Like DNA … But More EXTREME

Move over DNA: Six new molecules can carry genes

[…] A host of alternative nucleic acids have been made in labs over the years, but no one has made them work like DNA.  This problem has now been cracked. “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.

A key hurdle 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.  They started with enzymes that do this in DNA only. Over the years the team made incremental tweaks until they produced enzymes that could work on XNAs.

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.

This is the first time artificial molecules have been made to pass genes on to their descendants. Because the XNAs can do this, they are capable of evolution.

“The immediate question is whether these XNAs can be introduced into cells,” says Farren Isaacs of Yale University in New Haven, Connecticut. Once the XNAs were installed, they could replicate and evolve on their own. “That would be remarkable.”

To be clear, this isn’t an article about the discovery of new molecules that can carry information, but rather their development.  At this point, the “evolution” they’re talking about would be prompted by replication done at the prompting of scientists.  This would obviously change once these new XNAs are put into cells either in the place of – or alongside – their DNA.

I’m wondering if they’ll be creating simple viruses or viroids with the XNA as well.  Nothing harmful, of course, but as more of a proof of concept … even as a possible way to show how life can start and maintain itself through an alternate means of information transfer.

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2 Responses to Like DNA … But More EXTREME

  1. Richard says:

    I wonder whether they can answer why these molecules don’t occur in nature? I mean, DNA and RNA seem to have won out in a big way. Did the first DNA-using things just get lucky and take over the world by exponential division, or is there e.g. some energetic penalty for these XNA molecules that make them less competitive?

    • I suppose there was some likely advantage to the way DNA / RNA replicated back on early pre-life earth that made them so successful relative to other concurrent processes. The study showed that information could be stored using these enzymes, but there wasn’t much information about the relative efficiency among the different kinds they developed. It’s entirely possible they’d fail miserably by natural selection.

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