Story 02 · Genes and medicine
The bacterial defence that became a gene editor
Scientists turned a system bacteria use to fight viruses into a tool that can cut DNA at a chosen spot, and in 2023 the first CRISPR-based treatment was approved for sickle cell disease.
- CRISPR-Cas9
- Berkeley, United States, and Umeå, Sweden
- 2012
- 3 min read
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Before you readWhat would you do?
A website offers a "CRISPR anti-ageing injection" for a large fee, with glowing reviews but no published trials or regulator approval. What is the wisest step?
Pick an answer now. The file tells you whether you were right.
01The file in one minute
1From bacteria
Bacteria use CRISPR and proteins like Cas9 to recognise and cut the DNA of viruses that attacked them before.
2A new tool
In 2012 Doudna and Charpentier showed Cas9 could be guided to cut DNA at a chosen place. They won the 2020 Nobel.
3First treatment
In late 2023 the UK and US approved Casgevy, which edits patients' own blood stem cells, for sickle cell disease.
4The lesson for AI
A powerful tool still needs testing, clear rules and people who understand its limits.
02Timeline
1990s to 2000s
Scientists study the CRISPR defence system in bacteria.
August 2012
Doudna, Charpentier and colleagues show Cas9 can be programmed to cut DNA.
2020
Doudna and Charpentier receive the Nobel Prize in Chemistry.
November 2023
The UK authorises Casgevy, the first CRISPR-based treatment.
December 2023
The US approves Casgevy for sickle cell disease.
03The story
Bacteria are attacked by viruses too. Many store short pieces of viral DNA in a part of their genome called CRISPR, and use them with a protein such as Cas9 to recognise and cut the same virus if it returns. Researchers spent years working out how this natural defence works.
In August 2012, a team led by Jennifer Doudna and Emmanuelle Charpentier showed in the journal Science that Cas9 could be guided by a designed piece of RNA to cut DNA at almost any chosen place. Other groups soon showed it working in human and animal cells. Doudna and Charpentier received the 2020 Nobel Prize in Chemistry.
In November 2023 the UK medicines regulator authorised Casgevy, a treatment that edits a patient's own blood stem cells, for sickle cell disease and a severe form of beta thalassemia. The US approved it for sickle cell disease in December 2023. The treatment is complex: cells are taken out, edited in a lab, and returned after strong chemotherapy, and it is very expensive.
04What the science says
CRISPR is precise compared with older methods, but it is not perfect. It can sometimes cut in the wrong place or cause changes nobody planned, so every use needs testing. Treatments that edit a patient's own body cells, which are not passed to children, are accepted far more widely than edits to embryos, which would be.
The AI angle: CRISPR, like AI, is a powerful general tool that does one narrow thing very well. Its value depends on careful testing, clear rules and people who understand its limits.
The idea behind this caseLesson: What is AI, really? →
05What to take from it
- Separate what a new tool has been shown to do in approved treatments from what headlines say it might do one day.
- Ask whether a new medical treatment has been approved by a regulator and tested in published trials.
- Be wary of clinics or websites selling "gene therapy" that is not approved.
- If you or a family member has a genetic condition, ask a specialist doctor whether any approved treatments or trials might fit.
07 — Sources
- A Programmable Dual-RNA-Guided DNA Endonuclease in Adaptive Bacterial Immunity · Science · 2012-08-17
- The Nobel Prize in Chemistry 2020 · NobelPrize.org · 2020
- MHRA authorises world-first gene therapy that aims to cure sickle-cell disease and transfusion-dependent β-thalassemia · UK Medicines and Healthcare products Regulatory Agency · 2023-11-16