Scientists Nagoya University in Japan have shown that the precursors of living organisms on Earth could be molecules similar to DNA, but not RNA. This is reported in an article published in the journal Nature Communications. The scientific work is summarized in a press release on MedicalXpress.
The researchers believe there was a pre-RNA world based on xenonucleic acids (XNA) before the first living cell existed. Unlike RNA chains, the replication and assembly of XNA requires no enzymes. XNA chains are stable enough to carry genetic information. They are also able to bind to proteins and have enzymatic functions similar to ribozymes (what scientists call ribonucleic acids that can catalyze biochemical reactions).
Scientists synthesized fragments of the aliphatic (non-cyclic) nucleic acid L-threoninol (L-aTNA), which is thought to have existed before RNA. They also made a longer chain of L-aTNA that was complementary to the original fragment sequence, just as two DNA chains complementary to each other create a double helix.
In vitro, under controlled conditions, the shorter L-aTNA fragments came together and bound to each other on the longer L-threoninol chain. This occurred in the presence of a compound called N-cyanoimidazole and a metal ion such as manganese, both of which were likely present on early Earth.
The L-aTNA fragments could also bind to DNA and RNA. This suggests that the genetic code could be transferred from DNA and RNA to L-aTNA and back again.
According to the scientists, the results of the study will help future developments in the creation of artificial life and highly functional biotechnological tools consisting of acyclic XNA.