Six kinds of synthetic DNA created

Six new kinds of artificial genetic material have been created by scientists. These XNAs, or xeno-nucleic acids, have similar life-building properties to naturally-occurring DNA.

The work done by researchers at the MRC Laboratory of Molecular Biology in Cambridge, UK, is the latest important contribution to the field of synthetic biology where the building blocks of life are built in the lab almost from scratch.

Dr Philipp Holliger, a senior author on the study, published in the journal Science, said that the research showed 'that both heredity - information storage and propagation - and evolution, which are really two hallmarks of life, can be reproduced and implemented in alternative polymers other than DNA and RNA'.

XNA is comprised of the same four nucleic acids that DNA uses for coding proteins, but the structural frame has been made using different sugars. The research showed that the XNAs could form a double helix with the DNA and were more stable than the naturally-occurring genetic material.

The team made a polymerase, a kind of enzyme, which could convert DNA into XNA and XNA back into DNA, this demonstrates heredity. This involved mutating and screening natural DNA polymerases until one could read the XNA code. Selective evolution was demonstrated by an increase in the rate of XNA binding to the correct target over eight generational cycles.

Professor Eric Kool of Stanford University, California, who was not involved in the study, told The Scientist that 'chemists had been working for 20 years to find new backbones for DNA and the feeling always was that it would be interesting and quite possible that some of them might be replicated one day. The hard part was finding the enzymes that could do it'.

In an article accompanying the paper, Professor Gerald Joyce of the Scripps Research Institute in the USA said that the research 'heralds the era of synthetic genetics, with implications for exobiology [life elsewhere in the Universe], biotechnology, and understanding of life itself'.

The critical implication for exobiology is that any number of structures may be used as alternatives for DNA and RNA. As Dr Holliger told Science, 'there is no overwhelming functional imperative for genetic systems or biology to be based on these two nucleic acids'.

But the study also opens avenues for biotechnology and drug design. Gene therapy uses natural components that can be broken down by enzymes before the genes can be delivered within the cell. XNA does not degrade as readily as DNA and RNA. As Professor Joyce told The Scientist: 'These things are bullet-proof'.

In his article accompanying the paper, Professor Joyce pointed out that as the researchers had used a DNA intermediary to enable the XNA to replicate, their work did not represent a full synthetic genetics platform.