Where do Viruses come from?

[werty8472]

There’s the creation theory and the evolution theory and all sorts of theories for how life started. However, the little crystal parasite- the virus- is not a living being by definition. Is there any knowledge as to where viruses came from? Or are there just as many theories as there are for living organisms?

[dolphinboy]

I think there are a few different theories out there. The one I remember from college was that they were some form of mutant mitachondial dna gone awry.

I don’t think that’s what they believe these days… but there not a lot of fossil viruses around to look at.

[dolphinboy]

make that Mitochondrial…

[Colibri]

It is no longer believed that viruses are a “primitive” form of life, that somehow preceded cellular life. Instead viruses are parasites, derived from the genetic material of cellular life. That is, viruses are descended (in a way) from cellular life, not the other way around.

[dolphinboy]

Here’s a link you can check out:

http://www.mcb.uct.ac.za/tutorial/virorig.html

[Colibri]

What should be stressed is that viruses have many different origins. The different groups of viruses are often more closely related to their host organism than they are to one another.

From dolphinboy’s link:

It is very quickly apparent from sequence studies that there can have been no single origin of viruses as organisms. . . . Thus, there can be no simple “family tree” for viruses; rather, their evolutionary descent must resemble a number of scattered “bushes”. Viruses as a class of organism must be therefore be considered to be polyphyletic in origins: that is, having a number of independent origins, almost certainly at different times, usually from cellular organisms.

[Cagey_Drifter]

regardless of where they come from-- which is a very interesting question-- I gotta say that they are some really creepy looking things. I cringe at the idea of billions of those things running around in me. ::shudder::

http://en.wikipedia.org/wiki/Image:Tevenphage.png

[Stranger_On_A_Train]

@Colibri

What should be stressed is that viruses have many different origins. The different groups of viruses are often more closely related to their host organism than they are to one another.

Viruses can also recombine, both with each other (via the mechanisms in living cells) and with the DNA of bacteria and even “higher” multicellular life. So, not only do they not have unique origins, but their evolutionary pathways may cross again and again, more like a spiderweb than a and evolutionary tree.

Viruses are “simple” in that they have a small set of protein coding instructions (in RNA), but are highly efficient as virtually all of the codons belong to active genes, as opposed to more complex animals, much of whose code is repeative or apparently vestigal (though not, as many evolutionary biologists note, useless…it’s just not in use currently). Viruses leave all of the heavy lifting to the machinery in the cells they invade and are content merely to direct cellular processes according to their own needs; so they’re more like battleaxe hired-gun CEOs clearcutting and cost-reducing (think ‘‘Chainsaw’’ Al Dunlap) than retarded children.

Stranger

[Triskadecamus]

DNA is not an essential part of a virus. Some have no DNA at all. I am not sure if it is common at all to viral structure. The existence of viral code sequences within the genomes of more highly complex life forms, including humans make it seem likely that among the many possible sources of viruses, creation within living beings by coding errors would be a fairly strong candidate.

Tris

[Colibri]

@Triskadecamus

DNA is not an essential part of a virus. Some have no DNA at all. I am not sure if it is common at all to viral structure.

They all have either DNA or RNA. The retroviruses, including HIV, use RNA as their genetic material.

The existence of viral code sequences within the genomes of more highly complex life forms, including humans make it seem likely that among the many possible sources of viruses, creation within living beings by coding errors would be a fairly strong candidate.

This can also be due to the fact that some viruses such as retroviruses incorporate themselves into the nuclear genome of the host.

From here

Eukaryotes are also known to acquire viral genes, and the phenomenon is not rare. “Endogenous retroviruses and retroviral elements have been found in all vertebrates investigated… As a general rule, the number of groups of viral sequences found within a given vertebrate species is proportional to the effort spent searching that species”

. . .
One example of a benefit conferred by viral genes comes from humans. A sequence installed by a retrovirus regulates the amylase gene cluster, allowing us to produce amylase in our saliva. This sequence that we share with a few other primates enables us to eat starchy foods we otherwise couldn’t (17).

In August, 1997, another whole-genome sequencing, of Helicobacter pylori, found that many genes in it are more similar to those of eukaryotes or archaea than other bacteria (18). “Such observations… are often interpreted as evidence of lateral gene transfer in the evolutionary history of an organism,” say the sequencers.

Additional evidence that genes can move across species boundaries even in eukaryotes comes in the June 13, 1997, issue of Science. A report there by Frederico J. Gueiros-Filho and Stephen M. Beverley of Harvard describes the “Trans-kingdom Transposition” of a gene-size piece of DNA known as a transposable element (19). The particular transposable element they studied, called mariner, has already been found in planaria, nematodes, centipedes, many insects, and humans

[Jon_the_Geek]

@Cagey Drifter

regardless of where they come from-- which is a very interesting question-- I gotta say that they are some really creepy looking things. I cringe at the idea of billions of those things running around in me. ::shudder::

http://en.wikipedia.org/wiki/Image:Tevenphage.png

If it makes you feel better, that’s a bacteria-infecting virus. Ebola doesn’t look nearly as much as some sort of alien invader, nor does HIV nor influenza. Mammalian viruses tend to be scarier than they look, to me at least.

[rowrrbazzle]

@Jon the Geek

If it makes you feel better, that’s a bacteria-infecting virus. .

With that in mind, I always found it fascinating that an organism’s head was in the shape of one of the 5 Platonic solids.