A study published in Nature Chemistry in May 2025 by Dr. James Attwater and Dr. Philipp Holliger at the MRC Laboratory of Molecular Biology, along with co-authors at UCL Chemistry, demonstrates exponential RNA replication using a polymerase ribozyme. By utilizing a trinucleotide-freeze-thaw mechanism, researchers bypassed the “strand separation problem,” offering a plausible chemical pathway for how self-replicating molecules might have functioned on the early Earth.
How did researchers overcome the “strand separation problem”?
The primary obstacle in the RNA world hypothesis is that RNA strands often bind too tightly to their complementary partners, creating a stable double helix that prevents further replication. According to the study, the team solved this by using trinucleotides—building blocks consisting of three RNA letters—rather than standard single-letter nucleotides. In a simulated geothermal environment, the researchers used alternating pH levels and freeze-thaw cycles. As the solution froze, the trinucleotides concentrated in liquid veins between ice crystals, coating the separated RNA strands and preventing them from zipping back into a double helix. This allowed for continuous, exponential replication.
The researchers specifically ruled out evaporation as a way to concentrate RNA. Because RNA degrades at the high temperatures required for evaporation, it would not have been a viable mechanism for early life.
Why is this result different from previous RNA studies?
Recent years have seen significant progress in prebiotic chemistry, but this work addresses a distinct bottleneck. In 2024, Gerald Joyce’s group at the Salk Institute focused on the “fidelity problem,” demonstrating an RNA polymerase ribozyme capable of higher accuracy. Separately, in early 2026, Holliger’s own laboratory developed a ribozyme called QT45 that could synthesize both itself and a partner strand. Unlike these studies, the May 2025 paper focuses on the physical cycle of replication. It provides a chemistry-based solution to the strand separation bottleneck that requires no protein machinery, marking a shift from theoretical models to a repeatable laboratory cycle.
What are the limits of the RNA world hypothesis?
While this finding is a meaningful step, the authors acknowledge it is not a complete account of the origin of life. According to Dr. James Attwater, LUCA—the Last Universal Common Ancestor—was a complex entity with a vast evolutionary history that remains hidden. Furthermore, the trinucleotides used in the experiment do not exist in modern biology. The current scientific consensus, supported by ongoing work from groups led by Dr. John Sutherland and Professor Matthew Powner at UCL and the MRC, suggests that life likely emerged from a combination of RNA, lipids, peptides, and metabolic chemistry rather than RNA alone.
Pro Tip: Tracking the Evolution of Primordial Codons
Keep an eye on whether other laboratories can replicate the team’s observation that random RNA sequences drifted toward hypothesized primordial codons. If this structural bias holds, it would suggest the genetic code was shaped by the physics of replication chemistry itself, rather than purely through selection.
Frequently Asked Questions
- Does this prove how life began? No. It demonstrates a plausible mechanism for RNA replication in a prebiotic environment, but it is not a final explanation for the origin of life.
- Can this process happen in saltwater? No. The study notes that salt disrupts the freezing process, preventing the necessary concentration of trinucleotides.
- What is the next challenge? Researchers must determine if this mechanism can sustain longer RNA sequences and eventually support the self-replication of a ribozyme under these specific conditions.
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