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).
When the mRNA code is read by the proteins that build the amino acid chain, it's not read as a sequence of individual letters. It's read in chunks of 3 letters, or 3 nitrogenous bases, at a time. Each set of 3 bases is a special code that indicates a different amino acid.The 3-base sets are called codons. codon is a series of 3 bases in mRNA that specifies a particular amino acid. Codons can also indicate a stop, or termination signal, but we'll get to that in a minute. For now, just think of codons as the basic unit for the genetic code.