Final answer:
A set of three-letter combinations of nucleotides called codons represents the genetic code, which is essential in the synthesis of proteins.
Step-by-step explanation:
A set of three-letter combinations of nucleotides called codons, each of which corresponds to a specific amino acid, represents the genetic code. In the process of protein synthesis, the genetic code is read from an mRNA molecule. Each codon consists of a sequence of three nucleotides read in a 5' to 3' direction, and this trinucleotide sequence is what dictates the sequence of amino acids in a protein. With 64 possible combinations resulting from the three-nucleotide code, multiple codons can correspond to the same amino acid.