Re: Evolution and Bacteria


hersh...@xxxxxxxxxxx wrote:
> Stanley Friesen wrote:
> > sharon@xxxxxxxxxxxxxxxxxxxxx wrote:
> >
> > >Add Hepatitis C to the list, I knew of somebody who had contracted that
> > >virus, and he told me it could eventually lead to liver disease --these
> > >are permanent in the blood/body fluids is my understanding?
> >
> > If it is a retro-virus, yes, it usually is.
>
> Hepatitis C is a flavivirus and is a positive (coding) strand RNA virus
> that replicates by use of an RNA-directed RNA polymerase. It is not a
> retrovirus. There is no integrated DNA form that I know of. Chronic
> (as opposed to acute) infection is poorly understood, but probably
> involves low-level replication rather than integration. In this it is
> similar to herpes viruses (which are dsDNA viruses that can lay around
> in a cryptic state with occassional flares). Which is why there is the
> joke about the difference between herpes and true love (ans: herpes is
> forever).
>
> Hepatitis B virus, however, does have many similarities to retroviruses
> in its mode of replication, even though it spreads as a DNA virus.

It does not, however, insert into the host genome. It resides in the
nucleus as an extrachromosomal circular DNA molecule.

>
> Hepatitis A is an RNA virus (not a retrovirus) and only seems to cause
> acute disease.
>
> Virus replication and genomes are the most diverse in biosphere, with
> dsDNA, ssDNA, ss(+)RNA, ss(-)RNA, and dsRNA forms with replication that
> is RNA only, DNA only, and switch-hitters of various kinds. There are
> even replicative entities (viroids) that are highly ds-like RNAs (but
> topologically a ssRNA circle that anneals to itself) which encode no
> proteins whatsoever. That is in addition to satellite (parasitic)
> viruses that require other viruses to replicate.
>
> > What retro-viruses often do
> > is insert themselves into the host's own chromosomes. Once this has
> > happened there is pretty much no way to eliminate it without killing the
> > host.
>
> Not quite true. Sometimes there are viral surface antigens that can be
> attacked. But it is quite clear that the viruses that do engage in
> chronic infection do so because it, from their viewpoint, is
> selectively advantageous. Most HepC and/or HepB infections are spread
> from carriers rather than people who only have the accute infection.
>
> > >I suppose that would be a lot of work --mapping the genome and figuring
> > >out how to genetically modify it where the virus itself would destroy
> > >or neutralize the ill effects of the virus. Lots of money, or
> > >completely impossible?
> > >
> > I was actually thinking more along the lines of deliberately selecting
> > for less harmful forms. The problem with the genetic engineering is
> > that the engineered form might not compete well with the wild form, so
> > would do little good. One would need a very aggressive engineered mild
> > form that corrupted the wild form as well.
> >
> > --
> > The peace of God be with you.
> >
> > Stanley Friesen

.

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