Final answer:
Influenza Virus mRNA receives a Poly(A) tail through host cellular machinery, where an enzyme cleaves the pre-mRNA at a specific sequence and poly-A polymerase adds adenine residues, providing protection and signaling export to the cytoplasm.
Step-by-step explanation:
The Influenza Virus mRNA receives a Poly(A) tail through a process similar to that seen in eukaryotic mRNA processing. However, the mechanism is slightly different due to the virus's use of the host's machinery. In eukaryotic cells, once the elongation of the pre-mRNA is complete, the newly synthesized strand is cleaved by an endonuclease between an AAUAAA consensus sequence and a GU-rich sequence.
This cleavage leaves the AAUAAA sequence on the pre-mRNA. Subsequently, an enzyme called poly-A polymerase recognizes this sequence and begins to add a string of approximately 200 adenine (A) residues, which is known as the poly-A tail. This modification not only protects the pre-mRNA from degradation but also plays a role in the export of the mRNA from the nucleus to the cytoplasm.