Final answer:
The 3′ end of mRNA is not directly involved in the initiation of translation in eukaryotes; it mainly contributes to mRNA stability and efficient translation through a loop structure involving the 5' cap.
Step-by-step explanation:
In eukaryotes, the 3′ end of the mRNA is not directly involved in the initiation of translation. The initiation of translation begins when the small ribosomal subunit, along with initiation factors and the initiator tRNA, binds to the 5' cap of the mRNA, not the 3' end. The initiation complex then scans along the mRNA in the 5' to 3' direction, searching for the AUG start codon, according to Kozak's rules. The 3' poly(A) tail, though, is important for the stability and lifetime of the mRNA. It, along with the 5' cap, protects the mRNA from degradation and aids in its export from the nucleus. Moreover, the cap-binding protein and several other initiation factors form a loop with the mRNA by binding to its poly-A tail, enhancing the efficiency of translation initiation.