Biologists at the MRC Laboratory of Molecular Biology in Cambridge, UK, have synthesized an RNA enzyme that functions like a self-replicator.

The RNA enzyme tC19Z can reliably copy RNA sequences up to 95 letters long. This is a near-sevenfold increase over the R18 molecule, the only other known RNA-copying molecule. R18 can only copy RNA segments up to 14 letters long, and only works on certain sequences.

The tC19Z enzyme 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 — tC19Z is almost there.

The biologists showed that tC19Z can also make copies of another RNA enzyme. This suggests that, once the first self-replicating RNA evolved, it would have been able to surround itself with additional molecular equipment to kick-start more complex life.