Designer babies crawl closer

Super crops and healthy productive farm animals; mosquito populations controlled without pesticides; a cure for cancer … This fantasy world has loomed since the 1970s when we first learnt how to edit DNA, the code of life.

But the technology to do so turned out to be cumbersome, costly and unreliable. The failure rate in animal tests was so high that fixing a person’s genetic disease became out of the question.

This began to change with the discovery of proteins purpose-built to modify DNA: so-called zinc finger nuclei in the 1990s and TALENS in 2009. The success rate climbed high enough to start clinical trials: zinc finger nuclei were used to make human immune cells resistant to HIV, and TALENS was used to repair the gene that causes Severe Combined Immunodeficiency (SCID). 

And then scientists uncovered a new DNA-editing strategy in bacteria, used to edit out invading viruses. It was a modular system composed of proteins and RNA, termed CRISPR. And like all modular systems, it offered amazing versatility. The protein module (CAS 9) was a missile that...