Poly-A tail

Definition

The poly-A tail is a stretch of adenine nucleotides added to the 3' end of an mRNA molecule during RNA processing. It plays a crucial role in the stability, export, and translation of the mRNA.

5 Must Know Facts For Your Next Test

1. The poly-A tail is added post-transcriptionally by the enzyme poly(A) polymerase.
2. It protects mRNA from degradation by exonucleases in the cytoplasm.
3. The length of the poly-A tail influences mRNA stability and translational efficiency.
4. Polyadenylation signals in the DNA sequence dictate where the poly-A tail is added.
5. Eukaryotic mRNAs generally have longer poly-A tails compared to prokaryotic RNAs, which often lack them.

Review Questions

• What enzyme is responsible for adding the poly-A tail to an mRNA molecule?
• How does the length of a poly-A tail affect mRNA stability?
• Why is the poly-A tail important for mRNA export from the nucleus?

Related terms

mRNA:

Messenger RNA, a type of RNA that carries genetic information from DNA to ribosomes for protein synthesis.

Polyadenylation Signal: A specific sequence in DNA that signals where polyadenylation and addition of the poly-A tail should occur.

Exonuclease: An enzyme that degrades RNA molecules by removing nucleotide sequences from their ends.