All the information that makes living organisms what they are is encoded in DNA. All the variation that we observe is encoded in these molecules, each written using an alphabet of just four letters. Researchers have now discovered that it is possible to use four additional synthetic letters.
The natural “letters” are nucleotides, compounds that interact in a predetermined way to construct the molecules of DNA. The molecules are adenine, cytosine, guanine, and thymine, and the way they are ordered provide organisms with the instructions to build proteins.
As reported in Science, researchers have created what they are calling "hachimoji DNA", with the name coming from the Japanese words for eight (hachi) and letter (moji). The synthetic DNA meets the structural requirement to support Darwinian evolution. Analysis actually shows that the 8-letter version packs more information in the same length of DNA and can be transcribed into RNA just like regular DNA.
The work is supported by NASA and for good reason. Such a discovery tells us that terran DNA is not the only way that the universe can encode life. There might be organisms out there for which hachimoji DNA is the standard rather than a curious discovery.
“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,” team leader Steven Benner, Foundation for Applied Molecular Evolution in Alachua, said in a statement.
The detection of life beyond Earth is an important goal. A constant question that scientists ask themselves is “will we be able to recognize alien life as life?” This work and similar endeavors provide us with clues on what alien life might look like.
“Incorporating a broader understanding of what is possible in our instrument design and mission concepts will result in a more inclusive and, therefore, more effective search for life beyond Earth,” added Mary Voytek, senior scientist for Astrobiology at NASA Headquarters.
The breakthrough discovery of DNA with eight nucleotides, suitable for storing and transmitting information, shows that life not only finds a way, it finds multiple ones.