Deoxyribonucleic acid, more commonly known as DNA is the building block for all living things on Earth. It usually consists of four nucleic acid bases Guanine (G), Adenine (A), Cytosine (C), and Thymine (T) that form a consistent, if simple pairing: Guanine goes with Cytosine and Adenine goes with Thymine to form DNA’s characteristic stable helix. They carry all of the instructions of the “genetic code” in this helix; allowing everything from simple bacterium to complex organisms like human beings to develop and function normally.
Since the late 1990’s, scientists have been searching for synthetic molecules that can pair up to make the DNA helix, unzip just as easily, and transcribe onto the associated RNA molecules to create new DNA strands. The first step was recombinant DNA, which is made by combining DNA from two or more different biological sources. Truly artificial DNA is made from molecules that do not naturally occur in nature. For example, researchers created XNA, or DNA molecules with artificial sugar backbones that could be manipulated and subsequently evolve. Artificial DNA that incorporates synthetic bases has been successfully replicated in a test tube since 2008. Yet neither of these processes had worked in a living cell, until now. As of May 2014, a team of scientists at the Scripps Research Institute, also known as TSRI, in California have successfully made a live bacteria with a working strand of artificial DNA.
This modified bacteria is not the same as creating artificial life per se, but rather an achievement that demonstrates unexplored potential of the molecule itself. The term “artificial” DNA is also a bit of a misnomer, as the new DNA strand is not entirely synthetic, but rather a mix of the usual DNA molecules, A, C, T and G, and a third pair of artificial molecules not found in nature, known as d5SICS and dNaM. The TSRI scientists incorporated these molecules into a circular strand of DNA known as a plasmid and then inserted that plasmid into the DNA of an Escherichia coli bacteria.
The result was a functional bacteria with hybrid DNA that could duplicate both the organic and the artificial bases with the same speed and accuracy as the fully organic version. However, these synthetic bases require a special “transporter” protein in order to be moved into cells as well as a steady supply of the synthetic bases themselves in order to replicate the artificial DNA strand. When either are missing, d5SICs and DNaM are eliminated from the genome with each further replication and the cell eventually reverts back to the natural formula.
These artificial bases provide the potential for the creation of new, specially designed proteins that don’t otherwise exist in nature. In order to make a protein, a DNA sequence is divided into sets of three base pairs to become the “reading frame.” The frame dictates which amino acids are brought in to make up the protein sequence. Proteins made from artificial DNA template could be used to design new therapies, diagnostic tests and reaction reagents. The rapid replication cycles of bacteria means that these unique proteins could be churned out at a rate that is both cheap and effective. Altogether, the rising advancements made with artificial DNA only highlights the possibilities that this small but important molecule offers.