Advancing Toward Synthetic Life: XNA


By Cory Bickel

XNADNA and RNA are the molecules that make up and carry out the instructions of the genetic code of every organism on Earth. But a new twist on these molecules has opened up possibilities of synthetic life forms with non-traditional genetic material. XNAs, or xeno-nucleic acids, are slightly altered forms of DNA. DNA has a backbone of sugar molecules strung together in long chains. By changing these sugar molecules from the usual form, six different XNAs were made with different sugar backbones. Attached to the sugar backbone in DNA and XNA are the bases A, T, C or G, and the order of these bases spells out the genetic code. Because these bases are unchanged in XNA, it has the same ability as DNA to store genetic information.

XNA Can Be Inerited

Scientists also created enzymes that could make a DNA copy of XNA with fairly high accuracy, as well as enzymes that were capable of reading a DNA sequence and making XNA. The ability of XNA to be copied in this way means that it can be considered inheritable, just like DNA.

XNA Can Evolve

An experiment that mimicked Darwin’s process of natural selection showed that XNAs are capable of evolving. After many rounds of amplification, mutation and selection of a pool of XNAs, sequences were found that had evolved to bind specific RNA or protein targets.

The abilities of XNAs to be inherited and evolve mean that they possess the same properties that make DNA a functional genetic material. Although there is a lot more work to be done, XNA could, in theory, be used to create completely synthetic life forms that could reproduce and adapt to new environments.

Classroom Discussion

  • XNA show that non-traditional molecules could be capable of carrying genetic information and supporting life; what does this mean regarding the search for life on other planets?
  • XNA is a potential source of new drugs and therapies because of its ability to bind molecules very specifically; why does its synthetic nature give it an advantage over DNA or RNA for these applications?