- One way in which a virus gains control of a cell is to direct the synthesis of new viral proteins, which include such molecules as enzymes. To do this, however, the virus must provide the cell with mRNA for the production of such proteins. Viruses can achieve this goal in one of three basic ways: (1) they can import mRNA into the cell in the form of the viral genome (2) they can allow the cell to make viral mRNA through normal cellular genetic processes by providing the cell with viral DNA (3) they can use unique mechanisms to convert their genomes into a form suitable for protein production • ex. + ssRNA virus; this type of genome essentially mimics the mRNA found in the cell • ex. DNA virus, either ds or ss, which can take advantage of normal cellular processes to produce mRNA • ex. - dsRNA virus, which uses a novel enzyme called RNA - dependent RNA transcriptase to convert its genome into + ssRNA, which can then be used for protein synthesis