Is a virus alive?

[Vkothii]

Is a virus like a special kind of package, that can "move sideways" energy-gradient wise, or has certain functionality (similar to a battery-powered tool), or is it a "minimised" lifeform?

Is it animate or inanimate information?
Does the distinction matter, does it cast any light on our view of the structure and function of DNA, and enzymes?

 

[Hercules Rockefeller]

Does the distinction matter….?

No.

…does it cast any light on our view of the structure and function of DNA, and enzymes?

No.


Whether a virus is alive or not is a semantic argument. The answer depends on the definition of life that you employ. Use different definitions and the answer changes. The traditional definition of life usually employs one or more of several different criteria. (See wikipedia). By these criteria a virus is not alive.

But these days its fashionable (especially on internet science forums) for people to employ other criteria that allow them to conclude that viruses are alive. Usually the argument revolves around the idea that viruses’ genomes change over time through natural selection (ie they evolve), so they must be considered alive. Or something like that. I don’t buy into it; the traditional measures have always been good enough for me.

At the end of the day it makes absolutely no difference to the study of viruses, whether it is pure science or clinical research. It certainly makes no difference to a virus whether or not we deem it to be living or not.

 

[Repo Man]

I've always found the question interesting because either way, we're dealing with something that is right on the edge of our understanding of life. Going from non living chemical reactions to living ones. I think that studying such things demystifies the idea of what living things are, and helps to take life down from the pedestal most humans have placed it on. Even more so with prions.

 

[Roman]

It's a semantic one, due to the propensity to view life as some sort of element, force, or secret sauce. Life is chemical reactions. Complicated ones, but reactions just the same. Virtually every scientific investigation into life has reaffirmed this. The stomach was considered to be full of magic juices that transformed food stuff into nourishment. Then they figured out it was just HCl.

 

[Vkothii]

…does it cast any light on our view of the structure and function of DNA, and enzymes?

No.

That's a very informative answer.
Why does a virus have to invade a cell to get its DNA replicated? How does it invade a cell? Why does a virus "carry" its DNA around? Why isn't viral DNA just "floating around" like dust particles? Why are viruses organised the way they are?

Is the answer "No"?

 

[invert_nexus]

That's a very informative answer.

Combined with the rest of his post, it was.

Why does a virus have to invade a cell to get its DNA replicated?

1. Viruses don't always have DNA.

2. Because that's how viruses work.

How does it invade a cell?

Various mechanisms. Do you have a particular virus in mind?

Why does a virus "carry" its DNA around?

1. Viruses don't always have DNA.

2. If it didn't, who would? (By the way, it doesn't necessarily have to. Ever heard of shingles?)

Why isn't viral DNA just "floating around" like dust particles?

Floating viral DNA wouldn't be very effective at replicating itself, would it?

Why are viruses organised the way they are?

Evolution.
Viruses, by the way, are quite varied in how they're organized.

Is the answer "No"?

Yes.


By the way, seeing as how your questions are basically all over the place, reading a textbook might be useful.
http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=mboc4.TOC&depth=10

It's not specifically about viruses, but it's about microbiology of the cell and that should give you a good start. You have to search for the particular chapter titles to get to them, the TOC isn't clickable. I know, a pain in the ass, but it's free.

 

[Asguard]

bilogically no a virus is not alive because unlike a bacteria it has no ability to replicate without a host cell

Does this make a difference?

Hell yes because it changes how we deal with virus's vs bacteria. For instance a virus can only stay "alive" for a set period of time in the air and so if you quarentine people with a virus you can concivably kill it off. This doesnt work for a bacteria because it can live on surfaces and reproduce forever as long as it has food

 

[invert_nexus]

Asguard,

For instance a virus can only stay "alive" for a set period of time in the air and so if you quarentine people with a virus you can concivably kill it off.

Viruses can survive quite a large amount of time in inert form, yes?

This doesnt work for a bacteria because it can live on surfaces and reproduce forever as long as it has food

Don't most bacteria die quite rapidly when removed from water? Some bacteria create spores in this extreme, but many (most?) don't have this ability. Dehydration is a death sentence to a bacteria.

 

[Asguard]

SOME virus can like antrax. Others like the HIV virus cant stay in the air for more than a few minutes

And as for moisture yes your probably right on this which is why food is dried to keep it longer. O2 can be essential or not depending on the paticular bacteria (for instance the anerobic bacteria which turn my NO2 into Nitrogen gas)

 

[Asguard]

oh there is also one more difference, you can GROW bacteria to find out what a pt is infected by but you CANT grow a virus to find out which it is (you have to use other techniqes like checking the pts antibodies)

 

[Roman]

SOME virus can like antrax. Others like the HIV virus cant stay in the air for more than a few minutes

And as for moisture yes your probably right on this which is why food is dried to keep it longer. O2 can be essential or not depending on the paticular bacteria (for instance the anerobic bacteria which turn my NO2 into Nitrogen gas)

Anthrax isn't a virus. Unless you really meant to type antrax. It's human immunodeficiency virus. The additional virus is superfluous.

And what are you going on about bacteria for? Viruses and bacteria are very, very different.


[edit]
My bad. There's been a bunch of ninja-posting.

 

[invert_nexus]

SOME virus can like antrax. Others like the HIV virus cant stay in the air for more than a few minutes

I wonder if there is one overriding difference between these two general categories of viruses?
I know that HIV has lipid envelope, could this be the cause? How many viruses do have lipid envelopes?

The virus I had in mind was the canine parvovirus. It, supposedly, can survive for years in its inert form.

 

[invert_nexus]

Anthrax isn't a virus. Unless you really meant to type antrax.

Derr.
Yeah.
Damnit, got me on that one.
It's a sporulating bacteria, yes?

 

[Asguard]

ops i could be wrong about that one. I thought it was virus spoors that live in the ground but it could be a bacteria (will check when i get home from work)

I DEFINITLY know that HIV has a short life outside the body because we did the statistics on it in epidemology. The HEP virus is slightly longer but again dies after a few hours

 

[Roman]

Yeah.
Interestingly, they're gram positive. Most pathogenic bacteria are gram-negative. Or maybe it's many species of gram-negative bacteria are pathogenic.

Wikipedia seems to make anthrax out to be a highly effective killer, but I dunno. It strikes me as an opportunistic or perhaps even accidental disease. Not very parasite like. Maybe opportunistic isn't quite the right word....

 

[Vkothii]

Another bunch of informative stuff, that says next to nothing. The answer is: "No", people.

Viruses don't always have DNA.

Whoa. Seriously? You mean some viruses have RNA instead?

Because that's how viruses work.

Viruses work? How come they work if they aren't alive?

If it didn't, who would? (By the way, it doesn't necessarily have to. Ever heard of shingles?)

I don't understand what you mean here with "who would". I have heard of shingles, yes. How do shingles illustrate why viruses carry their DNA (or RNA) around?

Floating viral DNA wouldn't be very effective at replicating itself, would it?

Why not?

Evolution.

Ah, Evolution does it. Good old Evolution, huh? Thank God that's available as a catch-all, then.

Viruses, by the way, are quite varied in how they're organized.

Yes, I know.

 

[Roman]

Viruses work? How come they work if they aren't alive?

How come fires burn if they aren't alive? How does that work? How does ice form complex structures if it isn't alive?

Do you know why viruses fail to be defined as life? Because I think this may be the source of your misunderstanding.

You're assigning the property "does mysterious stuff" to life, and "doesn't do mysterious stuff" to non-life. A bacteria does mysterious stuff, yet isn't considered alive.

How could this be?

Because your definition of life differs from the criterion used for evaluating viruses.

 

[invert_nexus]

You mean some viruses have RNA instead?

Yes.
Different types of DNA as well.

Viruses work? How come they work if they aren't alive?

Sigh.
Still stuck on semantics.
Does your car work?

I don't understand what you mean here with "who would".

I'm using who to denote an entity which would do the carrying. In this context, the virus would also be a 'who'.

I have heard of shingles, yes. How do shingles illustrate why viruses carry their DNA (or RNA) around?

It actually illustrates how viruses don't have to carry around their own DNA. Retroviruses insert their genetic code into a living organism's genetic code. Shingles are an outbreak caused by this inserted code, not by a new virus infection.

We carry around quite a few viral remnants in our genetic code.

Why not?

Well, for one thing, free floating DNA would be denatured quite rapidly, unless I'm mistaken. It also wouldn't really be able to get past the cell membrane and into the cell, except as food, which wouldn't really help in replicating itself.

Ah, Evolution does it. Good old Evolution, huh? Thank God that's available as a catch-all, then.

Your problem is in asking why. Viruses are organized as they are because they've evolved to work in that way. They've evolved through various selective pressures. If you had the facilities, you could probably spend some time examining the evolutionary history of a single virus and be able to tell a story about the selective pressures which led to its present operating mechanism, but this would be a difficult job.
Interesting though.

What's wrong with the answer?

Yes, I know.

Then why did you ask?

 

[Roman]

We even have self-replicating pieces in our genome that move around- transposons and retrotransposons- that don't seem to serve any function. In fact, they may be deleterious, and other elements of the genome evolved (such as methylating DNA) to circumvent insertion of transposons in coding regions.

 

[Vkothii]

Viruses are organized as they are because they've evolved to work in that way.

Doesn't that conflict with the idea that viruses aren't alive?
You haven't distinguished between a working virus and a living organism either. A car works because an agent uses it.
So what uses a virus?
How does a retrovirus insert DNA as genes into a host? Or does the cell do this, and if so, why?
I thought retroviruses had copies of reverse transcription enzymes that did this?