The overwhelming majority of snails live in shells that coil to the right. But occasionally some are born with shells that turn the other way.

And then there was Jeremy, the garden snail with a left-coiled shell. His struggle to find a left-coiled mate made him famous. Just before dying in 2017, he was finally paired up, leaving behind a litter that was born all right.

How Jeremy and other chiral or mirror-image snails — including a few species that are all-left — turn out like this has long baffled scientists. Studying these snails offers clues to the evolution of body plans in many animals. It also could be important for understanding why approximately 1 in 10,000 people are born with situs inversus, a condition where their internal organs are flipped like a lefty snail’s shell.

Now scientists are turning to Crispr — the powerful gene editing tool — to figure out why some snails turn out this way. A team in Japan led by Reiko Kuroda, a chemist and biologist, has successfully used the technique to manipulate a single gene responsible for shell direction in a species of great pond snail. The research, published last week in the journal Development, offers definitive proof of the genetic underpinnings of handedness in this species, and could lead to clues about left- and right-handed mysteries in other organisms.