Billions of years ago, four kinds of molecules that spun and jumped on our planet, like the sudden will, gracefully formed the DNA double helix in a way we still can’t imagine, for the life on our planet. A genetic code is provided. These four molecules are adenine, guanine, cytosine, and thymine. We usually use the four letters A, G, C, and T to represent these four natural bases. Under normal circumstances, when the two DNA strands wound together to form a double helix, each strand will base on the key pair to each other: A for T, C for G .
Nowadays, a recent study published in the journal Science shows that the composition of this life has changed from four to eight ! Scientists have succeeded in creating synthetic bases that can also store and transcribe genetic information. In theory, these extended synthetic bases can also be used to support life.
This is a milestone. Because it shows from the side that there are no special magical powers for the four natural bases that are closely related to the evolution of life on Earth.
In fact, scientists have long thought about whether these four bases can form the basis of life. They try to add more bases to the genetic code. As early as the 1980s, chemist Steve Benner , who led the research, first created “unnatural” bases. Since then, many different research groups have also carried out such research.
So what is special about the new research? It is the first systematic proof that unnatural bases recognize and bind to each other like natural bases and form a self-sustaining stable double helix. The researchers created these synthetic bases by adjusting the molecular structure of common bases.
We know that the base pairing of DNA is due to the formation of hydrogen bonds between the bases: the hydrogen atoms of each base are attracted to the nitrogen or oxygen atoms in their corresponding “sports”. By adjusting these molecules, researchers have found several new bases, wherein a pair designated B and S , on the other named P and the Z .
The researchers combined the four additional synthetic bases with four standard natural bases, calling the 8-base system ” Hachimoji “, meaning “eight-character” (Hachi means eight in Japanese, Moji is the text) . The four synthetic bases are similar in shape to the four natural bases except that there are some differences in the binding pattern. They conducted a series of experiments and finally proved that the synthetic DNA sequence has the same characteristics as the natural DNA necessary for life.
We can understand the properties of these synthetic bases in three ways.
First, as an information storage system, DNA must follow predictable rules. Therefore, they must first prove that synthetic bases are similar to ordinary bases and can be paired stably and reliably. They made hundreds of synthetic DNA molecules and found that these synthetic bases can be paired with their respective “camps” as expected.
Next, they found that the stable double helix structure of the DNA was maintained regardless of the order in which the synthetic bases were arranged in the DNA. They created three different sequences of synthetic DNA, which were examined by X-ray diffraction and found to maintain a constant structure during crystallization.
This is very important because life evolves in DNA changes, and if evolution is to be carried out, the DNA sequence must be able to change without destroying the overall structure. This is a major leap in this study, and other methods of extending bases are unable to maintain overall structural stability. In those methods, the researchers used not the chemical paired with hydrogen bonds, but the hydrophobic molecules to make bases. Such bases can only be inserted between natural bases at intervals. If they are to be arranged in a row, the overall structure of the DNA molecules will collapse.
Finally, the team demonstrated that the synthesized DNA can be faithfully transcribed into RNA. This is also a crucial point. Because converting DNA into RNA is a critical step in turning genetic information into protein, and protein is the backbone of our lives.
The breakthrough in this research is conceptual, and it clearly shows that life can be supported by four DNA bases different from what we know. This is a great reference for us to search for signs of life elsewhere in the universe.
In addition to being used to find life in the universe, there are many more practical applications for this DNA strand with extra bases. By increasing the number of base species to eight, the diversity of DNA sequences will be greatly increased, and the genetic information that can be stored will also increase greatly. In addition to information storage, DNA containing 8 bases can be more specifically combined with a specific target. For example, in a previous study, Benner’s team found that DNA strands containing Z and P bind better to cancer cells than just the standard four-base DNA strand.
This is the first time to display DNA with 8 different base letters, which is amazing , this is an exciting starting point. But at the same time, there may be a long way to go to achieve a true “eight-letter” synthetic gene system. For example, in practical applications, researchers need to improve the accuracy and efficiency of RNA replication and transcription. Benner’s research team is still developing more new base pairs, which opens up the possibility of creating DNA with more base letters.