![]() A common example is found in eukaryotic genes - these genes often have introns, some of which are only spliced in some circumstances, so the in frame stop may be in different places for different transcripts from the same gene. †Note: As is often true in biology there are numerous caveats and exceptions. (January 2018) In genetics, attenuation is a regulatory mechanism for some bacterial operons that results in premature termination of transcription. §Note: The mechanisms are very different in prokaryotic and eukaryotic organisms - they can also vary between different species and even for different genes! The 3' UTR is simpler to identify - it is typically† everything after the first in frame stop codon and before the polyadenylation signal (where the polyA tail gets added. I also encourage you to look at some of the references for that section, which will help give you more detail on this high complex process that is still being actively studied. Compare: amber codon, ochre codon, umber codon. This is covered in a bit more detail in another article: ter·mi·na·tion co·don trinucleotide sequence (UAA, UGA, or UAG) that specifies the end of translation or transcription. The terminators of the present invention are especially optimized for the T7 RNA. (In fact, codons other than AUG are sometimes used as start codons!) Terminators are sequences that hinder or stop transcription of a polymerase. These sequences are bound by proteins that help guide the ribosome to assemble at the correct place to start translation. The short answer to that is that the sequence of the mRNA around a potential start codon influences whether or not it will be used§. Our results suggest that terminator choice can have a major effect on the performance and stability of a transgene and this therefore warrants more careful consideration. The interesting question is how does the ribosome know which start codon to start with? Frequently, little attention is paid to terminator sequences and their selection is based more on availability than performance. ![]() Translation has pretty much the same three parts, but they have fancier names: initiation, elongation, and termination. The 5' UTR is everything 5' of the start codon. A book or movie has three basic parts: a beginning, middle, and end. ![]()
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