My nephew shared a very thought-provoking news article. Recently, a group from The Scripps Research Institute published a paper in the journal Nature detailing an engineered bacterium that can use synthetic nucleotides. Basically, they put lab-made DNA into bacteria, and it worked.
Normally, there are 4 bases used to make DNA. Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Normally, they pair up to make the double helix. An Adenine on strand of DNA will pair up with a Thymine on the other strand. Likewise, a Cytosine on one strand will pair with a Guanine on the other. The group added two extra, man-made bases to the DNA double helix, which they abbreviated X and Y. The new nucleotides were replicated with the normal DNA, and weren’t removed by the cell’s normal DNA repair machinery.
Besides the obvious difficulties of making nucleotides that could be inserted into DNA, this study provided a lot for me to think about. There are a lot of implications outside of the “We can do this!” excitement. For example, in the biology class I teach, we are currently studying evolution. One of our main concepts is looking at the relationships between organisms, and the biggest relationship all living things have is the genetic code. It’s amazing, really. Every living thing on this planet uses the exact same code to build and pass on information. The same four letters of DNA have all the information every single little cell needs to live and to replicate and to grow. But this study demonstrates that those four letters, A, C, G, and T, are not the only possible ways information could potentially be passed on. Because we all have the same ancestry, though, we use the same code.
The study also demonstrates what we, as humans, don’t know (which is, of course, a lot more than we’d like to admit). Looking for life in outer space is an exciting area of research. But all we know is what life on earth looks like. How can we recognize extra-terrestrial life? It could be very different from what we know. It would almost certainly not use the exact 4 nucleotides life on earth uses. It might use a completely different method of storing and passing on information that what we use. The “life” that we know and are looking for might not exist outside earth. If we do come across some alien cells, they could easily be dismissed as inorganic material, simply because they don’t chemically resemble what we know as life.
There are, of course, other massive implications from the creation of this semi-synthetic life. These were just the first thoughts that popped into my head. What do you think about adding man-made DNA to bacteria?