Stop codon
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In molecular biology, a stop codon is a codon that signals the termination of the translation process of the current protein. Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein; stop codons signal the termination of this process by binding release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain.
An example of a single base deletion forming a stop codon.
Genetic code
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The genetic code is the set of rules used by living cells to translate information encoded within genetic material into proteins. Translation is accomplished by the ribosome, which links proteinogenic amino acids in an order specified by messenger RNA (mRNA), using transfer RNA (tRNA) molecules to carry amino acids and to read the mRNA three nucleotides at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries.
Axes 1, 2, 3 are the first, second, and third positions in the codon. The 20 amino acids and stop codons (X) are shown in single letter code.
Grouping of codons by amino acid residue molar volume and hydropathicity. A more detailed version is available.