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Short Sharp Science: A New Scientist blog

Biologists create self-replicating RNA molecule

Michael Marshall, environment reporter




RNA is structurally similar to DNA and can also be used to store genetic information. Some RNA molecules can act as enzymes, driving important chemical reactions in cells, but an RNA enzyme that can reliably copy other RNA segments, let alone self-replicate, has proved elusive.

Until now, the only known RNA-copying RNA was a molecule called R18, which can only copy RNA segments up to 14 "letters" long, and only works on certain sequences. It's like a word processor that can copy-and-paste "turnip" but not "swede".

Holliger, who is based at the MRC Laboratory of Molecular Biology in Cambridge, UK, has now set out to improve R18. He made a vast library of thousands of different versions of the molecule and screened them to see which ones made more copies. After several rounds of copying variants and looking for new improvements, he found several useful tweaks, which he incorporated into his final patchwork enzyme, tC19Z.

tC19Z can reliably copy RNA sequences up to 95 letters long, a near-sevenfold increase on R18. Its performance varies depending on the sequence it's copying, but it is much less picky than R18. Holliger compares R18 to a sports car that works only on a smooth, flat road. "We have fitted a four-wheel drive, so it can go off-road a bit," he says.

Crucially, tC19Z can copy pieces of RNA that are almost half as long (48 per cent) as itself. If an RNA enzyme is to copy itself, it has to be able to copy sequences as long as itself, and tC19Z is closing in on that goal.

In a neat twist, Holliger's team also showed that tC19Z can make copies of another RNA enzyme, which then worked correctly. That suggests that, once the first self-replicating RNA had appeared, it would have been able to surround itself with additional molecular equipment, kick-starting the evolution of more complex life.

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Yes, much more like it.
Does the enzyme have to be a single strand to function - or might it still work cut into two or more parts? - if so - job done.


Is this article accurately titled 'Biologists create self-replicating RNA molecule' when in the penultimate paragraph I'm told it can only replicate half its length. Isn't that a bit like saying 'Mechanic builds self assembling car in Austraila' and then finding only half of is being built when I get there? I could have saved my ticket money for when it could fully build? I was really annoyed, why did i have to almost finish the article before I knew the title was wrong? How can I trust your titles ever again New Scientist?


Headline is wrong: if biologists had created a self-replicating RNA, it could replicate 100% of itself, not 50%.


How many scientific minds did it take to create this? It's pretty funny to think that many scientists don't believe that it took a mind to create the true first enzymes!


Using evolutionary algorithms, to artificially 'evolve' RNA molecules, to discover the beginnings of evolution... cool!!

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