The first stage of gene expression is the transcription step, ie the passage from ADn to mRNA, the RNA polymerase will read DNA (the TAC sequence) and will synthesize a complementary strand (AUG) in the form of mRNA (which will then undergo mRNA processing).
The second stage of gene expression is the translation of mRNA into protein: the AUG sequence of mRNA (supposed to be the start codon) is translated to the amino acid, methionine, via the ribosome and tRNA. The ribisome will read adjacent codons to form the polypeptide (several amino acids bonded together by peptide bonds).
