FIGURE 3-14 Transcription and Translation In protein synthesis (see Figure 3-13), a particular sequence of nucleotide bases in a strand of DNA (top) is transcribed into mRNA (center). Each sequence of three nucleotide bases in the mRNA strand (a codon) encodes one amino acid. In translation, the amino acids, directed by the codons, link together to form a polypeptide chain (bottom). The amino acids are tryptophan (Trp), phenylalanine (Phe), glycine (Gly), and serine (Ser).