We have DNA viruses which contain single or double stranded DNA and we also have RNA viruses that contain single or double stranded RNA molecules. Now let's begin by discussing DNA viruses. Now although single stranded DNA viruses do exist and one example is the Inovirus that infects bacterial cells, the more common type of DNA virus is the one that contains the double stranded DNA. Now basically what the DNA virus does is it infects that cell by essentially injecting our nucleic acid the single or double stranded DNA molecule inside that cell. And that DNA basically ends up in the nucleus of our cell. Now once in the nucleus of that cell, it can basically use the infected host cells machinery.