Re: Viruses

From: Robert Bradbury (
Date: Tue Jan 25 2000 - 20:35:47 MST

On Tue, 25 Jan 2000, david gobel wrote:

> As an example of possible benefits, I have heard it postulated that viruses
> may provide a mechanism for the injection of novel DNA into otherwise stable
> mammalian genomes, and that action if true, may contribute to longer term
> species viability, but I have never heard whether this was confirmed or
> experimentally proved untrue.

Most of the junk DNA in the organisms of higher organisms is littered
with sequences derived from retrotransposons. These are mobile genetic
elements, highly related to viruses that suffle your DNA. The standard
textbook, "The Cell", describes viruses as "mobile genetic elements".

It would probably be an error to consider mammalian genome's "stable".
One of the reasons for the rise of mammals may have been the development
of more rapidly varying genomes, perhaps through retrotransposons
(I've never seen retrotransposons discussed in reptiles -- yeast,
Drosophila and mammals are typically cited.)

> Now for the REASON for the question...most research on viruses focus on the
> ideopatic/pathologically negative to humans action of viruses. What if there
> are massively useful but extraordinarily subtle benefits that viruses convey
> to humans about which we are totally ignorant. Is there any research on
> this? If no one is looking here, my intuition is that it would yield
> incredible fruit.
Shuffling the genome has both benefits and harms. Shuffling your MHC
genes makes you better able to resist the really harmful viruses
(by making more variant immune systems). Shuffling other parts of
the genome causes birth defects, cancer (esp. leukemia), etc.

I think the subtle benefits are likely to go hand-in-hand with
the less than subtle harms. Probably because its easier to
break something that works than it is to improve on something
that is already "improbably" functional, the harms exceed the


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