Biology · Molecular Biology and Translation Mechanics

In an in vitro translation reaction, the 43S pre-initiation complex (PIC) was incubated with the in vitro transcribed and capped mRNA for Gene X, followed by addition of the 60S subunit. As a control, mRNA for Gene Y isolated from cells was incubated in the same reaction. The mRNA for Gene Y was bound to the 80S ribosomes and polyribosomes, while mRNA of Gene X remained unbound. In a parallel experiment, mRNAs for both Gene X and Gene Y were found to be associated in vivo with 80S and polyribosomes. The following statements were made to explain the above observation: A. The in vitro system was globally defective for 80S assembly. B. Gene X mRNA has a sequence or structural feature that specifically prevents 80S assembly in vitro. C. Gene X mRNA lacks a start codon. D. Gene X mRNA requires other cellular factors which are absent in the in vitro mix to permit initiation. E. The in vitro assay preferentially degrades Gene X mRNA. Which one of the following options represents all correct statements?