CRISPR-Cas9 is a programmable gene-editing system that uses a short guide RNA to direct the Cas9 enzyme to a matching DNA sequence, where Cas9 makes a precise cut so the sequence can be altered. As a research tool, it lets laboratories target specific genes for study; the foundational work on harnessing it as a programmable system is associated with Jennifer Doudna and Emmanuelle Charpentier.
This article describes the mechanism and its use as a research method. It makes no clinical or therapeutic claims; the framing throughout is how CRISPR works as a laboratory tool and how its use is documented and governed.
The bacterial origin of CRISPR
CRISPR originates as a natural defence system in bacteria. The acronym stands for clustered regularly interspaced short palindromic repeats — segments of DNA that, together with associated (Cas) proteins, help bacteria recognise and cut the DNA of invading viruses. Researchers adapted this natural recognise-and-cut machinery into a programmable laboratory tool by supplying a custom guide RNA.
How the guide RNA and Cas9 work together
The system has two essential parts. The guide RNA is a short RNA sequence designed to match a chosen DNA target. The Cas9 enzyme is the molecular scissors that binds the guide RNA, locates the matching DNA, and introduces a cut at that site.
| Component | Role |
|---|---|
| Guide RNA | Programmable sequence that directs the system to a specific DNA target |
| Cas9 enzyme | Binds the guide RNA and cuts the DNA at the targeted site |
| Target DNA | The genomic sequence selected for study or modification |
Because the guide RNA can be reprogrammed simply by changing its sequence, the same Cas9 enzyme can be directed to many different targets. That programmability is what makes CRISPR a flexible research method, and the precise notation of target sequences relies on standard conventions like those in the CASRAI dictionary.
CRISPR as a research method
In the laboratory, CRISPR-Cas9 is used to investigate gene function — for example, by disabling a gene and observing the result. Treating CRISPR as a method places it firmly within the research lifecycle: it must be planned, documented, executed and reported like any other experimental technique. Recording the exact guide-RNA sequences, target sites and reagents used is essential for others to interpret the work.
Reproducibility and governance considerations
Reproducibility depends on complete reporting. Independent researchers can only repeat or build on a CRISPR experiment if the guide-RNA design, target sequence, delivery method and verification approach are fully described. This connects CRISPR reporting to the standards-led thinking across our reproducibility coverage and to method-reporting frameworks such as those discussed in our guide to gene-expression reporting standards.
Governance is the second consideration. Research use of gene editing is subject to institutional oversight and ethical review, and provenance — what was edited, how and under what approvals — should be documented. The same governance discipline appears in our coverage of stem-cell research registries and governance, and stable identifiers help link methods to outputs as set out in our note on persistent identifiers in 2026. For documentation practice, see our guidance for authors.
Frequently asked questions
How does CRISPR-Cas9 work?
A short guide RNA is designed to match a chosen DNA sequence. The Cas9 enzyme binds the guide RNA, finds the matching DNA, and cuts it at that site, allowing the targeted sequence to be studied or altered in the laboratory.
Where does CRISPR come from?
CRISPR originates as a natural defence system in bacteria that recognises and cuts the DNA of invading viruses. Researchers adapted this recognise-and-cut machinery into a programmable laboratory tool by supplying a custom guide RNA.
Who is associated with developing CRISPR as a tool?
The foundational work on harnessing CRISPR-Cas9 as a programmable gene-editing system is associated with Jennifer Doudna and Emmanuelle Charpentier.
What needs to be reported for a CRISPR experiment to be reproducible?
Complete reporting should include the guide-RNA design and sequence, the target site, the delivery and verification methods, and the reagents used, so that independent researchers can interpret and repeat the work.
