Final Answer:
1.RNA biosynthesis involves transcription, generating mRNA from DNA. In single-stranded RNA viruses, the process depends on the polarity (+/-) of the RNA strand.
2.Replication occurs in different cellular locations based on the virus type: cytoplasm for some RNA viruses and nucleus for others.
3.RNA polymerase is the primary enzyme responsible for transcribing the genome into RNA.
4.The enzyme involved in transcription can be both host-encoded (utilizing host RNA polymerases) and viral-encoded (some viruses encode their own RNA polymerases).
Step-by-step explanation:
1.RNA Biosynthesis and Polarity: RNA biosynthesis, or transcription, converts genetic information from DNA to RNA. In the context of single-stranded RNA viruses, the polarity of the RNA strand (+/-) affects the process. For instance, in positive-sense RNA viruses (+), the viral RNA can act as mRNA directly and can be translated into proteins upon entry into the host cell. In negative-sense RNA viruses (-), the RNA strand needs to be transcribed into a complementary mRNA strand before translation.
2.Location of Replication: The replication sites vary among viruses. Some RNA viruses replicate in the cytoplasm, such as picornaviruses (e.g., poliovirus), while others, like influenza viruses, replicate in the nucleus of the host cell.
3.Enzyme for Transcription: RNA polymerase is the primary enzyme responsible for transcribing the genetic information from DNA into RNA. In the case of RNA viruses, this RNA polymerase can be either host-encoded (using the cellular RNA polymerases) or viral-encoded (viruses encode their own RNA polymerases).
4.Host or Viral Encoded Enzyme: Depending on the virus, the enzyme involved in transcription can be both host-encoded (utilizing the host cell's machinery) or viral-encoded (some viruses carry their own RNA polymerases to transcribe their genetic material).