A team of researchers has taken us closer to understanding how RNA and DNA components came together to form the chemicals that existed on Earth before any forms of life were present. Using simple laboratory reactions in water under standard conditions, the team was able to create candidates for the missing links in the process that led to the formation of life.
Scientists have long believed that before life forms used DNA to store genetic information, they used RNA in a broad manner. Furthermore, this RNA might have even been preceded by proto-RNA, which possessed different but similar nucleotides.
"Early Earth was a messy laboratory where probably many molecules like those needed for life were produced," said Nicholas Hud, a professor at the Georgia Institute of Technology who led the study. "Some survived and prospered, while others eventually vanished. That goes for the ancestors of RNA, too."
The team created proto-nucleotides using two molecules of barbituric acid and melamine and found that the results were extremely similar to two of RNA's nucelotides, prompting the researchers to hypothesize that these two ingredients - which would have been in high supply on a prebiotic Earth - might have been ancestors of RNA nucleotides.
"They would have been well suited for primitive information coding," Hud said.
Despite the promise of the findings, it's too early to jump to this conclusion yet.
"To claim ancestry, we would have to show a mechanism by which these nucleotides we made in the lab could turn into the existing nucleotides in RNA," said Ram Krishnamurthy, co-author of the study and a researcher from Scripps Research Institute in La Jolla, Calif. "It's a complex path that we'd have to at least design on paper, and we're not there."
"There are umpteen possibilities of how that mechanism could have happened," he continued. "Barbituric acid and melamine may have been place holders that dropped out and allowed adenine and uracil to come together with ribose."
The team hopes that its findings will help scientists advance their understanding of chemical evolution and the formation of the first life forms on Earth.
"If you want to look at what brought about these properties of life you have to go back and consider all the other molecules that would have been present and see how they would have facilitated the molecules that are present in life today," Krishnamurthy said.
The findings were published in the April 25 issue of Nature Communications.