| 3' UTR | 5' UTR | CDS | exon | intron | primary transcript | mRNA |
| 3' UTR | 5' UTR | CDS | exon | intron | primary transcript | mRNA |
3' UTR. The 3' untranslated region (3' UTR) is a portion of a transcript present both in the primary transcript and the mature mRNA. It represents the portion of a gene between the stop codon and the last base of the transcript.
The 3' UTR is highlighted in red in the primary transcript and the mRNA; the corresponding region of the genome is also highlighted in red. The poly A tail is added to the 3' end of the 3' UTR.
Some genes contain introns within the 3' UTR. For such genes, the last exon will be noncoding.