Exception to Characteristics of Life.

[Poison]

Are robots made of organic material? Or do they carry DNA or RNA? No. But viruses do. Dont they?

[biostudent84]

Viruses carry RNA, true.

But viruses are not made of cells, a stipulation clearly stated in the modern accepted definition of life.

If you want to call viruses life, then you must first confront the entire biological community to petition for the definition of life to be changed. Or at least redefined.

[Poison]

If you want to call viruses life, then you must first confront the entire biological community to petition for the definition of life to be changed. Or at least redefined.

I'm not trying to call viruses life. I just want someone to persuade me.

[canalon]

Hello,

Virus can carry both RNA or DNA, but it cannot self replicate, it needs a cell replication mechanism to copy and multiply its genetic materia and to synthesize its enveloppe. They are basically genetic material wrapped in a membrane, without any machinery.
Prions do not carry genetic materials, they are proteins that change the folding of normal proteins (produced and coded by a cell) into the pathogenic form in self catalytic process.

Are they alive The limit is hard to draw.

If it was not for the "made of cells" conditions, crystals could have been a good answer, they grows using only free material in the environment, without the need of a complex external machinery (i.e. a cell). And they are indeed making new copies of themselves. They were even supposed to have been one of the possible origin of life, though it is note the most highly favoured. And they are definetly non liveng entities.

HTH

Patrick

[Moff231Dawrin]

you know, trus, you might want to ask your biology teacher that one. It would be interesting to see what he/she thinks. Also, did you get that quiz back yet?
That's a good question, and as far as I can tell, a Virus is as close as it comes. the next thing I'd guess is prokaryotic cells, but those have DNA. I'm curious to find out, so if you get any idea as to what it might be, please tell us.

[Poison]

Thank you all for your explanations. Now they really seem to me like non-living.
But I have one more question. (I think I asked it before). Can 'respiration' be the point where living and non-living differ? (I mean the exact point)

[biostudent84]

While it is not included in the actual definition of life, I would have yo say yes, you might be right on that one. It would be hard to judge unless we can find a packet of chemicals that undergoes respiration but fails to meet the parameters of life...or one that does meet said parameters, but fail to respire.

[Moff231Dawrin]

that's a little but of an paradox, isn't it? after all, don't living living things need to be able to go under respiration for energy? so how can something live and not undergo respiration? It's like what they say, "When you breathe, you respire. When you don't breathe, you expire."

[Maxwell]

Viruses are not considered to be alive for two reasons:

1) They do not produce their own energy
2) They cannot reproduce on their own. They need the help of a host cell's machinery to produce more viruses.

Viruses also cannot be the answer to the riddle because, as stated by biostudent, they are not made of cells. Additionally, all viruses have some sort of genetic material in the form of either RNA or DNA depending on the virus. The RNA or DNA can be either single or double stranded.

[RobJim]

I don't see any way for this to have an answer and not be a trick question. All cells that grow and reproduce have RNA at least. I'm not sure if there's any true life without DNA, but if so it will have RNA.

The answer could be something like a beehive, but the bees have DNA and RNA and are essential for the reproduction and growth...it sounds like a trick question of some kind.

[thank.darwin]

Right... can any living thing replicate without RNA or DNA?

[biostudent84]

Right... can any living thing replicate without RNA or DNA?

Actually, yes. DNA sequencers do it all the time.