December 27, 2013 - One of the biggest questions in science is how life
arose from the chemical soup that existed on early Earth. One theory is that RNA, a close relative of DNA, was the first genetic molecule to arise around 4 billion years ago, but in a primitive form that later evolved into the RNA
molecules that we have in life today. New research shows one way this chain of events might have started.
Today, genetic information is stored in DNA. RNA
is created from DNA
to put that information into action. RNA
can direct the creation of proteins and perform other essential functions of life that DNA
can't do. RNA's versatility is one reason that scientists think this polymer came first, with DNA
evolving later as a better way to store genetic information for the long haul. But like DNA, RNA
also could be a product of evolution, scientists theorize.
Chemists at the Georgia Institute of Technology
have shown how molecules that may have been present on early Earth can self-assemble into structures that could represent a starting point of RNA. The spontaneous formation of RNA
building blocks is seen as a crucial step in the origin of life, but one that scientists have struggled with for decades.
"In our study, we demonstrate a reaction that we see as important for the formation of the earliest RNA-like molecules," said Nicholas Hud, professor of Chemistry
and Biochemistry at Georgia Tech, where he's also the director of the Center for Chemical Evolution.
The study was published Dec. 14 online in the Journal of the American Chemical Society. The research was funded by the National Science Foundation
and NASA. RNA
is perfect for the roles it plays in life today, Hud said, but chemically it's extraordinarily difficult to make. This suggests that RNA
evolved from simpler chemical couplings. As life became more chemically complex and enzymes were born, evolutionary pressures would have driven pre-RNA
into the more refined modern RNA. RNA
is made of three chemical components: the sugar ribose, the bases and phosphate. A ribose-base-phosphate unit links together with other ribose-base-phosphate units to form an RNA
polymer. Figuring out how the bond between the bases and ribose first formed has been a difficult problem to address in the origins of life field, Hud said.