Viral genetics, the study of the genetic mechanisms that operate during the life cycle of viruses, utilizes biophysical, biological, and genetic analyses to study the viral genome and its variation. The virus genome consists of only one type of nucleic acid, which could be a single- or double-stranded DNA or RNA. Single-stranded RNA viruses could contain positive-sense (+RNA), which serves directly as mRNA or negative-sense RNA (-RNA) that must use an RNA polymerase to synthesize a complementary positive strand to serve as mRNA. Viruses are obligate parasites that are completely dependant on the host cell for the replication and transcription of their genomes as well as the translation of the mRNA transcripts into proteins. Viral proteins usually have a structural function, making up a shell around the genome, but may contain some enzymes that are necessary for the virus replication and life cycle in the host...