Viruses are not "cells" (neither living nor non-living). They are merely a DNA or RNA enclosed in a protein shell. In this regard you are right, a virus contains either a DNA or an RNA, but not both.

Did you know an interesting fact? Viruses cannot penetrate plant cells walls, hence, they cannot directly infect plants. In order to infect plants, viruses transmit themselves through bacteria or other organisms that feed on such plants.

Read this article if you want to find out more about viruses: http://www.news-medical.net/health/V...robiology.aspx

More detailed information on viruses at this website: http://micro.magnet.fsu.edu/cells/virus.html