Whoever said DNA was an exclusive?

If you thought that DNA or its sister molecule, RNA, were the only means of storing genetic information-think again!   A team of researchers at Cambridge University have successfully created synthetic alternatives called xeno-nucleic acids (XNAs) which can not only store genetic information- but are almost as capable of evolving.

Picture it: a spiralling ladder-with each step a sugar bound to a molecule in the middle called a base (one to each sugar) and you have envisaged the very basic structure of DNA.   The base can be one of four different molecules, represented by the letters A, C, T and G.  RNA is similar but bears some important differences, being single as opposed to double stranded and having U instead of T as a base.  However, it was not so much the bases that the researchers were interested in -but the sugar element.  By replacing the sugar with other alternatives, they managed to produce six different XNAs.

To test whether or not XNAs were capable of evolving, the team presented various XNAs with a ‘survival challenge:’ they were to bind to one of two target molecules (a protein and a molecule RNA) –or be washed away. Those that stuck were replicated and given the same treatment again.  With each test, variations in the genetic code led to XNAs that were increasingly adept at binding the targets.  They displayed a capacity for change, such as we might see with DNA or RNA.

There is much to be done before it is possible to create the first XNA-based synthetic life form.  So far, the team have managed to replicate XNA by converting it back to DNA for use as a template, but have not yet found a way of doing so without using DNA as an intermediate.  Nonetheless, the implications are vast.

The sugars seen in RNA or DNA are both relatively complex, so it is quite possible that simpler alternatives like certain XNAs came first in the evolution of life on Earth, some scientists believe.  Crucially though, as Dr. Phillip Holliger of the UK Medical Research Council’s Molecular Biology Laboratory explains; the research shows that “heredity-information storage and propagation- and evolution…two hallmarks of life…can be reproduced and implemented in alternative polymers other than DNA and RNA.” If there is life beyond Earth, who knows what it might use instead!