A Crack in Creation: The New Power to Control Evolution

by Jennifer A. Doudna

A full 8 percent of the human genome—over 250 million letters of DNA—is a remnant of ancient retroviruses that infected ancestors of our species millennia ago.

TOMATOES THAT CAN sit in the pantry slowly ripening for months without rotting. Plants that can better weather climate change. Mosquitoes that are unable to transmit malaria. Ultra-muscular dogs that make fearsome partners for police and soldiers. Cows that no longer grow horns. These organisms might sound far-fetched, but in fact, they already exist, thanks to gene editing. And they’re only the beginning. As I write this, the world around us is being revolutionized by CRISPR, whether we’re ready for it or not.

Labradors are prone to some thirty genetic conditions, 60 percent of golden retrievers succumb to cancer, beagles are commonly afflicted with epilepsy, and Cavalier King Charles spaniels suffer from seizures and persistent pain due to their deformed skulls.66 These poignant medical problems haven’t kept humans from letting tastes dictate the genotype and phenotype of humankind’s best friend.

CRISPR offers the greatest hope to treat monogenic genetic diseases—those caused by a single mutated gene.

Every person experiences roughly one million mutations throughout the body per second,18 and in a rapidly proliferating organ like the intestinal epithelium, nearly every single letter of the genome will have been mutated at least once in at least one cell by the time an individual turns sixty.