pysäytyssekvenssin

Pysäytyssekvenssin, meaning stop codon in English, is a nucleotide triplet within messenger RNA (mRNA) that signals the termination of protein synthesis during translation. Instead of coding for an amino acid, these sequences act as a signal to the ribosome to release the newly formed polypeptide chain. There are three canonical stop codons in the standard genetic code: UAA, UAG, and UGA. These sequences are recognized by specific protein factors called release factors, which bind to the ribosome when a stop codon is encountered. This binding event triggers a conformational change in the ribosome, leading to the hydrolysis of the bond between the polypeptide chain and the last transfer RNA (tRNA), thus completing the translation process. The presence and position of stop codons are crucial for producing functional proteins; premature stop codons, often caused by mutations, can lead to truncated and non-functional proteins, a phenomenon known as a nonsense mutation. Conversely, the absence or alteration of stop codons can result in proteins that are longer than intended, potentially affecting their function and stability.