"Extraterrestrial Life May Not be Based on DNA or RNA" --New Research (Today's Most Popular)
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April 28, 2012

"Extraterrestrial Life May Not be Based on DNA or RNA" --New Research (Today's Most Popular)

 

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Synthetic biologists have discovered that six other molecules  can could store genetic information and pass it on. A host of alternative nucleic acids have been made in labs over the years, but no one has made them work like DNA. Until now, everyone thought we were limited to RNA and DNA. This is the first time artificial molecules have been made to pass genes on to their descendants. The finding is a proof of principle that life needn't be based on DNA and RNA. 

The ability to copy information from one molecule to another is fundamental to all life. Organisms pass their genes to their descendants, often with small changes, and as a result life can evolve over the generations. Barring a few exceptions, all known organisms use DNA as the information carrier."This unique ability of DNA and RNA to encode information can be implemented in other backbones," says Philipp Holliger of the MRC Laboratory of Molecular Biology in Cambridge, UK.

Holliger's team focused on six XNAs (xeno-nucleic acids). DNA and RNA are made of a sugar, a phosphate and a base. The XNAs had different sugars, and in some of them the sugars are replaced with completely different molecules. Synthetic XNA, with its different sugar backbone to natural DNA, can mimic many of the properties of the real thing.

Holliger and his team engineered enzymes that helped the six types of XNA to assemble and replicate genetic messages. The enzymes transcribed DNA into the various XNAs, then back into new DNA strands — with 95% accuracy or more.

A major challenge for the team was to create enzymes that could copy a gene from a DNA molecule to an XNA molecule, and other enzymes that could copy it back into DNA. Once they had created these enzymes, they were able to store information in each of the XNAs, copy it to DNA, and copy it back into a new XNA. In effect, the first XNA passed its information on to the new one – albeit in a roundabout way. "The cycle we have is a bit like a retrovirus, which cycles between RNA and DNA," Holliger says. Because the XNAs can do this, they are capable of evolution.

Genetic transmission over successive DNA-to-XNA cycles allowed researchers to select for only those XNAs that attached to certain target proteins from a pool of random samples — a process akin to evolution over multiple generations.

“For the first time, this confirms that replication, heredity and evolution are possible in these alternative backbones,” says Holliger.."This is very interesting with respect to the origin of life," says Jack Szostak of Harvard University in Boston, Massachusetts. Many biologists suspect that the first life-forms used RNA, and DNA was adopted later. But we don't know why those two molecules were chosen: are they the best possible storage media, or were they simply the only things available?

Holliger suspects RNA was an opportunistic choice. "Clearly, there is no overwhelming functional imperative to use DNA and RNA," he says. Instead, life may have started with RNA simply because it was made in large quantities on the early Earth.

Most biologists think life on Earth began with RNA because it can both store information and catalyse useful reactions. In his latest experiment, Holliger has now shown that one of his XNA's – 1,5-anhydrohexitol nucleic acid, or HNA – can fold into a 3D shape and bind to specific target molecules. This is the first step in becoming an enzyme. The same thing had previously been done for threose nucleic acid (TNA).

This suggests XNAs might form the basis of life on other planets, where different environments led to different chemistry. "I would be surprised if we find truly extraterrestrial life that was based on DNA and RNA," Holliger says. "There might have been an XNA-world on a different planet."

The Daily Galaxy via newscientist.com, science, nature.com and Nature doi:10.1038/nature.2012.10487 and Journal reference: Science DOI: 10.1126/science.1217622

This post was the most popular posted on the Daily Galaxy during the past seven days.


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Comments

Yeah Right! So scientists on other planets create synthetic DNA and RNA! Absolute proof of life elsewhere! Editor's Note: Hey Matthew, read the post....it doesn't say it's proof of life elsewhere. They're saying that it may not be DNA/RNA based.

Hmmm, the above post is proof positive, if indeed it were needed, that not all life on earth with respiratory functions is intelligent...

Hmmmm..., Life elsewhere? Hah! Fat chance! I personally bet the odds are a BILLION to ONE that any star could possibly have a suitable planet. Do the math!
Over a hundred billion stars per galaxy, and at least a hundred billion galaxies. So at that pathetic rate there could only be about...let's see...about 10,000,000,000,000 stars in this universe with life. Just TEN TRILLION! See there. That's hardly any life at all!

I always imagined that there are MANY ways for life to form, we just have our version of life due to the elements we have. I think it's silly when people say aliens will look like us, fat chance I say, we won't even recognize them as aliens most likely.

About time scientists faced the true facts.
Great article. Pay no attention to convention.
I am sure every star knows more about life and true facts than us mere humans.

And please, how can humans just think of a star as a chemical furnace - people, you shall learn from me if need be - stars are alive with emotion. Star are aware.
Stars are moleculer and form configurations so as to perform a certain physical function.

This DNA is earth evolved - may not of originated from earth.
may have been seeded accross the cosmos and other genetic molecules will be.

If this is the case, the habitable zone around stars is much larger than what was thought to be the case. Even moons like Saturn's Titan would fall into the habitable zone around a star.

No, everyone did NOT think life was based on DNA or RNA...only people who are so narrow minded as to think all life is similar to that of one teentsy lonely planet, out of 10 to the 1000th power of planets called Earth. Some form of complex molecule would be present in E.T. life alright but not necessarily anything resembling RNA or DNA.

The fact that complex molecules form first which can replicate themselves, is a precurser of life on any life planet, is plausible.

I have to laugh at some of the ET cultists who think ET DNA and ours can be mixed to make an ET/Human hybrid. If they knew anything about anything involving how genetics work and why, they would never utter such a preposterous statement. I'm not talking about ETs maniupulating human chromosomes, I'm talking about the impossibility of mating or combining human DNA with 'their' DNA and coming out with a hybrid. Won't happen.

I'd say each life planet has its very own particular way of doing things involving transmitting inheritance code from one generation to another. Yes, there will be similarities to Earth life et al but not exactly the same.

The ET cultists say that some people and some abductees have seen "Arians", tall blong haired fair skinned beings closely resembling humans who are from the Pleiades star group. IF this is true, then morphologies can be similar but NOT their inheritance code. Yes, other beings could have similar molecules to our RNA and DNA but not exactly. Those molecules are so immense that it would be almost impossible to have compatible DNA or RNA as Earth life has.

As to how life forms on other planets accomplish inheritance is up for grabs as we have no base on which to even think about it, other than, yes, there would have to be very large complex molecules involved which serve as inheritance code.

Life on Earth reprocreates using two methods. One, sexual. Sexual means sperm/egg. Two, Asexual means with sperm/egg but not sexual contact such as plants (pollen from a stamen delivers sperm cells via a tube in the female flower part, to the ovary of the flower). Three, then there are ferns. Four, Division/mitosis is yet another form and if you want to count viruses recoding a cell's DNA to produce more viral DNA, then producing on it's cell wall an RNA coat for the newly formed DNA, then count that as number five as well. A large organism such as a planaria divides and earth worms and some reptiles can change sexes. Life has a way of reprocreating or it would not be life.


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