[...lets split up... (OP)]

I'm not quite sure if this question is in the right category.

I was reading my Popular Mechanics magazine the other day and there was an article concerning the search for life of a different origin to what we see around us (fauna, flora and everything else), the article was about searching for that life on earth. The reasoning is that if life happened once, why couldn't it happen again. They would refer to it as a shadow biosphere, and suggested if it were to exist it would probably be in the form of microbes, or exist in extreme environments.

My question is could it be possible that viruses belong to a different biosphere? I've read a theory somewhere that a virus broke off from the DNA of cell and became it's own thing, but i'm not so sure. Could it be possible that DNA is a constant for life and that a virus came from a different source? And i'm not sure how to explain why a virus is reliant on cells for reproduction instead of being able to reproduce themselves.

Some answers from someone who knows more would be much appreciated.

[...lets split up... (OP)]

The crickets chirping in  the vast silence that is this post lead me to wonder "Was this a stupid question?"

[rosy]

Well, some viruses have an RNA genome, there's no actual requirement for DNA at any point in their cycle. But all cells use RNA, even though they use DNA as a storage medium. So I don't think there's any particular reason to attribute viruses to another biosphere as it would have to be one with basically the same transcription/translation behaviour as ours... and I'd think in order for us not to have spotted this "shadow biosphere" it would really have to be very "other" (maybe not even carbon based).
But I speculate wildly.

[Ophiolite]

Fred Hoyle was a proponent of panspermia, the origin of life elsewhere and its later arrival on the Earth. Beyond this he thought some viral epidemics were spaceborne diseases. His views were generally ignored (at best), or ridiculed by the science community in general. Wickramasinghe, one of his doctoral students and now Professor of Astronomy at Cardiff, continues to promote and research these ideas.

[Madidus_Scientia]

if life happened once, why couldn't it happen again

Well life as we know it today could not have began in an atmosphere containing so much oxygen, as oxygen atoms tend to rip other molecules apart. Life slowly evolved to be able to utilize oxygen. So if new life was come into existence today it would probably indeed be in an extreme environment.