A DNA helix
DNA & RNA genetic information to be stored and propagated through the generations. Now researchers have created new molecules called XNAs by replacing the sugar molecules on the DNA or RNA phosphate backbone with an analog. From Science News:
The researchers, led by Philipp Holliger of the MRC Laboratory of Molecular Biology in Cambridge, England, did make completely new genetic molecules. In the backbone of every DNA molecule there are repeating units of deoxyribose sugar, in the RNA backbone it’s ribose sugar. Instead of those sugars, the various XNAs have different molecules in their backbones: a five-carbon sugar called arabinose in ANA, the ringed structure anhydrohexitol in HNA, and threose, a four-carbon sugar in TNA. The scientists also created XNA molecules called FANA (2´-fluoroarabinose), CeNA (cyclohexene) and LNA (“locked” ribose analog).
In a second bioengineering feat, the researchers created special enzymes for the XNAs so that they could evolve. This requires enzymes that can “read” the order of molecular components in a strand of XNA and use that information to build a complementary strand of DNA. Working with an enzyme from a sulfur-loving microbe, the team selected for versions that could “read” each of the XNAs. The researchers also made enzymes that could do the reverse: read DNA and use that information to build XNA.
Because the XNAs can’t copy themselves without help from DNA, it’s not truly synthetic life, says Joyce. But the molecules do undergo good old-fashioned evolution. With HNA, for example, the researchers created a random population of HNA molecules, then exposed them to a bunch of target molecules (such as proteins or RNA) for the HNA to attach to. Most of the HNAs didn’t do diddly-squat, but a fraction were slightly better at connecting to the target molecules.