Final answer:
The ribosomes attach at the 5' end of mRNA and move towards the 3' end during translation, with translocation being facilitated by G proteins and EF-G.
Step-by-step explanation:
The ribosomes attach near the 5' end of the mRNA and then move towards the 3' end. This attachment occurs when the 30S ribosomal subunit recognizes the mRNA and anchors at the correct location, which is usually near the start codon AUG.
Following this, the 50S ribosomal subunit binds to the initiation complex to form a complete ribosome. During the process of translation, the ribosome moves along the mRNA strand towards the 3' end, a process facilitated by G proteins and GTP.
This is known as translocation, which involves the elongation factor-G (EF-G) also called translocase. As translocation of the ribosome occurs, a tRNA molecule recognizes a codon on the mRNA, binds to it via complementary base pairing, and adds the correct amino acid to the growing polypeptide chain.