Frankenfish: genetically engineered fish in Taipei, July 2013.
PICHI CHUANG / REUTERS

The possibility of rewriting the genome of an organism, or even of an entire species, has long been the stuff of science fiction. But with the development of CRISPR (which stands for “clustered regularly interspaced short palindromic repeats”), a method for editing DNA far more precisely and efficiently than was possible with older technologies, fiction has edged closer to reality. CRISPR exploits an ancient system that allows bacteria to acquire immunity from viruses. It uses an enzyme called Cas9 to cut strands of DNA at precisely targeted locations, allowing researchers to insert new genetic material into the gap. 

CRISPR promises

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