The genetic code

Genetic information is information for synthesizing proteins, and since proteins consist of 20 different amino acids bonded in particular sequences, the genetic information must tell how to position the amino acids correctly in a polypeptide chain.

It is believed that each of the 20 different amino acids is represented in a DNA molecule by a particular sequence of 3-nucleotide groups. That is, the sequence C, G, A in a DNA strand represents one kind of amino acid; the sequence G, C, A represents another kind, and T, T, A still another kind.

Genetic Code For Certain Amino Acids 

Thus, the sequence in which the nucleotide groups are arranged within a DNA molecule can denote the arrangement of amino acids within a protein molecule. This method of storing information used for the synthesis of particular protein molecules is termed the genetic code.

Although DNA molecules are located in the chromatin within a cell's nucleus, protein synthesis occurs in the cytoplasm. Therefore the genetic information must somehow be transferred from the nucleus into the cytoplasm. This transfer of information is the function of certain RNA molecules.