Prions are formed by glycoproteins, don't have any n.a. (nucleic acid). I don't believe they're alive, as I'll explain later. I would also include in my theory of living things the proviruses wich (in accord with Temin) can evolve to retroviruses. It is, really, a difficult question, and that's the real point; because (and that's the original question of the thread) how can we say something is or isn't alive? Sure I mean something "organic" that fits some basic needs; and I think that the main think a "living" structure must do its self-reproduce, assure the continuity of the "specie", or, let's say, structure. Viruses are higly-arranged structures capable of replicating theirselves, that's why I think they're alive. Anyway, scientists all around the world don't reach an agreement on this point, so we don't have to agree about this. Just one thing; sorry about my english level!! Please Register or Log in to view the hidden image!