A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5'-AUGAAAAAAAAAAAAUAA-3' has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis?
(a) It inhibits peptidyl transferase activity.
(b) It inhibits movement of the small subunit relative to the large subunit.
(c) It inhibits release factor.
(d) It mimics release factor.
Answer: B