Each cell in a living organism has an instruction manual known as the genome. These instructions are spelled out using letters, called bases, that pair with one another to form long double-stranded molecules of helical DNA. Life as we know it uses 4 bases called A, C, T, and G. Recently, scientists expanded this alphabet to include 8 bases – 4 natural and 4 artificial. They dubbed the new code hachimoji DNA (‘hachi’ for eight, and ‘moji’ for letter).
To create the new artificial bases, scientists first studied the properties of the four naturally occurring bases. Two properties of the artificial bases are particularly important. First, the artificial bases have to be similar in size to each other and to the natural bases. Second, the new bases have to be able to form hydrogen bonds with one another in order to pair and fit into the DNA helices. Using molecular modeling predictions that required optimizing over 60 different properties, scientists came up with several artificial structures.
After confirming that the hachimoji DNA formed structures similar to natural DNA, scientists asked whether the hachimoji instructions could be recognized and transcribed by enzymes (a necessary step when using DNA to create proteins). While the native enzyme was unable to do so, a mutated version of this enzyme could transcribe all the new hachimoji letters, as well as all the natural letters.
This research raises a host of deep questions about life in our universe. First, it suggests that life does not have to be built with only 4 bases. There might be undiscovered life-forms in the cosmos that use an expanded alphabet. Expanding the genetic code from 4 to 8 bases exponentially increases the amount of combinatorial information that can a single DNA molecule can contain (similar to progressing from 8-bit to 16-bit computers). For technologists, this development is particularly exciting as it opens new possibilities for information storage. The computing information that we currently store using binary systems (1s and 0s) could one day be stored using synthetic DNA, in a manner similar to cells in our body.
Popular news article: https://www.nytimes.com/2019/02/21/science/dna-hachimoji-genetic-alphabet.html
Original scientific article: http://science.sciencemag.org/content/363/6429/884
Managing Correspondent: Radhika Agarwal