Main Page | See live article | Alphabetical index In genetics, the 3' UTR (read as 3 prime untranslated region) is a particular section of messenger RNA (mRNA). Like all strands of nucleic acid, mRNA is directional. One end is the 5' (five prime) end: the other is the 3' (three prime) end. When an enzyme uses messenger RNA's sequence to build a protein (the process is called translation), it starts reading from the 5' end, until it encounters a "start" codon. Amino acids are then added to the protein until the enzyme encounters a "stop" codon (three nucleic acids which tell the enzyme to stop). Anything beyond this stop codon is part of the 3 prime untranslated region (3' UTR). In a diagram: start stop codon codon ---------|-------------------|--------- 5'-UTR translated RNA 3'-UTR Many functional elements occur in the 3' UTR: Polyadenylation signals target the mRNA to the ribosome, where it is translated. SECIS elements, which can occur in the 3' UTRs of eukaryotic mRNAs, direct the ribosome to translate UGA codons as selenocysteines. The histone downstream element is analogous to polyadenylation in function, but has different sequence characteristics, and is used only for histone genes. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.