Use the following information to answer the question.
Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its 5′ end, the RNA genome has a viral protein (VPg) instead of a 5′ cap. This is followed by a non-translated leader sequence, and then a single long protein-coding region (~7,000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acids similar in structure to those that are found in viruses and other organisms. Short-period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides.
What conclusion is most consistent with the results of the radioactive labeling experiment?
A) Host cell ribosomes only translate the viral code into short polypeptides.
B) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
C) The RNA is translated into short polypeptides, which are subsequently assembled into large ones.
D) The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.

Question

Quizplus · Accepted Answer

The fact that short periods of labeling only result in labeling of very long proteins, while longer periods of labeling result in several different short polypeptides suggests that the RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones. This is consistent with the information given about the structure of the RNA genome, which has a single long protein-coding region followed by a poly-A tail.

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