From DNA to XNA: The Possibility of Life Not as We Know It
Scientists claim they've induced some exotic DNA relatives to evolve.
From DNA to XNA: The Possibility of Life Not as We Know It
The relevance of evolution to the origin of life came up in the comments following yesterday's post. That may not be a coincidence, since I had been working on this piece at the time and talking to scientists who envision the origin of life as an evolutionary process. How could "chemical slop" become life? A closer look reveals that some chemicals are not as sloppy as they appear to the untrained eye.
This column will also a appear in Monday's Inquirer:
Blurring the lines between life and inanimate matter, biologists announced today that they’d created six different chemical alternatives to DNA and coaxed them to undergo evolution.
A description of these code-carrying molecules, called XNAs, was published in the journal Science. The work bolsters a prevailing hypothesis that life as we know it evolved from simpler life forms, no longer here, and those evolved from something simpler. There may be no moment when the first life emerged, but instead an evolutionary process by which chemicals that most of us would consider non-life gradually gave rise to living cells through natural selection.
The work on XNA molecules adds to a growing field of test-tube evolution, in which scientists are nudging code-carrying chemicals to evolve into drugs or other useful compounds.
Scientists don’t have a universal definition for life, but they do agree that to qualify as life, an organism must be subject to natural selection. All life on Earth is related and uses the same basic building blocks, but life elsewhere might be put together differently, challenging scientists to recognize it. NASA defines life very broadly, as any self-replicating system capable of Darwinian evolution.
Biochemist John Chaput, one of the authors of the XNA paper, said evolution can happen in a molecule as long as it can carry a code and copy itself with a few errors. At that point you have something capable of heredity.
Such chemicals might be commonly thought of as primordial soup but on a molecular scale they are highly organized.
By most definitions, including NASA’s, these XNAs aren’t alive because they need help to replicate. Gerald Joyce, a researcher at the Scripps Research Institute in La Jolla, said that’s why he saw no particular danger at this stage. If someone spilled a flask of XNA molecules on the floor or down the drain, the molecules couldn’t multiply or infect living things. They can’t feed off our biology.
Joyce, who wrote a commentary piece accompanying the scientific paper, said there’s more danger in making novel organisms with traditional biochemistry, which could potentially interfere with living things. “This is more radical but less dangerous,” he said of these XNA molecules. “It’s outside our biology.”
Like DNA, these XNA molecules string together four different chemical units into long chains – thus carrying a code in four-letter alphabets. In DNA, the four chemical units are called bases and are identified by the letters A, T, C and G. Those are attached to a backbone or scaffolding, which in DNA are made from sugars and chunks called phosphates. The XNAs use the same characters - A, T, C, and G - but the backbones that hold them together are different.
Scientists suspect that DNA evolved from a simpler cousin called RNA. DNA comes as a double strand of code twisted into a spiraling ladder, while RNA is a simpler single strand. But RNA is still a complicated molecule, and so scientists studying it suspect it came about from a simpler precursor that no longer exists in nature.
Chaput, who works at Arizona State University, was involved with one of the XNAs called TNA, which has a simpler structure than either RNA or DNA. While the TNA isn’t alive, it can be induced to undergo evolution, he said. In his lab, he pushed TNA molecules to evolve the ability to do one simple task – to stick to a particular protein. That’s something molecules called receptors do in our bodies.
Scripps’ Joyce says one interesting property of the XNAs is they’re more durable than ordinary DNA or RNA. XNA’s don’t biodegrade, since they are outside our biology and can’t be eaten or broken up by enzymes associated with life as we know it. With RNA and DNA, researchers have to wear gloves to keep from destroying these fragile molecules, but with XNAs that’s not necessary.
That ruggedness might make XNAs useful for fishing out specific DNA sequences in genetic tests or other diagnostics, or for detecting contaminants in the environment. Chaput said they could be particularly important in a growing field of medicine in which scientists prompt chemicals to evolve into new drugs. Scientists refer to such evolution-derived drugs as aptamers. One, called Macugen, has already received FDA approval for the treatment of an eye disease known as macular degeneration.
Joyce, who is a fan of the Arthur C. Clarke novels 2001 and 2010, sees the fictional planetary explorations as a metaphor for the power and danger that would come if scientists someday created XNA-based life.
In 2010, astronauts discover life on Jupiter and Europa, and while humans are tempted to explore and exploit Europa, the computer, Hal, warns humanity to attempt no landings there, presumably because our life would contaminate and destroy theirs.
In this case the danger would be to Earth. Scientists, Joyce wrote in his commentary piece, “are beginning to frolic on the worlds of alternative genetics, but must not tread into areas that have the potential to harm our biology.”
Contact Faye Flam at 215-854-4977, fflam@phillynews.com, or @fayeflam on Twitter. Read her blog at philly.com/evolution.
How could a flying arrow appear to be standing still in a photograph and being in Movement at the same Time?
The arrow seems to exist in one dichotomy of Time.
In fact, this dilemma reveals the existence of two different dimensions, one seemingly in evolution and marked by the rhythm of Time and also One other which is in Stability and transcends our dimension.
The snapshot captures the essence of this other Dimension existing beyond Time, Space and Movement.
For example, you are now one Existence different than you are .... now.
The change of Existence (or evolution) occurs instantly.
What we ordinarily think of as the same object, persisting through Time, is in fact a succession of different objects (though very similar), each unchangingly set into their own present moment.
On each moment there is a different object or a different person.
This also eliminates the concept of Time for any sort of Existence.
This new conception could result to be puzzling because even though we seem to persist through Time each of us is never the same.
In this perspective from a different dimension, if there is no change for us, then, what does death amount to?
As incredible as it may seem, such event will amount to one other instant lived by a different person than .... you are .... now.
www.wavevolution.org
— wavettore- RE: DNA/XNA
"scientists are nudging, they need help to replicate, it can be induced to undergo evolution, pushed to evolve, prompt chemicals to evolve" ----- read ID?— Jack29 - The story of molecular replication is one reason why I think that it's wrong to talk as though evolution is entirely separate from the origin of life. Nevertheless, there's certainly more to the story of abiogenesis than evolution per se entails, since chemicals had to get to the point at which they could replicate, or at least to partly replicate.
Evolution needn't necessarily deal with abiogenesis at all, either, in order to be a highly successful theory. Darwin certainly suggested that God might have started life in the first place, the only(!) drawback to that being that there is absolutely no evidence for such a claim.
Under what we know at present, though, evolution is understood as having almost certainly been shaped in part by abiogenesis, so that even the pre-replication phase of abiogenesis is not fully divorced from evolution. Yet one can't deny that until sustained replication of the molecules that gave rise to later life arose, the story of abiogenesis has little or nothing to do with evolution as we know it. Nor do we really understand how molecules got to the point at which sustained replication became possible (work continues, naturally).— Glen Davidson - I guess "nudging chemicals" to "undergo evolution" is a form of ID, but it doesn't verify ID as the force behind nature. Logically, such a conclusion is fallacious.— jxxphilly
- No conclusion intended. Just a "scientific" observation. — Jack29
- After reading your comment again I realize I failed to congratulate you for making a good guess. Now I am wondering if there is more than one "form" of ID. — Jack29
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- Why was the "X" chemical group/structure left out of the article? Someone once thought they found arsenic for phosphorus substitution. You say that the researchers wear gloves to protect the fragile molecules of DNA and RNA. So how is it that intact and identifiable DNA is found in dino bones and other fossil bones (50 million years old or more as per evolution)? Answer: Because dinosaurs are not all that antient. Not only that, but C-14 is found in fossils (and coal, natural gas and diamond). This is another big problem for evolutionists. Check www.kgov.com/dinosaur-soft-tissue.— Ted Siek
- Although the article says: "There may be no moment when the first life emerged, but instead an evolutionary process by which chemicals that most of us would consider non-life gradually gave rise to living cells through natural selection."
... the Law of Biogenesis(1)tells us: "Life does not come from non-life."
The Law of Biogenesis is in accord with what the Bible has long told us:
that it is God who gives life to everything.(2)
References:
(1.) Law of Biogenesis
What Does Cutting-Edge Science Teach about Origins?
http://kolbecenter.org/images/kolbe/pdfs/what_church_teaches.pdf
(2.) Bible: Nehemiah 9:6 (NIV1984)
"You alone are the LORD. You made the heavens, even the highest heavens, and all their
starry host, the earth and all that is on it, the seas and all that is in them.
You give life to everything,
and the multitudes of heaven worship you."
http://www.biblegateway.com/passage/?search=Nehemiah9:6&version=NIV1984
— JosephU
In pursuit of her stories, writer Faye Flam has weathered storms in Greenland, gotten frost nip at the South Pole, and floated weightless aboard NASA’s zero-g plane. She has a degree in geophysics from the California Institute of Technology and started her writing career with the Economist. She later took on the particle physics and cosmology beat at Science Magazine before coming to the Inquirer in 1995. Her previous science column, “Carnal Knowledge,” ran from 2005 to 2008. Her new column and blog, Planet of the Apes, explores the topic of evolution and runs here and in the Inquirer’s health section each Monday. Email Faye at fflam@phillynews.com.
Reach Planet of the at fflam@phillynews.com.
