Stoppkoodoni

Stoppkoodoni, also known as a stop codon, is a nucleotide triplet within a messenger RNA (mRNA) molecule that signals the termination of translation. Translation is the process where the genetic code carried by mRNA is used to synthesize proteins. In the standard genetic code, there are three such codons: UAA, UAG, and UGA. These codons do not correspond to any amino acid and instead serve as signals for ribosomes, the cellular machinery responsible for protein synthesis, to release the newly formed polypeptide chain. When a ribosome encounters a stop codon on the mRNA, release factors bind to the ribosome, triggering the hydrolysis of the bond between the polypeptide and the transfer RNA (tRNA) carrying the last amino acid. This effectively ends the elongation phase of protein synthesis. The presence and correct positioning of stop codons are crucial for producing functional proteins of the appropriate length. Mutations that alter or create stop codons can lead to truncated or extended proteins, often resulting in non-functional or aberrant proteins, which can have significant biological consequences, including disease.