It is most probably RNA, that is because it is the only known types of biomolecules that exhibit both catalytic and informational activity.

As you might have been read all expertise has commented. DNA is first as it is give birth to RNA by the process of transcription and the RNA only work as a cassete to be readed for protein formation by process of translation. you also have a point that why not RNA first as it can also reverse transcript? but the basic difference is that themolecular weight of RNA is much lower than DNA....

It is may be RNA because RNA can also act as genomic material in some organisms. without DNA also they grow and replicate themselves. in evolution these organism are came first.

Mr. Rajender, surely RNA was first as if you observe the chemical composition of RNA and DNA, 'URACIL' U present in RNA where as THYMINE' 'T' is in DNA. sure u canclearly understant the difference between the U and T where the 5th position of U is filled with CH3 group by doing so it converted to T. Due to some mutations this change was happened. so, DNA came from RNA..... I think this explonation is an exact answer for your question.

Protein was first. Alexander I. Oparin dixit.

By Biology Dogma, DNA was the first

Thomas Cech was awarded Nobel Prize in 1989 for stating that life could have started with RNA as RNA could itself cut strands of RNA.

I think RNA is first. The typical example is ribozyme, it's RNA, and have catalytic activity

We must expand our view of life. Remember that was recently published a paper on inorganic life.

I recommend reading this article in order to answer the question.

Wiley Interdiscip Rev RNA. 2010 Sep-Oct;1(2):202-13. doi: 10.1002/wrna.37. Epub 2010 Jul 16.

"RNA in evolution". Lehman N.

(...) "In particular, the finding that RNA can be catalytic, and thus possess both a genotype and a phenotype, has forced us to consider the possibility that life's origins began with RNA, and that the subsequent diversification of life is aptly described as a string of innovations by RNA to adapt to a changing environment. Some of these adaptations include riboswitches, ribonucleoproteins (RNPs), RNA editing, and RNA interference (RNAi). Although many of these functions may seem at first glance to be recent evolutionary developments, it may be the case that all of their catalytic activities trace their roots back to a primordial 'RNA World' some four billion years ago, and that RNA's diversity has a continuous thread that pervades life from its very origins"

Another point to consider is that short RNA "primers" are required for DNA replication both in vitro and in vivo. The enzymes involved in replication may therefore have evolved first for an RNA substrate and template. Chemical modifications to both ribose and uracil (one deoxygenation, one methyl substitution) are plausible reasons for RNA to be the first molecule of heredity. As previously noted, RNA also has catalytic activity and serves as the sole genomic material for many viruses. I'm also very intrigued by Joy Sinha's comment about riboswitch--any suggested readings?

Joy: That's fascinating! New things to learn! Thank you for sharing that reference--it's a good starting point.

i think RNA . because RNA have enzyme activity ( ex : telomerase ) and also RNA can transport information to next offspring ( ex : virus , some bacteria ).

i also believe that RNA evolved first. RNA had the ribose sugar where as DNA had the deoxyribose sugar, which might have formed from the previous.

Well RNA is first. due to a variety of reasons DNA later took the center stage of being a genomic material. Its deoxy group at the 2' position made it much less sterically hindered as compared to RNA and another reason is there. If one really wants to know the details and other proposals that had been made, one can read the Review Article- The Antiquity of RNA based evolution

It's a contoversial statement though if one compares RNA and DNA properties. it is easy to assume RNA comes first and DNA later on but this logic lacks strong evidence support...............as we all know DNA or RNA alone or together cannot give rise to a LIFE, there is a complex interplay between other biomolecules also which finally makes the environment essential for the origin....................in view of existence of reducing atmosphere on Earth and it's gradual entering into modern world, I expect protein to come first, followed by RNA and then DNA in last.

such evidence of protein coming first may be there but I havent come across it, researchers had also proposed existence of Threose Nucleic acid that is TNA...bt right now, Sydney Fox's theory is the accepted one....

I think according to central dogma of molecular biology we get first DNA from replication then transcription and then translation.

i think RNA frist as it is more simple in structure than DNA (single stand) and it can act as genetic material in procaryote and in some viruses according to Evolutionary theory

Hi everybody. I think that this is a hot topic. Perhaps is RNA the first nucleic acid that appeared in LIFE. For example, the ribosome is one of the most ancient molecule in our cells. Furthermore, ribosome is composed of RNA and protein (Ribonucleoprotein) and if you eliminate the majority of protein content you could maintain the protein synthesis. So, RNA is the most important part of the macromolecule and this observation is in agreement with the knowledge of ribozymes, RNA with a autocatalytic capacity.

Hi,i think that DNA IS first..RNA is later because RNA needs DNA strand for its synthesis..

it is the egg and chicken causality dilemma. Because it is a circular cause and consequence.

we spin like a dog around tail. We don`t have to much info about secret of life on earth. Beyond this we need to know exactly our position in universe. When you see from the cave what happens outside you can make a lot of prediction but you can`t see the mountains, the river, and the big ocean. So,Alexandra, be patience and all answer will be come.

God only knows the secret of the beginning of life

joining of base pairs requires enzymes (proteins) ........................ there has to be one master gene for all the life forms taken together........... and its associates (some proteins ....) ... ancient literature who r more close to the origin of life term this as the god..... and his associates... :) The World of Biologists who r looking for the secrect of life should travel back in time ..... but with each day passing by they will be one day lagging behind evolution....... no hope of finding the secret of the master gene which is engineering this world. we r evolving from lower forms or into lower forms ....... cant say what our ancestors were capable of we can predict their physical ability but can their mental ability be predicted......? Only if we know what we r changing into we can understand the perfomance of this world..........

It is RNA first . Because we know about the central Dogma and the RNA world

The article in science 8 april 2011 about ribozyme may give an answer to such a question

I think the first is DNA.RNA is very unstable than DNA and conversion of RNA to DNA needs more enzymes and energy

I believe it started of with a single stranded DNA

RNA World approach is a possible solution for the evolution of RNA before either proteins or DNA because RNA combines some of the features of proteins and DNA. RNA can catalyze chemical reactions just like proteins, and it can store genetic information just like DNA. And, the cellular machinery that uses RNA to synthesize protein is made partly of RNA and relies on RNA to do its job. This suggests that RNA might have played a crucial role in the early history of life.

Experiments in the 1960s showed that messenger RNA has the ability to store genetic information, while transfer and ribosomal RNA have the ability to translate genetic information into proteins. Experiments performed two decades later showed that some RNAs can even act as an enzyme to self-edit their own genetic code! These results raised two questions: 1) Why does RNA play so many roles in the flow of genetic information? 2) Why bother storing genetic information in DNA, if RNA alone could do the job?

RNA has great capability as a genetic molecule; it once had to carry on hereditary processes on its own. It now seems certain that RNA was the first molecule of heredity, so it evolved all the essential methods for storing and expressing genetic information before DNA came onto the scene. However, single-stranded RNA is rather unstable and is easily damaged by enzymes. By essentially doubling the existing RNA molecule, and using deoxyribose sugar instead of ribose, DNA evolved as a much more stable form to pass genetic information with accuracy.