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poly A tail (medicine)


poly A tail
<molecular biology> A sequence of adenine nucleotides that get added to the 3' end of some primary transcript messenger RNA molecules in eukaryotes during post-transcriptional processing. The added tail is believed to confer stability to the molecule.

Histone mRNA do not have poly A tail. The poly A tail is added post transcriptionally to the primary transcript as part of the nuclear processing of RNA yielding hnRNAs with 60-200 adenylate residues in the tail. In the cytoplasm the poly A tail on mRNAs is gradually reduced in length.

The function of the poly A tail is not clear but it is the basis of a useful technique for the isolation of eukaryotic mRNAs. The technique uses an affinity column with oligo(u) or oligo(dT) immobilised on a solid support. If cytoplasmic RNA is applied to such a column, poly A rich RNA (mRNA) will be retained.