CRISPR — Editing the Instructions
Bacteria have been keeping a filing cabinet of the viruses that have attacked them, along with molecular scissors set to cut anything matching the file. Humans noticed this, borrowed it, and can now rewrite the genome of essentially anything, which is either the most important tool of the century or a very well-documented way to find out.
Why it was classified
It never was, and that is part of the story. The odd repeating DNA sequences were first reported by Yoshizumi Ishino's group in 1987 as an unexplained curiosity in E. coli. It took until the mid-2000s to work out they were an adaptive immune system. In 2012 Jennifer Doudna and Emmanuelle Charpentier published the demonstration that the Cas9 enzyme could be programmed with a guide RNA to cut a chosen DNA sequence in a test tube; Feng Zhang's group and others showed it working in human cells the following year. Doudna and Charpentier shared the 2020 Nobel Prize in Chemistry.
Why it matters
Cutting DNA was possible before; cutting it cheaply, precisely and on a laptop budget was not. Casgevy, a CRISPR therapy for sickle cell disease and beta thalassaemia, was approved in the UK and US in late 2023 — an actual licensed medicine derived from a bacterial grudge. The other side of the ledger arrived in November 2018, when He Jiankui announced the birth of twin girls whose embryos he had edited, an act condemned worldwide as a serious ethical and scientific violation, for which he was imprisoned in China for three years. The technology's defining feature is its accessibility, which is simultaneously the reason it will treat inherited disease and the reason there is a permanent international argument about what counts as an acceptable edit.
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