In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find?
A) The mRNA could not exit the nucleus to be translated.
B) The cell recognizes the absence of the tail and polyadenylates the mRNA.
C) The molecule is digested by restriction enzymes in the nucleus.
D) The molecule is digested by exonucleases since it is no longer protected at the 5' end.
E) The molecule attaches to a ribosome and is translated, but more slowly.

Question

Quizplus · Accepted Answer

The 5' cap and poly-A tail are essential for protecting the mRNA molecule from degradation by exonucleases. Without these protective structures, the mRNA is vulnerable to degradation and will likely be digested by exonucleases. Therefore, choice D is the correct answer. Option A is incorrect because the mRNA can still exit the nucleus even without the cap and tail, but it may be degraded before it can be translated. Option B is unlikely because the cell cannot recognize the missing structures to add them. Option C is unlikely because restriction enzymes do not digest mRNA. Option E is incorrect because translation may not occur since the mRNA could already have been degraded by exonucleases.

In an Experimental Situation, a Student Researcher Inserts an MRNA