CRISPR-Cas9 — Precision Gene Editing Becomes Possible
A paper published in June 2012 showed that a bacterial immune system could be reprogrammed to cut any chosen sequence of DNA, and biology acquired a general-purpose editing tool. CRISPR is a pattern of repeated sequences in bacterial genomes, noticed in 1987 and unexplained for two decades. It turned out to be an adaptive immune system: bacteria store fragments of the viruses that have attacked them and use them as templates to recognise and cut the same virus if it returns. Jennifer Doudna and Emmanuelle Charpentier showed that the cutting enzyme, Cas9, is guided to its target by a short RNA sequence, that the two RNA components could be fused into one, and that changing that sequence directs the enzyme anywhere. Feng Zhang and George Church demonstrated it in human cells within months, which produced a patent dispute that ran for a decade. The significance is cost and accessibility rather than novelty. Editing genomes was possible before with zinc fingers and TALENs, and it was slow and expensive; CRISPR made it something a graduate student could set up in an afternoon. The applications since are real: sickle-cell disease treated by editing patients' own blood stem cells and approved in 2023, engineered crops, gene drives that could eliminate malaria vectors and might not stop there. He Jiankui announced the birth of edited babies in China in 2018, was condemned internationally and imprisoned for three years. Doudna and Charpentier shared the Nobel Prize in Chemistry in 2020. The germline question is the one that has not been settled. Editing a body's cells affects one patient; editing an embryo affects everyone descended from it, and there is no international mechanism with the authority to permit or forbid it.
- Year: 2012 CE
- Category: Scientific
