The genetic code is called a universal code because all known organisms use the same four nucleotide bases; organism differ according to the arrangement of the nucleotide bases. The four nucleotide bases are adenosine, thymidine, cytidine and guanosine. Three bases form an amino acid, also known as a codon.
The codons form the basis of the genetic code. Amino acids are necessary to form the DNA, mRNA and tRNA that are required for the creation of new genetic material.
Scientists have learned that an extremely small amount of microbes use a different genetic code. Otherwise, fungi, plants, animals, bacteria and viruses all use the same codons for protein synthesis.