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Concept
Acide xénonucléique
Résumé
Xeno nucleic acids (XNA) are synthetic nucleic acid analogues that have a different sugar backbone than the natural nucleic acids DNA and RNA. As of 2011, at least six types of synthetic sugars have been shown to form nucleic acid backbones that can store and retrieve genetic information. Research is now being done to create synthetic polymerases to transform XNA. The study of its production and application has created a field known as xenobiology.
Although the genetic information is still stored in the four canonical base pairs (unlike other nucleic acid analogues), natural DNA polymerases cannot read and duplicate this information. Thus the genetic information stored in XNA is "invisible" and therefore useless to natural DNA-based organisms.
The structure of DNA was discovered in 1953. Around the early 2000s, researchers created a number of exotic DNA-like structures, XNA. XNA is a synthetic polymer that can carry the same information as DNA, but with different molecular constituents. The "X" in XNA stands for "xeno," meaning stranger or alien, indicating the difference in the molecular structure as compared to DNA or RNA.
Not much was done with XNA until the development of special polymerase enzyme, capable of copying XNA from a DNA template as well as copying XNA back into DNA. Pinheiro et al. (2012), for example, has demonstrated such an XNA-capable polymerase that works on sequences of ~100bp in length. More recently, synthetic biologists Philipp Holliger and Alexander Taylor managed to create XNAzymes, the XNA equivalent of a ribozyme, enzymes made of RNA. This demonstrates that XNAs not only store hereditary information, but can also serve as enzymes, raising the possibility that life elsewhere could have begun with something other than RNA or DNA.
Strands of DNA and RNA are formed by stringing together long chains of molecules called nucleotides. A nucleotide is made up of three chemical components: a phosphate, a five-carbon sugar group (this can be either a deoxyribose sugar—which gives us the "D" in DNA—or a ribose sugar—the "R" in RNA), and one of five standard bases (adenine, guanine, cytosine, thymine or uracil).
Source officielle
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