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In genetics, a transcription terminator is a section of nucleic acid sequence that marks the end of a gene or operon in genomic DNA during transcription.This sequence mediates transcriptional termination by providing signals in the newly synthesized transcript RNA that trigger processes which release the transcript RNA from the transcriptional complex.
In the case of human malate dehydrogenase, the stop codon is read through with a frequency of about 4%. [31] The amino acid inserted at the stop codon depends on the identity of the stop codon itself: Gln, Tyr, and Lys have been found for the UAA and UAG codons, while Cys, Trp, and Arg for the UGA codon have been identified by mass spectrometry ...
Traditionally, the termination signal for translation is a 3 nucleobase sequence called a stop codon. [2] Research has shown that the nucleobases surrounding the stop codon can impact termination efficiency. [2] Specifically, the 4th base (nucleobase directly following the stop codon) has a significant impact on the termination efficiency. [2]
Conversely, while the uracil-rich sequence that follows the hairpin is not always necessary for termination, [6] it is hypothesized that the uracil-rich sequence aids in intrinsic termination because the U-A bond is not as strong as G-C bonds. [4] This inherent instability acts to kinetically favor the dissociation of the RNA transcript. [4]
That start codon (not necessarily the first) indicates where translation may start. The transcription termination site is located after the ORF, beyond the translation stop codon. If transcription were to cease before the stop codon, an incomplete protein would be made during translation. [3]
Finally, the transcription terminator sequence is transcribed. Whether transcription is coupled to translation determines whether this stops transcription. The terminator requires folding of the mRNA, and by unwinding mRNA structures the ribosome elects the formation of either of two alternative structures: the terminator, or a competing fold ...
The 5' UTR is upstream from the coding sequence. Within the 5' UTR is a sequence that is recognized by the ribosome which allows the ribosome to bind and initiate translation. The mechanism of translation initiation differs in prokaryotes and eukaryotes. The 3' UTR is found immediately following the translation stop codon.
Another specific addition signaled by the 3′-UTR is the incorporation of selenocysteine at UGA codons of mRNAs encoding selenoproteins. Normally the UGA codon encodes for a stop of translation, but in this case a conserved stem-loop structure called the selenocysteine insertion sequence (SECIS) causes for the insertion of selenocysteine ...