CRISPR can rewrite our genetic code: Best ideas of the century

“The pain was like being struck by lightning and hit by a freight train all at the same time,” Victoria Gray told New Scientist in 2023. “Now everything is different for me.”

Gray used to experience severe episodes of sickle cell disease, but in 2019 she was effectively cured by a revolutionary technique that enables changes to be made to specific bits of our DNA: CRISPR gene editing. In 2023, that experimental treatment became the first approved CRISPR therapy.

There are hundreds of clinical trials of CRISPR-based treatments now under way, and this is just the start. CRISPR could help treat all kinds of diseases, not just genetic conditions. For instance, a single dose of CRISPR could reduce your risk of heart attacks and strokes by permanently lowering your cholesterol levels.

And while it isn’t yet safe enough to attempt, it does seem likely that in the future, CRISPR will be routinely used to alter our children’s genomes to reduce their risk of common diseases.

CRISPR is also starting to transform farming by making it much easier to develop crops and livestock that are disease-resistant, adapted to warmer conditions or better for eating.

Given all this, there is no doubt that CRISPR is one of the very best ideas of the 21st century. Its power lies in its ability to correct “spelling mistakes” in DNA. There are two parts to this: first, you have to get your gene-editing tool to the right place in the genome, like moving your cursor to the right spot in a long document on a computer. Next, you make the change.

Microbes use this mechanism in their battle with other microbes and, prior to 2012, biologists had discovered many natural gene-editing proteins. However, each one targeted just one location, or sequence, in the genome. To edit a different spot, the only option was to redesign the part of the protein that binds to DNA to target another sequence, a laborious process that took years.

But it turns out that bacteria have evolved a big family of gene-editing proteins that don’t bind to DNA directly. Instead, they hook up with a piece of RNA – a cousin of DNA – and search for sequences that match the RNA. And making RNA takes days, not years.

In 2012, Jennifer Doudna at the University of California, Berkeley, and her colleague Emmanuelle Charpentier at the Max Planck Institute for Infection Biology in Berlin showed how one of these gene-editing proteins, called CRISPR Cas9, could be made to target any desired sequence by adding the right form of “guide RNA”.

There are now thousands of variants of CRISPR being used for many purposes, but all rely on guide-RNA targeting. It is a world-changing technology, for which Doudna and Charpentier were awarded a Nobel prize in 2020.