Question

A scientist translates an enzyme from pre-processed cell mRNA in a test tube (in vitro). However, the in vitro enzyme is found to be inactive compared to the extracted in vivo enzyme from a live cell culture. Which statement is the LEAST likely explanation for this phenomenon?

A. The extracted mRNA contains introns, which were translated as well.
B. A nonsense mutation occurred in the extracted mRNA.
C. The in vitro enzyme was not phosphorylated.
D. The in vitro enzyme was not cleaved into its active form.
E. Molecular chaperones were not present in vitro to properly fold the enzyme.

Answer 1

The least likely explanation for the inactivity of an in vitro translated enzyme compared to the in vivo extracted enzyme is the presence of introns in the mRNA, as introns are typically removed during mRNA processing in the nucleus before the mRNA is used for protein translation. Option a.

Step-by-step explanation:

When considering why an enzyme produced in vitro from pre-processed cell mRNA is inactive compared to its in vivo counterpart, the least likely explanation is that (A) the extracted mRNA contains introns, which were translated as well. This is because introns are normally removed during mRNA processing before translation into protein occurs. In the eukaryotic cell, introns are spliced out of pre-mRNA to produce mature mRNA that does not contain introns before it leaves the nucleus. Therefore, the mRNA used for in vitro translation should be devoid of introns if it is properly processed. Other explanations such as lack of phosphorylation, proper cleavage, or the absence of molecular chaperones to assist in folding are more likely to be the reasons for the resultant inactive enzyme in vitro.