There are several good examples of non-DNA based inheritance /understand transmission of biological information/ even on earth:

- multplication of prion proteins

- transgeneration inheritance of chromosome structures, such the centromeres

- there are reports of DNA-like molecules containing arsenic atom in their backbone instead of conventional phosphorus in certain microorganisms living in metal-rich lakes.

The view of DNA as the only information molecules is not correct from the evolutionary point of view. We already know that the first sefreplicating molecules were based on RNA rather than DNA. As time passed, DNA replaced  RNA from complex structures so the present life is virtually based on DNA. There is no doubt that DNA will continue to evolve. One can only imagine how the information molecules of living organisms will look like after a billion of years. Certainly, they will be different from what Watson-Crick-Franklin observed.   

I think it's very difficult to speculate on some of those questions as we only have one data point: us. Having said that, Adam Rutherford covers this topic veru well in his book Creation.

This seems like an exercise in futility.   Nevertheless, it would seem that any chemical polymer structures that can serve as a template for its own replication and also encode information in a combinatorial coding manner could form the basis of life.  If we start thinking about other non-protein based life forms - I am not even sure how to envision such things -  then it become even more speculative.

Look at this http://en.wikipedia.org/wiki/Threose_nucleic_acid  & http://en.wikipedia.org/wiki/Peptide_nucleic_acid

You could take a look at the "RNA world" hypothesis. Some people certainly agree that DNA is not the only possibility.

There has been work done that shows that DNA with only 3 bases, and even only 2, can be used to faithfully transmit informaiton; so there's no reason to assume that even if it was DNA-based that it would have to be exactly like ours.

Also genetic code evolved, so if on any other world we would find organism with similar genetic code (there are some small differences even on Earth) it will be proof of same origin.

Certainly, Chargaff's second parity rule will pose a very severe constraints to the number of possible genetic code. Second, one of the main theory of interaction has been called the Mekler–Idlis (M–I) pair theory. According to this theory, sense–antisense peptide interactions are made possible by inter-peptide contacts between the side-chains of sense peptide codon-directed amino acid residues and corresponding antisense (complementary) codon-directed amino acid residues in the antisense peptide. This theory actually is direct consequence from Chargaff's second parity rule.

The strands in duplex DNA are anti-parallel and I think this is the key element in understanding the possible structures of hereditary systems. 

Murat Saparbaev - it is true, but only on Earth :-) 

We may suspect that simple organic substances (amino acids, sugars etc.) can be used elsewhere, but higher levels of organization do not have to have anything to do with ours. Of course, unless they come from the same ancestor.

There are several good examples of non-DNA based inheritance /understand transmission of biological information/ even on earth:

- multplication of prion proteins

- transgeneration inheritance of chromosome structures, such the centromeres

- there are reports of DNA-like molecules containing arsenic atom in their backbone instead of conventional phosphorus in certain microorganisms living in metal-rich lakes.

The view of DNA as the only information molecules is not correct from the evolutionary point of view. We already know that the first sefreplicating molecules were based on RNA rather than DNA. As time passed, DNA replaced  RNA from complex structures so the present life is virtually based on DNA. There is no doubt that DNA will continue to evolve. One can only imagine how the information molecules of living organisms will look like after a billion of years. Certainly, they will be different from what Watson-Crick-Franklin observed.   

Ales Kovarik nice answer.. but I've tried to follow this topic:

"there are reports of DNA-like molecules containing arsenic atom in their backbone instead of conventional phosphorus in certain microorganisms living in metal-rich lakes."

The current status of that research is that everything was a measurement mistake, see the Wolfe Simon Controversy. Although her findings couldn't replay, they team haven't retracted still

Hi Aimer, thanks for the update of arsenic DNA. It is worth following these mysterious molecules, anyway.

Interesting topic. 

http://ac.els-cdn.com.ucd.idm.oclc.org/S0022519399910457/1-s2.0-S0022519399910457-main.pdf?_tid=83fefb7c-3cbf-11e4-bc54-00000aab0f6b&acdnat=1410775577_8e3de983d85baacadeb611da8269176c

http://www.biologydirect.com/content/pdf/1745-6150-2-14.pdf

http://www.biologydirect.com/content/pdf/1745-6150-2-24.pdf

I would also like to extend my question; not relevant to Steven's question

Is there way out to disapprove DNA evolution using information given in DNA or might be any other way?

How did we prove that the first sefreplicating molecules were based on RNA rather than DNA? Is it a plausible theroy or more than that?

Muhammad that question would be in the main menu

The hypothesis that the first selfreplicating molecules on earth were RNAs stems from observations that some RNA molecules of highly specific structure exhibit the capacity to replicate themselves and also other RNAs. To my best knowledge this autocatalytic property has not been detected in any kind of  DNA. More in Wikipedia and related links.

i have to imagine that life has had ample opportunity to arise right here on earth using different information-containing, self-replicating molecules, but the only successful forms of life have clearly been RNA/DNA-based systems. Perhaps RNA/DNA systems out-competed others, or there really aren't other systems upon which complexity can build, at least with the composition of elements we have to work with on earth. The RNA to DNA transition in information storage happened because DNA polymers are much more stable than RNA polymers due DNA's lack of the hydroxyl at the 2' pentose position, which makes RNA prone to hydrolysis. 

Hello Emma, et al.,

Thank you. Since the discussion is getting into hypothesized ancestral information-transmission systems on this planet, it seems worthwhile to highlight the suggestion that even RNA is far too complex to be the ancestor. This critique, and an alternative suggestion about the kind of system that might have been simple enough tumble together by laws of physics and chemistry alone (and yet still serve as both a unit of heredity and a target of selection), has been offered by A. G. Cairns-Smith, for example here:

DOI: 10.1002/chem.200701215

Dr. Jack Szostaks lab has been doing research for a long time on simple replicating vesicles with nonenzymatic RNA synthesis inside these model protocells http://molbio.mgh.harvard.edu/szostakweb/index.html, their articles might be of interest for you. And yes it is indeed widely believed that RNA came before DNA because DNA, unlike RNA is rather inert, but RNA can catalyze it's own transformations, including the addition of novel monomers and replication. Actually if you look inside the ribosome you will find that RNA is present in the catalytic centers while the ribosomal proteins provide something like a "carcass" that help the RNA molecules to perform protein synthesis. Perhaps even RNA-protein came before DNA, but that is debatable. Speaking of hypothetical alternatives to DNA-RNA and even carbon-based forms of life there is an article in wikipedia http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry that might provide some interesting information on your question. For example the possibility of silicon-based life forms is discussed.

The idea that there might be alternatives of replicating information molecules that are not dependent on nucleic acids is certainly exciting. However, whether they are based on silicon polymers /suggested by Sasha/ or self-replicating crystals /referred to by Steven/ they, unlike to RNA, never evolved to become molecules of life. Perhaps, interactions with other molecules such as short peptides, lipids were needed to establish primitive metabolically active entities. When considering RNA complexity, one has also bear in mind that the non-cellular phase of life evolution lasted one billion years. Certainly, this long period enabled formation of thousands of RNA molecules of different sequences, modifications, bases and lengths.  By selection, only some of them survived and continue to evolve. Evolution is a tinker not an engineer.  Now it comes to an uneasy and highly debatable definition of “what is life”. It may well be that human beings suffering from anthropic behavior are too blind to the speech of non-carbon life though it may have existed on earth or even still exits.  

It may be interested for you:

What is Artificial Life?

Christopher G Langton

Editor of the Artificial Life journal

http://www.biota.org/papers/cglalife.html

http://en.wikipedia.org/wiki/Christopher_Langton

http://en.wikipedia.org/wiki/Christopher_Langton

http://www.biota.org/papers/cglalife.html