CRISPR and the Splice to Survive | The New Yorker

April 28, 2021

A few feet away from the detoxed toads, Spot and Blondie were sitting in their own tank, an even more elaborate affair, with a picture of a tropical scene propped in front for their enjoyment. They were almost a year old and fully grown, with thick rolls of flesh around their midsections, like sumo wrestlers. Spot was mostly brown, with one yellowish hind leg; Blondie was more richly variegated, with whitish hind legs and light patches on his forelimbs and chest. Cooper reached a gloved hand into the tank and pulled out Blondie, whom she’d described to me as “beautiful.” He immediately peed on her. He appeared to be smiling malevolently. He had, it seemed to me, a face only a genetic engineer could love.

To guard against a Vonnegutian catastrophe, various fail-safe schemes have been proposed, with names like killer rescue, multi-locus assortment, and daisy chain. All of them share a basic, hopeful premise: it should be possible to engineer a gene drive that’s effective but not too effective. Such a drive might be engineered so as to exhaust itself after a few generations, or it might be yoked to a gene variant that’s limited to a single population on a single island. It has also been suggested that if a gene drive did somehow manage to go rogue it might be possible to send out into the world another gene drive, featuring a “Cas9-triggered chain ablation”—or catcha—sequence, to chase it down. What could possibly go wrong? “}}