Menu

[pretotr at urz.unibas.ch]

In article <39blpf$efr at news.CCIT.Arizona.EDU>, Martinez Hewlett <hewlett at brahms.biosci.arizona.edu> writes:
>>
>>The place in the world today where there is the most evolutionary
>>pressure on viruses is the laboratory.  Unintentional or intentional.
> 
> I really don't think that's true.  Most viruses growing in laboratory are
> subjected to such a narrow range of conditions that only a very limited
> genotype can survive.  A case in point is poliovirus.  At one point the
> CDC looked at (by RNA fingerprinting) samples of poliovirus that had been
> propagated for many years in widely separated laboratories.  In all
> cases, using this limited technology, the viral RNA was the same.  In
> contrast, one passage of vaccine strain through a human can result in any
> number of genotypes, some of which may even be revertant.
> 
> We found the same thing when examining the laboratory passage of LaCrosse
> encephalitis virus and snowshoe hare virus.  Laboratory passage produced
> selected few variations in nucleic acid sequence, wherease viruses
> isolated in the wild at different times varied widely.  (Reference:  M.
> J. Hewlett, J. P. M. Clerx, C. M. Clerx-van Haaster, L. J. Chandler, D.
> M. McLean and B. J. Beaty (1992), Genomic and biologic analyses of
> snowshoe hare virus field and laboratory strains, Amer. J. Trop. Med.
> Hyg., 46, 524-532)
> 
> Martin Hewlett
> Department of Molecular and Cellular Biology
> Univeristy of Arizona
> Tucson, Arizona  85721

Hmm, doesn't little variation indicate a high selective pressure?!
I would expect to see great variation, only when there is not much 
selective pressure.

Any comments?

Rene