Question

17. explain the strategy used by a plus-sense RNA virus, minus-sense RNA virus, DNA virus and retrovirus to get each of their genomes copied during replication [Hint: see the table if you cannot remember]

18. explain the strategy used by each of the following viruses to get host cells to make their proteins for them: double-stranded DNA, plus-sense RNA, minus-sense RNA, retroviruses [Hint: see the table if you cannot remember]

Answer 1

	Q. 17	Q. 18
DNA virus	enter host cell nucleus, get replicated with host cell DNA	DNA is transcribed and translated normally by host cell machinery to produce viral proteins
+ sense RNA virus	use viral RNA-dependent RNA polymerase (RdRp) to make double-stranded RNA intermediate, remain in cytoplasm, RdRp can make more copies of RNA	the viral RNA itself acts directly as mRNA for protein synthesis
- sense RNA virus	use viral RdRp to synthesize + sense RNA, the + sense RNA acts as template for synthesis of more copies of - sense RNA	+ sense RNA acts as mRNA for synthesis of viral proteins
Retrovirus	use viral reverse transcriptase (RT) to synthesize DNA, DNA is replicated by host cell machinery	DNA, formed by reverse transcription, is transcribed and translated normally by host cell machinery to produce viral proteins