A Crispr calf is born. It’s definitely a boy

UC Davis scientists spent years editing a sex-determining gene into bovine embryos. In April, Cosmo arrived—and his DNA reveals how far the field has to go.

THE CALF WAS late. His due date, March 30, had come and gone. At first, Alison Van Eenennaam chalked it up to male calves tending to arrive a day or two on the tardy side. As the week wore on, the animal geneticist reminded herself that gene-edited embryos—like the one that had been growing inside Cow 3113 for the past nine months—can take a little longer to signal to their surrogate mothers that they’re ready to be born. But by the following week, two false alarms at the UC Davis Beef Barn later, with still no signs of impending labor, Van Eenennaam’s fraying nerves had had enough. She called the vet. It was time to induce.

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Meet Cosmo, the gene-edited Crispr calf