Viruses are small infectious agents that can basically infect living cells and take over the processes that take place within that cell. Now, there are many different types of viruses that exist in nature and one way by which we can classify our viruses is based on the nucleic acid that is found within our virus. Now there are two major categories, categories of viruses. 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.