Final answer:
A hypothesis for the advantage of the poly-A tail is that it protects mRNA from degradation, assists in mRNA export from the nucleus, and helps regulate mRNA stability, all of which are crucial for efficient protein synthesis.
Step-by-step explanation:
A hypothesis to explain the advantage of the poly-A tail added to the 3' end of the mRNA might suggest that this modification is crucial for the stability and functionality of mRNA molecules. The poly-A tail is added to mRNA by the enzyme poly-A polymerase following transcription. Key roles of the poly-A tail include protection of the mRNA from enzymatic degradation, assistance in the export of mRNA from the nucleus into the cytoplasm, and regulation of mRNA stability during translation.
The polyadenylation signal, typically a sequence like AAUAAA, directs where the mRNA will be cleaved and where the poly-A tail will be added. This poly-A tail can be envisioned as a buffer zone that gets shortened each time the mRNA is translated by ribosomes, hence regulating the half-life of the mRNA transcript. Blocking the addition of the poly-A tail through inhibition of poly-A polymerase would result in mRNA molecules that are more susceptible to degradation and have impaired transport out of the nucleus, significantly reducing their efficacy in protein synthesis.