Final answer:
Viral RNA often features unique structures at its ends, linear DNA viruses have specific end formations for DNA replication, and integrated viral DNA into the host genome is flanked by host DNA with no distinct end features.
Step-by-step explanation:
At the ends of viral RNA, such as that of retroviruses like HIV, you can find unique structures necessary for its life cycle. Retroviruses have single-stranded RNA that, once inside a host cell, is converted by reverse transcriptase into double-stranded DNA (dsDNA). This integrated DNA, called a provirus when incorporated into the host genome, typically has long terminal repeats (LTRs) at both ends, which play a critical role in the integration and expression of the viral genes.
In contrast, linear DNA viruses possess double-stranded DNA with ends that may be either blunt or cohesive (overhanging ends). These features are critical for the virus's ability to replicate its DNA within the host cell.
Once a retrovirus's DNA is integrated into the host genome, it is flanked by the host’s DNA sequence at the integration sites, with no specific sequence characteristics defining the very ends of integrated viral DNA.