Scientists in Portland, Ore., just succeeded in creating the first genetically modified human embryo in the United States, according to Technology Review. A team led by Shoukhrat Mitalipov of Oregon Health & Science University is reported to “have broken new ground both in the number of embryos experimented upon and by demonstrating that it is possible to safely and efficiently correct defective genes that cause inherited diseases.”

The U.S. team’s results follow two trials—one last year and one in April—by researchers in China who injected genetically modified cells into cancer patients. The research teams used CRISPR, a new gene-editing system derived from bacteria that enables scientists to edit the DNA of living organisms.

The era of human gene editing has begun.

In the short term, scientists are planning clinical trials to use CRISPR to edit human genes linked to cystic fibrosis and other fatal hereditary conditions. But supporters of synthetic biology talk up huge potential long-term benefits. We could, they claim, potentially edit genes and build new ones to eradicate all hereditary diseases. With genetic alterations, we might be able to withstand anthrax attacks or epidemics of pneumonic plague. We might revive extinct species such as the woolly mammoth. We might design plants that are far more nutritious, hardy, and delicious than what we have now.

But developments in gene editing are also highlighting a desperate need for ethical and legal guidelines to regulate in vitro genetic editing—and raising concerns about a future in which the well-off could pay for CRISPR to perfect their offspring. We will soon be faced with very difficult decisions about when and how to use this breakthrough medical technology. For example, if your unborn child were going to have a debilitating disease that you could fix by taking a pill to edit their genome, would you take the pill? How about adding some bonus intelligence? Greater height or strength? Where would you draw the line?

CRISPR’s potential for misuse by changing inherited human traits has prompted some genetic researchers to call for a global moratorium on using the technique to modify human embryos. Such use is a criminal offense in 29 countries, and the United States bans the use of federal funds to modify embryos.

Still, CRISPR’s seductiveness is beginning to overtake the calls for caution.

In February, an advisory body from the National Academy of Sciences announced the academy’s support for using CRISPR to edit the genes of embryos to remove DNA sequences that doctors say cause serious heritable diseases. The recommendation came with significant caveats and suggested limiting the use of CRISPR to specific embryonic problems. That said, the recommendation is clearly an endorsement of CRISPR as a research tool that is likely to become a clinical treatment—a step from which there will be no turning back.

CRISPR’s combination of usability, low cost, and power is both tantalizing and frightening, with the potential to someday enable anyone to edit a living creature on the cheap in their basements. So, although scientists might use CRISPR to eradicate malaria by making the mosquitoes that carry it infertile, bioterrorists could use it to create horrific pathogens that could kill tens of millions of people.

With the source code of life now so easy to hack, and biologists and the medical world ready to embrace its possibilities, how do we ensure the responsible use of CRISPR?

There’s a line that “A Prairie Home Companion” host Garrison Keillor uses when describing the fictional town of Lake Wobegon, where “all the children are above average.” Will we enter a time when those who can afford a better genome will live far longer, healthier lives than those who cannot? Should the U.S. government subsidize genetic improvements to ensure a level playing field when the rich have access to the best genetics that money can buy and the rest of society does not? And what if CRISPR introduces traits into the human germ line with unforeseen consequences—perhaps higher rates of cardiac arrest or schizophrenia?