doi.org/10.1126/science.adt2760
Credibility: 999
#QT45
One of the great theories about how life began on Earth is the RNA world hypothesis
It suggests that, in the beginning, before complex cells with DNA and proteins existed, RNA molecules were the first to be able to copy themselves, giving rise to the process of evolution.
RNA is similar to DNA, but it usually exists in single-stranded form.
It doesn’t store information as well as DNA because it’s less stable, but it has an incredible advantage: it can fold and function like enzymes, accelerating chemical reactions.
Therefore, for decades scientists have imagined that RNA molecules capable of catalyzing their own copying could have been the starting point of life.
The problem is that finding or creating such RNA has always been very difficult.
Researchers thought that these molecules would need to be large and complex to replicate, but large molecules are difficult to copy and unlikely to arise on their own in the chemical soup of early Earth.
Short molecules, on the other hand, arise more easily, but no one could prove that they would have sufficient capacity for replication.
Now, a team led by Philipp Holliger of the Medical Research Council’s Laboratory of Molecular Biology in the UK has changed that.
They created a surprisingly small RNA, with only 45 nucleotides (the “letters” that make up RNA), named QT45 – something like “Very Small 45”.
They started by generating trillions of short random sequences (20 to 40 nucleotides) and selected those that could perform basic reactions, such as joining pieces of RNA.
Then, they joined these promising sequences and subjected them to several rounds of evolution in the laboratory: they randomly changed parts and chose the versions that worked best.
The result was QT45. Under special conditions – alkaline water slightly above freezing, similar to icy environments with geothermal activity, such as in ancient Iceland – this molecule uses an RNA strand as a template to build the complementary strand, joining small pieces of two or three nucleotides.
It can make a faithful copy of its own complementary sequence.
Even more impressive: QT45 also uses this complementary strand as a template to produce copies of itself.
This means that, for the first time, an RNA molecule has demonstrated the two essential reactions for self-replication: manufacturing the opposite strand and, from it, recreating the original.
For now, the two steps do not happen simultaneously in the same container, and the process is slow and has a low yield.
But Holliger explains that this is not surprising, since it is a simple system.
The team plans to continue evolving the molecule in the laboratory and test conditions such as freeze-thaw cycles to see if the two reactions can occur together.
The most exciting thing, according to him, is that once replication begins, the system self-optimizes.
Errors in copying generate variations, and those that work best multiply more, initiating a kind of molecular natural selection.
Independent experts have praised the advance.
Sabine Müller, from the University of Greifswald in Germany, called the results exceptional and a major step towards a fully self-replicating RNA.
Zachary Adam, from the University of Wisconsin-Madison, highlighted that finding a 45-nucleotide sequence with these capabilities amidst a vast number of possibilities shows how ribozyme polymerases may be more common than previously thought.
On the early planet, molecules like QT45 could have replicated in environments with ice, hot springs, and freeze-thaw cycles, creating favorable pH gradients.
Some type of compartment-such as pockets of meltwater in the ice or vesicles formed by fatty acids-would help keep the components together.
This discovery reinforces the idea that life may have arisen simply, from small, self-replicating RNA, paving the way for more complex forms over time.
Published in 03/23/2026 21h04
Text adapted by AI (Grok) and translated via Google API in the English version. Images from public image libraries or credits in the caption. Information about DOI, author and institution can be found in the body of the article.
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