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5 Reasons Gene Editing Is Both Terrific and Terrifying

New ways to easily snip and tuck genes have put scientists in the middle of a fast-accelerating ethical debate.

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Extinct species like the woolly mammoth could be brought back by tinkering with their recovered genes—though no one knows whether this could have unintended consequences.


The idea of tinkering with the genes we pass to our children has long been the stuff of science fiction. But scientists are rapidly solving the technological challenges, and expect such gene editing will soon be feasible.

A three-year-old technique called CRISPR/Cas9 is so effective at cutting and adding genes that researchers all over the world have adopted it in their labs. Earlier this year, researchers in China edited genes in a nonviable human embryo to try to treat an inherited blood disease, and ended up with a lot of unintended—and potentially dangerous—changes.

This week, a high-profile group of researchers, ethicists and advocates convened in Washington, D.C., to discuss the ethics of editing human genes. In particular, they're concerned about changes to human eggs, sperm or embryos—known as the human germline.

If you edit the genes of an adult, the changes don’t get passed down to that person's children. But editing genes in the germline would affect the child’s own egg and sperm, so the genetic changes are inherited.

The organizing committee ended the discussion by issuing a statement saying that “it would be irresponsible to proceed with any clinical use of germline editing” until more safety and effectiveness research can be done, risks and benefits weighed, and a social consensus reached. The group called for regulatory oversight of use in people, and concluded that “as scientific knowledge advances and societal views evolve, the clinical use of germline editing should be revisited on a regular basis.”

In Washington, scientists and ethicists talked about science, ethics, human rights, government relations and Aldous Huxley’s futuristic 1932 novel Brave New World, offering five basic reasons that gene editing is exciting—but scary:

1. Curing disease

By eliminating genes that cause disease, doctors could treat a wide range of illnesses, from heart disease to Alzheimer’s.

Scientific challenges remain, such as making sure that the right gene—and only the right gene—gets changed. But gene therapy is now being used to treat eye disease, and early trials suggest that it may be able to treat the blood disorders beta thalassemia and sickle cell anemia, said Fyodor Urnov of Sangamo BioSciences, a leader in blood disease research.

Even for this seemingly noble cause, there are moral challenges: namely, which conditions to treat. And not everyone necessarily wants to be “cured.”

To some people labeled with disabilities, “editing may be more akin to getting pushed through a shredding machine,” said Ruha Benjamin, an African-American Studies and bioethics professor at Princeton University.

2. Stopping inherited disease in its tracks

Diseases that are passed down in families, like Huntington's and Tay-Sachs, might one day be simply snipped out of the family line.

Though we can already screen for some genetic diseases and avoid them using in vitro fertilization, new CRISPR methods could potentially make much more complex edits. Harvard Medical School geneticist George Church recently showed that with the new CRISPR methods, he could edit 60 embryonic pig genes simultaneously. This may be harder in people, though, and since we don’t know the full roles of most of our genes, we can’t know the risks involved in editing them.

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People who carry a genetic risk for Alzheimer’s might some day be able to benefit from new efforts to change genes.


Rudolf Jaenisch, a stem cell biologist at MIT and the Whitehead Institute, raised another ethical concern: Is it morally acceptable to edit the genes of healthy children in the hopes of preventing unhealthy ones? In his research on mouse embryos, he’s found that he can’t edit the genes of diseased mice without also affecting the genes of mice that would otherwise be healthy.

In trying to prevent a genetic mutation in sick children, doctors would have to introduce a gene mutation into healthy ones. Such a mutation would carry forward into the human population, and no one knows whether it would have an unintended effect.

3. Creating a better you

Theoretically, gene editing could also be used to make so-called designer babies. Traits governed by a small number of genes would be the most straightforward to manipulate, such as muscularity, eye color, height, and memory, said George Daley, a stem cell biologist at Harvard Medical School.

Editing genes for more complex traits like intelligence would be more difficult or impossible. “You don’t know what else you’re going to get,” Sheldon Krimsy of Tufts University, who writes about science and ethics, said in an interview. “The genome is an ecosystem. Everything is in some kind of balance. You try to maximize one quality and you may affect another one.”

What's more, if a change is introduced into the human population, and can be inherited, it could be hard to remove—and won't stay put in a particular community or country.

Unlike curing disease, genetic enhancement would be morally reprehensible, said Marcy Darnovsky, who heads the nonprofit Center for Genetics and Society.

She worries that parents will feel pressured to “improve” their kids and that wealthy families will have greater access than poor ones. “There would be fertility clinics vying to sell the latest upgrades." And parents might be pressured to ‘give their child the best start in life.’

4. Saving endangered species

The same technology used to edit human genes can be used on animals. This could mean protecting a species like the Tasmanian devil, now endangered by an infectious cancer, or engineering the East Coast's chestnut trees to resist the chestnut blight that has devastated their growth.

“We’re faced with the sixth great mass extinction," Gary Roemer, a wildlife ecologist at New Mexico State University, said in an interview, "and this allows us to avert or perhaps just postpone the decline of certain species.”

On the other hand, he and others were horrified at the possibility that someone might use gene editing as justification for putting off a species rescue “because we can always solve the problem later.”

"We’re faced with the sixth great mass extinction." —Ecologist Gary Roemer

“I’m very much against that kind of arrogance,” said Stuart Pimm, the Doris Duke professor of Conservation Ecology at Duke University. “We should be good stewards. We should look after biodiversity.”

5. Resurrecting extinct species

Gene editing could even be used to bring back extinct species, or at least parts of them, for example by mixing genes from extinct species back into existing ones. A group called The Long Now Foundation supports these scientific efforts, and hopes first to bring back the passenger pigeon and then the wooly mammoth.

De-extinction could also resurrect traits lost to commercial breeding, like the great natural taste of tomatoes, bioethicists, R. Alta Charo of the University of Wisconsin-Madison, and Henry Greely of Stanford, wrote in a paper published Wednesday.

But, they write, somewhat tongue-in-cheek, gene editing could also be used to blend or make new species “on a whim” or for commercial or artistic purposes. “Why should we not expect dwarf elephants, giant guinea pigs, or genetically tamed tigers? Or—dare we wonder—the billionaire who decides to give his 12-year-old daughter a real unicorn for her birthday?”

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