CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from DNA fragments of bacteriophages that had previously infected the prokaryote. They are used to detect and destroy DNA from similar bacteriophages during subsequent infections, playing a key role in the antiviral defense system of bacteria.

CRISPR technology has been adapted for use in the laboratory from naturally occurring genome editing systems found in bacteria. The CRISPR-Cas9 system consists of two key molecules that introduce a change (mutation) into the DNA: an enzyme called Cas9, which acts as a pair of ‘molecular scissors’ that can cut the two strands of DNA at a specific location in the genome, and a guide RNA molecule that binds to the target DNA sequence and directs Cas9 to the right location. This allows geneticists and medical researchers to edit parts of the genome by removing, adding, or altering sections of the DNA sequence.

CRISPR technology has many potential applications, including in the food and farming industries to engineer probiotic cultures and to immunize industrial cultures against infections. In the field of biomedical research, CRISPR has greatly reduced the time and expense of developing animal models with specific genomic changes. There are also clinical applications in human trials now, including for engineering T cells outside of the body for CAR-T cancer therapy and for editing retinal cells for Leber’s congenital amaurosis 10, an inherited form of blindness. However, CRISPR technology has important limitations, including difficulties in delivering the CRISPR/Cas material to mature cells in large numbers, not being 100% efficient, and the potential for off-target effects.