Final answer:
Retroviruses like HIV have RNA genomes that are not initially capped or polyadenylated upon entering the host cell; these structures are an aspect of eukaryotic mRNA processing.Correct option is (A).
Step-by-step explanation:
In eukaryotic cells, mRNAs are typically processed to have a 5' cap and a poly(A) tail. Instead, these structures are added by the host cell after the virus has entered. The 5' cap is added to the RNA molecule to protect it from degradation and to aid in translation.
The poly(A) tail is added to the 3' end of the RNA molecule and is involved in several processes, including mRNA stability and transport. However, when it comes to viruses, the way their RNA is structured can vary. For instance, retroviruses like HIV, which are a type of RNA virus, carry an RNA genome that is reverse-transcribed into DNA, which then integrates into the host cell's genome.
This RNA is not initially capped or polyadenylated, as these modifications are characteristic of host cellular processes. The influenza virus, however, has an RNA genome that is segmented and already contains a 5' cap stolen from host mRNA molecules, while the poly(A) tail is generated through transcriptional processes specific to the virus. Based on this information, the answer to the question is:
The viruses enter with a complete 5' cap and poly(A) tail, although the mechanisms by which these structures appear on the viral RNA can be different from those used by host cells to modify their own mRNA.