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).
Synonymous Mutations (Silent Mutations). With 61 codons for 20 amino acids, many of the codons are synonyms, coding for the same amino acid. Each amino acid can be indicated by up to six different codons (in the case of leucine); only two (methionine and tryptophan) have only one codon.