Complete question:
Question: 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 molecule is digested by restriction enzymes in the nucleus.
B) The MRNA could not exit the nucleus to be translated.
c) The molecule is digested by exonucleases since it is no longer protected at the 5' end.
D) The cell recognizes the absence of the tail and polyadenylates the mRNA.
E) The molecule attaches to a ribosome and is translated, but more slowly.
Answer:
c) The molecule is digested by exonucleases since it is no longer protected at the 5' end.
Explanation:
The primary transcript formed by transcription in eukaryotes is modified by the addition of a structure called 5' cap at its 5' end. It refers to 7-methylguanosine that is linked to the 5' end of the primary transcript. The presence of 7-methylguanosine at the 5' end protects the mature mRNA against digestion by ribonucleases. Therefore, insertion of mRNA without a 5' cap into a eukaryotic cell would result in the breakdown of the inserted mRNA.
