No, amino acids are not only represented by one codon. Codons are made up of three nucleotides and each codon usually corresponds to a particular amino acid. There are 20 different amino acids that make up proteins and some of them are represented by more than one codon. For example, the amino acid leucine is represented by six different codons, serine by six, arginine by six, glycine by four, proline by four, alanine by four, threonine by four, valine by four, isoleucine by three, and asparagine by two. However, there is only one codon, AUG, that corresponds to the amino acid methionine and another, UGG, that corresponds to tryptophan.