   lifeforms without DNA?
  Do there exist lifeforms on Earth that don't use DNA? Are there alternatives to DNA?Isn't it weird that trees and animals are so different and have never had any sexual contact for a billion years (duh), and yet still both have DNA? A billion years of evolution has generated so many different kinds of lifeforms, yet the DNA system itself is still about the same with the same base-4 numbering system and the same molecules.   
Yes (RNA viruses use RNA), and yes there are alternatives.;  Umm... I think the whole DNA mechanism evolved before there were multicellular organisms, let alone a distinction between 'plants' and 'animals'. Also, sexual reproduction is not required for DNA to be useful; evolution still works without exchange of genetic material, it just does so significantly slower (think picking up random pieces of paper to try and obtain a particular baseball card, as opposed to swapping cards with someone else. In the second instance at least you're likely to get cards rather than parking tickets or random junk, so your chances of getting the card you want are increased dramatically).Oh, and as for the whole no-DNA thing, I'm fairly sure there are. Those RNA virus thingies are arguably not alive (or 'only sorta' alive) but I'm sure I heard about some (very primitive) single-celled organisms that don't use DNA... of course it could be my brain making things up again. :/   ;  Unless of course you consider viruses to be machines or otherwise "not alive", which some Biochemists do.. But thats a whole other conversation.EDIT: an example of an RNA virus is HIV (both 1 and 2). These organisms use RNA as an evolutionary mechanism to increase their mutation rate, which is why they become immune to drug treatments so quickly.   ;Quote:Original post by LodeDo there exist lifeforms on Earth that don't use DNA? Are there alternatives to DNA?Isn't it weird that trees and animals are so different and have never had any sexual contact for a billion years (duh), and yet still both have DNA? A billion years of evolution has generated so many different kinds of lifeforms, yet the DNA system itself is still about the same with the same base-4 numbering system and the same molecules.Prions, the widely accepted infection agent of Krutchfeild-Jacob disease (aka Madcow, scrapie) are proteins that influence other proteins to become prions.  They're less life like than virii.Trees and animals do have sexual contact? (You must mean across species or something). Soil bacteria absorb dna from their environment and incorporate into their genome.  This was the basis for early work in recombinant dna work.The genetic code HAS changed over 100's million years.  Some nucleotide bases can be used in place of others and some amino acids are specified in the code that weren't specified in the past.   ;Quote:Original post by fractoidUmm... I think the whole DNA mechanism evolved before there were multicellular organisms, let alone a distinction between 'plants' and 'animals'. Also, sexual reproduction is not required for DNA to be useful; evolution still works without exchange of genetic material, it just does so significantly slower (think picking up random pieces of paper to try and obtain a particular baseball card, as opposed to swapping cards with someone else. In the second instance at least you're likely to get cards rather than parking tickets or random junk, so your chances of getting the card you want are increased dramatically).Oh, and as for the whole no-DNA thing, I'm fairly sure there are. Those RNA virus thingies are arguably not alive (or 'only sorta' alive) but I'm sure I heard about some (very primitive) single-celled organisms that don't use DNA... of course it could be my brain making things up again. :/If you read Richard Dawkin's "The Blind Watchmaker" that is exactly what he suggested. He even gave example of processes that might have resulted with complete DNA mechanism because, let's face it, DNA mechanism is to complex to spring up overnight.   ;  Also consider mitochondrial dna.   ;  Here's something on the more controversial possibly pseudoscience end of things:  Dr. Godfery Louis, a physicist, studied a phenomon of red rain in India, and determined through his own research and studies that a meteor (see his first paper) burst high up in the atmosphere, and released a massive amount of dormant spores, which over a two month period slowly sank into the lower atmosphere and mixed with clouds to cause the red rain.  The spores (see his second paper), when heated to really hot temperatures (think 300 degrees Celsius), became active cells and multiplied, using a wide variety of resources in order to do so.  He could find no evidence of DNA in these cells.I have yet to find any information that is conclusive from any source other than Dr. Louis, who specializes in crystals, not microbiogy.  I found plenty of news articles saying that certain scientific organizations obtained samples of the spores, had done preliminary studies, and that the precise species had not yet been identified, and that they had no idea how so much got into the clouds.  Basically, from official sources, all I got was incomplete and vague information.  It's a rather curious occurrence, if nothing else.   ;Quote:Original post by jonpolly99Unless of course you consider viruses to be machines or otherwise "not alive", which some Biochemists do.. But thats a whole other conversation.EDIT: an example of an RNA virus is HIV (both 1 and 2). These organisms use RNA as an evolutionary mechanism to increase their mutation rate, which is why they become immune to drug treatments so quickly.Viruses have no metabolic processes, so they are (by the biological definition) not alive.  Viruses are basically little pieces of nucleic acid polymers that can be DNA and/or RNA.  RNA is not really used as an "evolutionary mechanism" in the HIV viruses.  The RNA found in retroviruses (like HIV) uses reverse transcriptase found in the host to construct DNA...which does the actual damage.The reason why RNA is linked to evolution is because, being single standed/having the ability to oxidize phosphate groups, etc...its not as stable as DNA and is prone to mutation...mutation usually comes in the form of favourable change.I dont think that there are any living being that dont at least possess some form of nucleic acid as their main "information source".   ;Quote:Original post by AgonyOMG IT WAS TEH RED WEEDZ! SAY YUOR PRARES POPPET, TEH MARTIANS ARE COMEING!!!1!!!`ffx - No, I haven't read that yet, but it's definitely on my to-read list. I've always been interested in evolution (both simulated and actual) - one thing I'd really like to see at some stage is a simulated 'ecosystem' that develops speciation on its own... obviously it has to have all teh pwetty gwaphics too because early attempts (like framsticks) look fugly. :)   