Inside the garage labs of DIY gene hackers, whose hobby may terrify you

When the future of genetic engineering arrived on Sebastian Cocioba’s doorstep, it was affixed to the back of a postcard from Austria with a little bit of packing tape.

Cocioba is a 25-year-old college dropout whose primary interest is tinkering with plant genetics in a lab he cobbled together from eBay. The lab is located in the spare bedroom of his parent’s lavish apartment in Long Island City, across the river from Manhattan. A few months ago, an internet friend from an online bio-hacking forum had sent him the lab’s latest addition: attached to that postcard was Crispr-Cas9.

Deposited onto a flimsy fragment of filter paper and wrapped in plastic, it looked like a tab of acid. But inside that crude packaging was the key to an incredibly precise DNA-editing technology that will revolutionize the world.

Crispr—a memorable acronym for the mouthful, “clustered regularly-interspaced short palindromic repeats”—gives scientists an unprecedented ability to decrypt and reorder genes, opening up a dazzling and terrifying universe of possibilities. This year, a top national security official called gene-editing a weapon of mass...