A codon is a sequence of three nucleotides in DNA or RNA that corresponds to a specific amino acid or a stop signal during the process of protein synthesis. Each codon is part of the genetic code, which dictates how the information in genes is translated into proteins, the building blocks of life. In the genetic code, there are 64 possible codons, but only 20 different amino acids. This means that some amino acids are encoded by more than one codon. The correct sequence of codons is essential for producing proteins that function properly in living organisms.