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Walter Ogston ogston at HOBBES.KZOO.EDU
Tue Oct 4 09:00:10 EST 1994

Ed Rybicki makes a comment about evolution of negative strand viruses,
to the effect that what has evolved must be advantageous because it has
evolved.  The problem with this proposition is that it is circular, and
doesn't explain anything interesting.  Nothing against Ed, lots of
people have done the same thing.  

The real challenge for the evolutionary biologist is to explain why a
particular structure or system favors the survival and replication (or
reproduction) of the organisms that posess it.  Comparison with
alternatives is important here.  And ideally the explanation should 
lead to an experiment or observation that will test the explanatory 

In the case of negative strand viruses, one significant difference from 
positive strand viruses is that the former can express several different 
mRNAs on infection, at different levels, whereas the latter can express 
only one mRNA, and in order to separate different genetic functions early 
in infection they have to go through the business of separating the
components of the polyprotein.  

Furtiher development of this argument is left as an exercise to the
Walter Ogston				ogston at hobbes.kzoo.edu
Department of Biology			Phone: (616)337-7010
Kalamazoo College			Fax:   (616)337-7251
Kalamazoo, MI 49006-3295

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