dactylospasm; Dactylosporangium aurantiacum subsp. hamdenesis; dactylozooid; dactylus-dactyly; Dad; daddy-long-legs; DADH; DADMS; DAF; DAF16; daffodil; Daffyâs Elixer; Dafilon; DAFNE; daft lamb; DAG; dagga; Dagger Sign; dagging; Dagnini; Dagnini, Giuseppe; Dagnini, Guido; dags; DAGU; DAH
These are comprised of 20 unique amino acids, and each is coded for by a stretch of DNA known as a codon. Codons are always 3 base-pairs (nucleotides) in length. DNA is made of 4 unique nucleotides; (A)denine, (G)uanine, (C)ytosine and (T)hymine. This means that there are 64 unique codons that can be made with these 4 bases (4*4*4). If codons were only 2 bases in length then the variety of codons that could be created would be less (only 16 unique sequences if there are still 4 nucleotides). More unique nucleotides would be required to get enough unique sequences to code for the 20 amino acids (as well as the STOP codons).
There are four bases in RNA (A,G,C and U), so there are 64 possible triplet codes (4 3 = 64). In theory only 22 codes are required: one for each of the 20 naturally occurring amino acids, with the addition of a start codon and a stop codon (to indicate the beginning and end of a protein sequence).