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).
Because there are 64 possible combinations of four bases in three-nucleotide sequences, but (usually) only 20 amino acids that are translated, in order for most codons to be sense codons, that is, encoding an amino acid, then some of those amino acids must be specified by more than one codon.ndeed, most amino acids are specified by more than one codon such that only three of the 64 total codons are nonsense codons, that is, which specify instead stop codons. Compare with lack of ambiguity in the genetic code. See also lack of punctuation between codons.