London: Scientists are closer to demonstrating that DNA can form spontaneously from chemicals thought to be present on the primordial Earth suggesting that DNA could have predated the birth of life itself.
Deoxyribonucleic acid (DNA) is essential to almost all life on Earth, yet most biologists think that life began with Ribonucleic acid (RNA). Just like DNA, it stores genetic information.
Prebiotic chemists have so far largely ignored DNA, because its complexity suggests it cannot possibly form spontaneously, the New Scientist reported.
Conventional wisdom is that RNA-based life eventually switched to DNA because DNA is better at storing information. In other words, RNA organisms made the first DNA.
“The story makes more sense if DNA nucleotides were naturally present in the environment. Organisms could have taken up and used them, later developing the tools to make their own DNA once it became clear how advantageous the molecule was— and once natural supplies began to run low,” Christopher Switzer of the University of California, Riverside said.
RNA can also fold into complex shapes that can clamp onto other molecules and speed up chemical reactions, just like a protein, and it is structurally simpler than DNA, so might be easier to make.
In 2009 researchers finally managed to generate RNA using chemicals that probably existed on the early Earth.
Matthew Powner, now at University College London, and his colleagues synthesised two of the four nucleotides that make up RNA. Their achievement suggested that RNA may have formed spontaneously—powerful support for the idea that life began in an “RNA world”.
In his latest work, Powner is trying to make DNA nucleotides through similar methods to those he used to make RNA nucleotides in 2009.
Nucleotides consist of a sugar attached to a phosphate and a nitrogen-containing base molecule – these bases are the familiar letters of the genetic code.
DNA nucleotides, which link together to form DNA, are harder to make than RNA nucleotides, because DNA uses a different sugar that is tougher to work with.
Starting with a mix of chemicals, many of them thought to have been present on the early Earth, Powner has now created a sugar like that in DNA, linked to a molecule called AICA, which is similar to a base.
“A DNA nucleotide is just a few years away. It’s practically a fait accompli at this point,” Switzer said.
PTI
