Last century, the world was upended when science breached the inner sanctum of atoms and created the A-bomb. Today we are hacking into the inner sanctum of living cells and the consequences, for better and worse, spell the end of life as we know it.

First, the good: using CRISPR and other tools to treat genetic diseases, of which there are thousands – everything from cystic fibrosis, hemophilia, and breast cancer to diabetes, autism, and even obesity.

Patients with Duchenne Muscular Dystrophy (DMD), for instance, have a defective gene that fails to produce enough dystrophin, a key muscle protein. Recently, doctors at Nationwide Children’s Hospital in Columbus, Ohio, injected healthy genes into four DMD boys and obtained very encouraging results.

As I write this, renegade genetic engineers in California and Minnesota are creating pig-human and sheep-human chimeras whose vital organs are human. They are doing it against the wishes of and without any funding from the National Institutes of Health (NIH). But they’re reportedly motivated by a noble cause: to create a limitless source of body parts for patients in need of them.

But what if the human cells in these illicit chimeras proliferate beyond their vital organs – to their brains, for instance? The resulting creatures, possibly capable of human thought, could no longer be considered just pigs.

“We are not near the island of Dr. Moreau, but science moves fast,” warns David Resnik, an ethicist at the NIH. “The specter of an intelligent mouse stuck in a laboratory somewhere screaming ‘I want to get out’ would be very troubling to people.”

I love science and trust in its motivating desire to understand the universe and improve the human condition.

But if we’ve learned anything from our hacking the atomic nucleus, it’s this: the sketchy and unnerving consequences – such as nuclear power plants and H-bombs – severely overshadow the good ones, such as nuclear medical devices that treat cancers and routinely save lives. Witness our current nail-biting efforts to keep nukes out of the hands of North Korea and Iran.

Although I foresee a great deal of good coming from genetic engineering, I’m inclined to commiserate with the late Erwin Chargaff, eminent Columbia University biochemist and DNA research pioneer. “The nucleus of the atom, the nucleus of the cell,” he wrote in “Heraclitean Fire: Sketches from a Life Before Nature.” “In both instances do I have the feeling that science has transgressed a barrier that should have remained inviolate.”