Talmudic Question #74

by Welkin Johnson

Do the seven strategies in the Baltimore scheme of viral replication represent all possible ways of being a virus? Have other strategies fallen by the evolutionary wayside?

Comments

[Christoph Weigel]

falling outside the Baltimore scheme: viroids. 'outside' because they cannot be traced down to the mRNA-centered scheme - despite apparently relying on host RNA pol 2 for replication. but certainly not fallen by the evolutionary wayside.
Christoph

Ah, viroids.... Don't they enliven the conversation... Thanks for bringing them up.

Elio

[Vincent Racaniello]

The original scheme proposed by Baltimore in the 1970s had only six genomes - the gapped, dsDNA genome of hepadnaviruses had not yet been discovered. So if you had asked this question then, the answer would have been that there are no dsDNA genomes with reverse transcription in their life cycle. Today we can suggest that an eighth class, ssDNA genomes with a reverse transcription step, have not yet been discovered. There could also be a ninth class - ambisense RNA genomes (which indeed exist). There could also be ssRNA(-) sense viruses with a reverse transcriptase, and dsRNA viruses with a reverse transcriptase - for 11 genome classes.

Vincent,

Wow! It look like you know something about viruses!!
Elio