Final answer:
The 5'-end 7methyl-GTP cap and the 3'-end poly(A) tail are post-transcriptional modifications of mRNA, which protect it from degradation and aid in protein synthesis initiation.
Step-by-step explanation:
The 5'-end 7methyl-GTP cap and the 3'-end poly(A) tail are two post-transcriptional modifications of mRNA (messenger RNA). The 5' cap is added to the pre-mRNA while it's still being synthesized, and it helps protect the mRNA from degradation, as well as being recognized by factors involved in protein synthesis to initiate translation. The 3' poly-A tail, added by an enzyme called poly-A polymerase, further protects the mRNA from degradation, assists in mRNA export from the nucleus, and is significant for subsequent binding to proteins for cytoplasmic transport and translation initiation.