Every cell in every organism on Earth copies DNA in the same manner. Except for one bacterial protein—quietly doing something scientists had never witnessed before.
Your DNA has never been produced from nothing.
Consider it like a recipe—handed down from parent to child across countless generations, stretching back 4 billion years to the earliest life on Earth. Tweaks and modifications have accumulated along the way, but it has always been copied from something that already existed.
That is the single rule that has persisted throughout: to create DNA, you need existing genetic material to replicate from.
Scientists have just discovered a protein that violates this rule.
A mechanism never seen before
"It was quite a surprise!" Alex Gao, a biochemist at Stanford University in California and senior author of the study, told DW.
His team was investigating how bacteria defend themselves against viruses when they identified something unexpected: a protein called Drt3b that builds DNA without any template to copy from. It uses its own shape as a mold to click the correct building blocks into position.
"We didn't believe it until we saw the cryo-EM structure [...] That was the moment it really clicked for us," he said—referring to cryo-electron microscopy, a technique that images molecules at near-atomic resolution.
The findings were published in the journal Science in April.
So how does it actually work?
DRT3—the full system studied by Gao's team—operates in two steps.
DNA is double-stranded: think of it like a zipper, with two sides that fit together.
One side is built in a conventional way, with a protein called Drt3a using a small piece of genetic material as a template to construct one strand.
The other side is where things become unusual. A second protein, Drt3b, must build the other side of that zipper—but does so without a template. Instead, specific parts of the protein itself serve as the guide, locking onto the correct DNA building blocks or "nucleotides" one by one until the strand is complete. And that is what we thought was impossible—at least not in this manner.
Other proteins have done something similar before—but only in short fragments, like writing a sentence. Drt3b writes an entire paragraph. It is the first known protein to produce a long, sequence-specific strand of DNA using nothing but its own structure as a guide.
Why does it matter?
"The research is groundbreaking," said Philip Kranzusch, a biochemist at Harvard Medical School who was not involved in the study.
That is because scientists have been studying DNA since the 1950s, and bacteria have been quietly doing something they never imagined was possible. Which raises the question: what else are we overlooking?
There is also a practical angle. If scientists could engineer Drt3b to produce other DNA sequences, it might one day serve as a tool for building custom DNA molecules—without needing a template to copy from.
But we are not there yet. "We do not yet know if it can be reprogrammed or engineered in a useful way," Rafael Pinilla-Redondo, an assistant professor at the Section of Microbiology at the University of Copenhagen, told DW.
So does this break the rules of biology?
The discovery has sparked debate around what is called the "central dogma of biology"—the idea that genetic information flows from DNA to RNA to protein, but never from protein back into DNA. If a protein can write a DNA sequence, does that violate the rule?
"No, I would not say the central dogma has been broken," said Pinilla-Redondo. What the study shows is a protein helping to build a short, repetitive DNA sequence in a very specific context—not proteins generally rewriting genetic code. "The exciting part is not that the rules of biology have collapsed. It is that evolution has found a very unexpected way to build a DNA molecule," he said.
But what does the DNA actually do?
Scientists do not fully know yet.
The leading hypothesis is that the DNA acts as a kind of molecular sponge—soaking up essential components of the attacking virus and neutralizing it. But Alex Gao is careful about how firmly he holds that idea. "That's currently our leading hypothesis, but we're certainly open to alternative models," he said.
Pinilla-Redondo agrees the mechanism is still far from understood. "Is the DNA a decoy, a signal, a scaffold, or a toxic molecule? That is the key mystery," he said.
Is this the next CRISPR?
CRISPR—the molecular scissors that allow scientists to cut and edit DNA with unprecedented precision—was itself first discovered as a quirky bacterial defense system. It has since transformed medicine, including the first approved gene therapy for sickle cell disease in 2023.
Sounds familiar, right? But will it be a similar story with DRT3?
Probably not—at least not yet. "CRISPR is a once-in-a-generation breakthrough that revolutionized biotechnology," said Gao. "While it is early to predict applications of DRT3, we are most excited about DRT3 for expanding our understanding of the mechanisms of DNA synthesis."
A glimpse into microbial dark matter
"The field of bacterial immunity is exploding," said Pinilla-Redondo. Experimental research on these bacterial defense systems has only just begun—and the diversity of mechanisms being uncovered is striking, with multiple research groups around the world independently making similar findings.
For Gao's team, this discovery is less an ending than a beginning. Bacteria have spent billions of years fighting viruses, quietly evolving molecular tricks that we are only beginning to discover. How many more are out there?
"It points to a vast reservoir of uncharacterized biology within microbial 'dark matter,' where fundamental mechanisms likely remain undiscovered," said Gao.
Edited by: Frank Lee