CRISPR is a gene-editing tool borrowed from bacteria, which use it as an immune memory: they store viral DNA fragments between repetitive sequences and deploy the Cas9 protein to cut matching invaders. In 2012 Jennifer Doudna and Emmanuelle Charpentier showed Cas9 could be programmed to cut DNA at any chosen spot — 2020 Nobel Prize in Chemistry.
The discovery turned genetic engineering from a million-dollar craft into bench-top routine: cut the DNA, and the cell's own repair machinery can disable a gene or paste in a new sequence. Medicine, agriculture and basic research were transformed within a decade — and so was the ethical debate, when the first gene-edited babies were announced in 2018.
