, the RNA Polymerase (RNAP) binds to the promoter sequence and moves along the template strand to the coding region. RNAP then adds RNA nucleotides complementary to the coding region in order to form the mRNA, substituting uracil in place of thymine. This continues until the RNAP reaches the termination sequence.
After transcription and maturation, the mature mRNA formed encompasses multiple parts important for its eventual translation into protein. The coding region in an mRNA is flanked by the 5 untranslated region (5-UTR) and 3 untranslated region (3-UTR), the 5' cap, and Poly-A tail. During translation, the ribosome facilitates the attachment of the tRNAs to the coding region, 3 nucleotides at a time (codons). The tRNAs transfer their associated amino acids to the growing polypeptide chain, eventually forming the protein defined in the initial DNA coding region.