In a spectacular discovery, Harvard scientists announced that they have stumbled upon a potential “new ingredient” for life — one that is not found in modern RNA and which could rewrite the story of how life appeared on Earth.
According to their finding, there may have been more than just one path for life to evolve in our planet’s distant past. One was the formation of RNA — the active messenger of DNA, that carries its instructions — from the four chemical compounds that are known today. But researchers have uncovered that another path might also have been possible by tweaking the recipe of RNA.
“Life needs three major pieces: protein, DNA, and RNA,” underlines a news release from Harvard University. Short for ribonucleic acid, RNA is a fundamental compound of all living cells.
“A complex but versatile molecule, RNA stores and transmits genetic information and helps synthesize proteins, making it a capable candidate for the backbone of the first cells.”
RNA molecules are made up of four basic chemical compounds known as nucleotides: adenine, guanine, cytosine, and uracil (or A, G, C, and U). For a long time, scientists have been trying to figure out which ingredients that existed on early Earth reacted to form these four chemical compounds. While previous research made important progress in finding precursors to C and U, the quest for the roots of A and G arrived at a standstill.
In an attempt to shine the light on the primordial ingredients that led to the creation of the building blocks of life, a research team led by Harvard graduate student Seohyun Chris Kim has tried to replicate A and G in the lab. The experiment didn’t pan out as they had hoped, leading to an array of “undesired side products.”
It was then that the researchers had the idea to replace G with a surrogate — inosine, or I. The team even managed to craft specific versions of A and I “from materials available on primeval Earth.”
The task at hand was to find out whether RNA molecules built following the new recipe were able to store and copy genetic information in order to successfully replicate.
“If it replicates too slowly, it falls apart before completing the process. If it makes too many errors, it cannot serve as a faithful tool for propagation and evolution,” explains the university.
Alas, the new versions of A and I proved unsuited for the job. However, the experiment revealed that the original form of inosine was much more efficient, enabling RNA to replicate fast and with few errors, reports Phys.org.
— Phys.org (@physorg_com) December 3, 2018
In a new study published today in the journal PNAS, the scientists advocate that “inosine could have served as a surrogate for guanosine in the early emergence of life.”
“Our study suggests that the earliest forms of life (with A, U, C, and I) may have arisen from a different set of nucleobases than those found in modern life (A, U, C, and G),” Kim said in a statement.
This revelation could have important implications not only in our understanding of what ignited the spark of life — the chemical and environmental conditions necessary for life to appear, also known as prebiotic precursors, as previously reported by the Inquisitr — but also in our search for life on other planets.
Any new development that brings us closer to uncovering the ingredients of life might help astronomers pinpoint the planets that host those ingredients, thereby finding new worlds where life could have a chance to be born and evolve.