An illustration of the newly synthesized DNA variant. The four ingredients of regular DNA are shown in green, red, blue, and yellow, and the new ingredients are shown in cyan, pink, purple, and orange. Indiana University School of Medicine
As far as we know, all life on Earth is based on DNA — and DNA is used for everything from health applications to data storage to solving crimes. But now a new study funded by NASA has made a dramatic breakthrough in understanding molecular systems by synthesizing a molecular system which could be an alternative to DNA.
The research was funded by a space agency because it is one way that we could search for life on other planets. Most approaches to the search for extraterrestrial life focus on what we understand as the essentials for living organisms, such as the presence of liquid water and elements like oxygen and nitrogen. But some people argue that this approach is too anthropomorphic — that we assume that life elsewhere would be like life as we know it, and that could be a mistake. The new study posits that life could theoretically exist in a way which is completely different from anything here on Earth.
“Life detection is an increasingly important goal of NASA’s planetary science missions, and this new work will help us to develop effective instruments and experiments that will expand the scope of what we look for,” Lori Glaze, acting director of NASA’s Planetary Science Division, said in a statement.
The researchers, a team lead by Steven Benner at the Foundation for Applied Molecular Evolution in Alachua, Florida, managed to fabricate a new informational molecular system which is similar to DNA but has one key difference: Where DNA has four nucleotides, the new molecular system has eight. Nucleotides are molecules which add together to build DNA, and there are four of them in every kind of life discovered so far — adenine, thymine, cytosine, and guanine (or ATCG, as you’ll see in DNA diagrams.) These four nucleotides bind together in pairs of two to store biological information and are held together to form the double helix structure of DNA.
The new synthetic DNA includes the same four nucleotides plus four others which have similar informational structures, bound together to in a helix which can store information just like regular DNA. This demonstrates how life could possibly exist with a DNA structure different from what we know. The new DNA is called “hachimoji” DNA (from the Japanese words meaning eight and letter.)
Benner argues that this finding can further our understanding of what life can look like beyond our planet: “By carefully analyzing the roles of shape, size and structure in hachimoji DNA, this work expands our understanding of the types of molecules that might store information in extraterrestrial life on alien worlds,” he said.
The findings are published in the journal Science.
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