Definition for 3' untranslated region
From Biology Forums Dictionary
A region of the DNA which IS transcribed into mRNA and becomes the 3' end or the message, but which does not contain protein coding sequence. Everything between the stop codon and the polyA tail is considered to be 3' untranslated. The 3' untranslated region may affect the translation efficiency of the mRNA or the stability of the mRNA. It also has sequences which are required for the addition of the poly(A) tail to the message (including one known as the "hexanucleotide", AAUAAA).