On October 7, 2020, in a live-streamed announcement from Stockholm, the Royal Swedish Academy of Sciences gave the Nobel Prize in Chemistry to two women who had turned a bacterial immune system into a pair of programmable molecular scissors. Emmanuelle Charpentier and Doudna had shown that a defense mechanism Streptococcus pyogenes uses to shred invading viruses could be pointed at the DNA of any organism on Earth — human, wheat, mouse, mosquito — and made to cut a chosen sequence with the precision of a text editor finding a single word in a book.
It was the first time in the 119-year history of the chemistry prize that two women shared it, and the first all-female Nobel science pair ever. The tool they built has a name now familiar to anyone who reads about medicine: CRISPR-Cas9.
A defense system found in yogurt bacteria
The story begins not in a gene-therapy lab but in the microbial arms race that has been running for at least three billion years. Bacteria are hunted by viruses called bacteriophages. Phages inject their DNA into a bacterium and hijack it to make more phages. The bacterium usually dies.
Some bacteria, though, keep trophies. When a phage attack fails, the bacterium snips a small piece of the invader’s DNA — roughly 30 base pairs — and files it away in a stretch of its own genome called a CRISPR array. The acronym stands for Clustered Regularly Interspaced Short Palindromic Repeats. It looks, under sequencing, like a chain of identical spacer sections separated by short stretches of viral memory.
If the same phage attacks again, the bacterium copies the relevant memory into RNA, loads that RNA into a protein called Cas9, and sends the pair out like a guided missile. The RNA finds a matching sequence in the phage’s DNA. Cas9 cuts. The phage is disabled.
That mechanism was described in outline in the mid-2000s by researchers working on the industrial bacteria used to make yogurt and cheese. Food companies were interested for practical reasons: phage infections ruin fermentation vats. Nobody at that point was talking about editing human embryos.
The Puerto Rico coffee shop conversation
Charpentier, a French microbiologist, spent the 2000s moving between labs in New York, Vienna, and Umeå in northern Sweden, studying Streptococcus pyogenes — the bacterium behind strep throat. She was interested in its defense systems. In 2011 she published work identifying a small RNA molecule, called tracrRNA, that turned out to be the missing part of the CRISPR mechanism.
That same year, at a scientific conference in Puerto Rico, Charpentier asked Jennifer Doudna to have coffee. Doudna, a structural biologist at UC Berkeley, had spent two decades on RNA. She had been circling the problem of those strange repeating regions in bacterial genomes for years.
Over the next year, working across a nine-hour time difference, Charpentier’s group and Doudna’s group reconstituted the whole system in a test tube. Their paper appeared in 2012. It showed that Cas9, guided by a piece of RNA the researchers could design themselves, would cut any double-stranded DNA sequence they told it to. They also showed something even more useful: the two natural RNA components could be fused into a single “guide RNA,” simplifying the tool to two parts — one enzyme, one programmable RNA.
That is the trick that unlocked everything. Change the 20 letters of the guide RNA, and you change the address the scissors go to. A biology graduate student could order the components from a catalog by lunchtime.
From bacterial trick to universal tool
Earlier gene-editing methods existed. Zinc-finger nucleases and TALENs could also cut DNA at chosen sites. Both required custom-engineered proteins for every new target — a process that could take months and cost substantial resources per gene. CRISPR-Cas9 reduced that to a synthetic RNA oligo that could be ordered relatively inexpensively.
Within two years of the 2012 paper, labs around the world had used the system to edit yeast, zebrafish, fruit flies, mice, wheat, rice, tomatoes, monkeys and human cells in culture. Writing in The Conversation, a genome-engineering lab leader called CRISPR’s rapid revolutionizing of biotechnology and biomedical science “a rare occurrence in this scientific field” for a technology so young.
The Nobel citation was blunt about what that meant. Thanks to CRISPR-Cas9, the Royal Swedish Academy said, scientists can change the DNA of animals, plants and microorganisms with extremely high precision. The committee said the technology was already contributing to new cancer therapies and might make the dream of curing inherited diseases come true.
What the scissors actually do
Inside a cell, Cas9 loaded with its guide RNA drifts along DNA the way a reader’s finger might drift down a page, checking for a match. The DNA in a single human cell, uncoiled, would stretch about two meters. Cas9 has to find a specific 20-letter sequence in three billion base pairs. It does this by first recognizing a short signature called a PAM, then unzipping the local double helix and testing whether its guide RNA matches. Most sites fail the check in microseconds and the protein moves on.
When it finds a match, two nuclease domains within Cas9 snip both strands of the double helix. The cell’s own repair machinery rushes in. If nothing else is provided, the repair is sloppy — it re-glues the ends but often adds or drops a few letters, which knocks the gene out. That is often enough for research: you want to know what a gene does, so you break it and watch what happens.
Provide a template piece of DNA alongside the scissors, though, and the cell will sometimes use that template to patch the cut, effectively rewriting the sequence to whatever the researcher wants. That is the editing step. A single letter can be changed. A whole gene can be inserted. A disease-causing mutation can be reverted to its healthy version.
The first patients
The pace from bench to bedside was startling. By 2019, sickle cell disease patients had received CRISPR-edited stem cells that reactivated fetal hemoglobin, and their pain crises stopped. The U.S. Food and Drug Administration approved Casgevy, the first CRISPR-based medicine, for sickle cell disease in December 2023, and extended that approval to beta thalassemia the following January — roughly eleven to twelve years after the Charpentier-Doudna paper.
Other trials followed for hereditary blindness, hereditary angioedema, and transthyretin amyloidosis. Reporting on the Nobel announcement, Time noted that in the eight years since the 2012 paper, CRISPR had already been used to edit HIV genes out of human cells and to explore treatments for a congenital heart condition and for cancer-causing genes.
Agricultural applications moved even faster. Non-browning mushrooms. Pest-resistant rice. Tomatoes engineered to accumulate GABA. Beagles with doubled muscle mass created by knocking out a single myostatin gene. Mini-pigs bred as pets.
The patent war and the ethics debate
None of this happened without a fight over who owned it. The Charpentier-Doudna team filed their U.S. patent first in 2012. Feng Zhang, working at the Broad Institute of MIT and Harvard, filed later but got approval first — for the specific application of CRISPR-Cas9 in eukaryotic cells, meaning plants, animals and humans. That is where the money is.
The dispute has been grinding through the U.S. Patent and Trademark Office and the courts for more than a decade. In May 2025, a federal appeals court briefly revived the Nobel laureates’ case, vacating an earlier ruling that had favored the Broad Institute and sending the priority dispute back to the patent board for reconsideration. On remand, though, the Patent Trial and Appeal Board again sided with Broad, and in March 2026 the Nobel laureates lost yet another round, as Law360 reported, leaving the Broad Institute with the strongest position on the most lucrative use case even as Charpentier and Doudna held the Nobel.
The ethical stakes escalated even faster than the patent stakes. In November 2018, Chinese researcher He Jiankui announced he had used CRISPR to edit the genomes of twin girls at the embryo stage — the first germline-edited humans. He was sentenced to three years in prison. Doudna, who spoke to STAT the morning of the Nobel announcement, had been publicly warning about exactly this scenario since 2015, convening summits on heritable genome editing and calling for a moratorium.
The technology cuts DNA. It does not decide what to cut. That decision is left to people, and people, as the history of every previous transformative technology suggests, do not always choose wisely.
An accidental echo of 1938
There is a pattern in the history of science where a discovery about a specific system — how one bacterium fights one virus, how one uranium nucleus splits under a neutron — turns out to describe something universal. In December 1938, Otto Hahn and Fritz Strassmann found barium where they expected heavier elements, and Lise Meitner, on a snowy walk in Sweden, worked out that the uranium nucleus had split. She borrowed a word from biology and called it fission. Within seven years the physics of that quiet accident had reshaped geopolitics.
CRISPR is running on a comparable arc, minus the mushroom clouds. A bacterial curiosity in 2005. A test-tube demonstration in 2012. A Nobel in 2020. An approved medicine in 2023. Whole categories of inherited disease now imaginable as one-time fixes rather than lifelong management.
What Charpentier did next, what Doudna did next
Charpentier founded her own research institute, the Max Planck Unit for the Science of Pathogens in Berlin, and co-founded CRISPR Therapeutics, the company behind Casgevy. Doudna founded the Innovative Genomics Institute at Berkeley and has co-founded several companies, including Mammoth Biosciences and Caribou Biosciences. Both have spent the years since the prize working on cheaper, faster, more accurate versions of the tool — smaller Cas proteins that fit into viral delivery vectors, base editors that change single letters without cutting both strands, prime editors that can rewrite short sequences directly.
The 2020 prize came with 10 million Swedish kronor, split evenly, and no in-person ceremony. Stockholm’s banquet was canceled because of COVID-19. Charpentier received her medal in Berlin. Doudna received hers in Berkeley. Both events were televised.
Somewhere in a research freezer in Umeå, or in the sequencing archive of a Danish yogurt company, or in the working memory of a Streptococcus cell dividing right now in someone’s throat, the original spacers are still there — small viral souvenirs, filed away in a stretch of bacterial DNA that no one thought was interesting until two chemists realized it was a pair of scissors and asked what else it could cut.
