Viruses vs plasmids

[Ulrich Melcher]

1) Before the viral nature of the molecules responsible for the killer 
phenomenon in fungi (brewer's yeast and smut fungus) was discovered, the 
ds RNA molecules were, I think, called killer plasmids.  So, there is 
precedence for using the term "plasmid" with RNA.
2) Please also note that these were pathogenic RNAs.  So, I disagree 
with Ed who believes, I think, that a distinction between plasmids and 
viruses can be made on the basis of pathogenicity.
3) Most plasmids we use or look at have genes because we use the genes 
for selection or are interested in the properties carried by them.  If I 
were to take all the protein-coding genes out of a plasmid and put it 
back in a cell, it would probably still replicate extrachromosomally, 
though I might have a hard time finding it.  Is it a plasmid?  I think 
so.

Ulrich Melcher                 umelcher at bmb-fs1.biochem.okstate.edu
Department of Biochemistry     
  and Molecular Biology        Tel: 405-744-6210
246 NRC                        FAX: 405-744-7799
Oklahoma State University
Stillwater OK 74078-3035 USA