A strand of RNA just 45 nucleotides long can copy its own complementary sequence in frozen conditions that may resemble early Earth, according to a study published in Science in early 2026. The molecule, called QT45, is described by the study’s authors as the smallest RNA polymerase ribozyme to approach self-replication, and its performance in ice is reshaping how scientists think about the chemical origins of life.
“This is the first time we’ve seen a ribozyme this small carry out template-directed synthesis of its own complement,” said Katrina Tjhung, the paper’s lead author and a researcher at the MRC Laboratory of Molecular Biology in Cambridge, UK. “It suggests that the barrier to self-replication in RNA may be lower than we thought.”
The result does not mean researchers have created life in a test tube. QT45 still needs supplied building blocks and carefully controlled conditions to function. But the fact that such a tiny molecule can perform template-directed copying at all represents a significant step toward answering one of biology’s deepest questions: How did the first self-replicating molecules arise on a planet that had none?
A ribozyme small enough to be plausible
Previous RNA enzymes engineered to copy other RNA strands were typically hundreds of nucleotides long, far too complex to have appeared spontaneously in a prebiotic environment. QT45 slashes that size requirement dramatically. At just 45 nucleotides, it falls within a range that some researchers believe could emerge from random chemical processes on early Earth.
The research team at the MRC Laboratory of Molecular Biology, led by Tjhung and senior author Philipp Holliger, demonstrated that QT45 could use trinucleotide triphosphate substrates to synthesize a copy of its own complementary strand under mildly alkaline conditions in eutectic ice, a partially frozen state where liquid water persists in thin channels between ice crystals. Those channels concentrate RNA molecules and their building blocks, potentially accelerating reactions that would be too dilute to proceed in open water.
“The ice acts almost like a natural concentrator,” Tjhung explained. “You get effective molarity increases that you simply cannot achieve in bulk solution at these temperatures.”
The work builds on decades of experiments showing that functional RNA molecules can be pulled from entirely random pools. A landmark 1995 study demonstrated that highly active RNA ligases could be evolved from unstructured sequences, establishing that catalytic ability does not require a designed starting point. QT45 extends that principle from ligation, the joining of RNA fragments, to polymerization, the stepwise copying of a template.
Why ice matters
The decision to run experiments in frozen conditions was not arbitrary. A 2013 study in Nature Chemistry showed that freeze-thaw cycles can support ribozyme polymerase activity and even drive molecular evolution. That earlier work, while conducted independently and on different ribozyme systems, provided broader support for the idea that icy environments could be productive settings for RNA catalysis, a line of reasoning the QT45 team drew on when designing their experiments.
Whether those conditions reflect what early Earth actually looked like is another question. The planet’s climate four billion years ago remains a subject of active debate. Some geochemists and planetary scientists argue that warm hydrothermal vents on the ocean floor were the most likely cradles for prebiotic chemistry, pointing to the energy and mineral catalysts available at those sites. Others contend that icy settings, perhaps on glaciated coastlines or in polar regions, offered advantages that warm water could not: concentrating fragile RNA molecules, slowing their degradation, and providing the physical compartmentalization that early replicators would have needed.
QT45 does not settle that debate, but it does provide concrete evidence that ice-based RNA chemistry can produce results that warm-water experiments have struggled to match at comparable molecular sizes.
The gap that remains
As coverage on Phys.org noted, QT45 achieves “near self-replication” rather than the fully autonomous, sustained copying that would allow a molecule to propagate indefinitely on its own. Several hurdles stand between the current result and that goal.
First, QT45 copies its complementary strand but has not been shown to complete the full replication cycle, producing a copy of itself from that complement without human intervention. Second, the ribozyme does not yet demonstrate error correction, meaning that copying mistakes would accumulate over successive generations and eventually destroy the sequence information needed for function. Third, the system has not undergone open-ended Darwinian evolution in the lab, the kind of sustained competition and adaptation that would signal a truly life-like process.
“We are not claiming we have made a self-replicator,” Holliger said. “What we have is a molecule that can do the hardest part of the job. Closing the remaining gap is the challenge for the next set of experiments.”
There is also an open question about how surprising QT45’s existence really is. Shorter random RNA pools should, in theory, yield fewer functional molecules. Finding polymerase activity in a 45-nucleotide sequence could mean that such catalytic motifs are more common in sequence space than researchers previously assumed, or it could reflect the effectiveness of the selection methods used. Resolving that question will likely require independent replication by other laboratories, which has not yet been reported as of May 2026.
What comes next for RNA world research
For scientists working on the origins of life, QT45 narrows the gap between laboratory chemistry and a plausible scenario for how biology began. The molecule shows that a very small RNA can perform the kind of copying that self-replication demands, and it does so under conditions that at least some researchers consider realistic for early Earth.
The next milestones are clear, if daunting: achieving full-length self-copying without experimental scaffolding, demonstrating that such a system can sustain itself through multiple generations, and showing that it can evolve. Each of those steps would bring the RNA world hypothesis closer to something that can be tested not just as a chemical possibility but as a historical explanation for how life on this planet got started.
The broader implications stretch beyond Earth. If small, self-replicating RNA molecules can emerge under icy conditions from simple chemical ingredients, that expands the range of environments in the solar system and beyond where the precursors of life might plausibly form. Icy moons like Europa and Enceladus, long considered candidates in the search for extraterrestrial life because of their subsurface oceans, become even more interesting if ice itself turns out to be part of the recipe.
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*This article was researched with the help of AI, with human editors creating the final content.
