So this is in contrast to living organisms that contain DNA and always DNA as the carrier of the genetic information. So what exactly is a virus? Well, a virus is this non living agent that consists of a protein capsule and inside the protein capsule we have some type of genetic information. Now, that genetic information can either be in a form of DNA like in living cells or in RNA but will never find both DNA and RNA. It's either this DNA or this RNA. Never both.