Now a special category of RNA viruses include something called a retrovirus. So these viral agents. These RNA viruses contain a protein enzyme known as reverse transcriptase. And what reverse transcriptase basically does is once the RNA is inside the cytoplasm of the cell the reverse transcriptase basically transcribes our RNA into DNA which is in the opposite direction of normal transcription. And then once that viral DNA is synthesized it can go into the nucleus of that cell and in the nucleus of the cell it can be incorporated or integrated with the cell's own DNA genome. Now when the cell replicates its DNA and divides it passes down the viral DNA portion to the offspring cells.