The question could hardly be more profound. Having stumbled upon a simple means to make precise changes to the code of life, should humans take control of their genetic fate, and rewrite the DNA of future generations?

Once an idea explored only in fiction, the prospect is now a real one. The inexorable rise of gene editing has put the technology in labs across the globe. The first experiments on human embryos have been done, in a bid to correct faulty genes that cause disease.



To thrash out an answer, or at least find common ground, an international group of experts will descend on Washington DC next week for a three day summit. Convened with some urgency by the US, UK and Chinese national academies, the meeting is billed as a “global discussion”. It is a chance to take stock of a revolutionary technology that has the power to do good, and the potential to wreak havoc.



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“This new technology for gene editing, that is, selectively inserting and removing genes from an organism’s DNA, is spreading around the world,” says Ralph Cicerone, president of the US National Academy of Sciences, where the summit will take place. With the number of experiments ballooning, the uses and risks the technology brings must be worked through now, he adds.



The last time scientists met like this was in 1975, when it became clear that the DNA from one species could be spliced into another. One experiment underway at the time aimed to put DNA from a cancer-causing monkey virus into bacteria that infect humans. The potential for disaster led to a meeting in Asilomar, California, to agree and make public fresh safeguards for the experiments.



Jennifer Doudna, an inventor of a gene editing tool called Crispr-Cas9, said Asilomar was much in mind when the summit was organised. “I think it’s this generation’s version of Asilomar,” she says. “It’s a very exciting time, but as with any powerful technology, there is always the risk that something will be done either intentionally or unintentionally that somehow has ill effects.”



In many countries, the UK included, it is illegal to genetically modify a human embryo that is destined to become a person. Known as germline modification, the procedure is fraught with dilemmas. Tweak the DNA of an embryo and the changes appear in every cell in the adult body. That includes sperm and eggs, so the genetic changes, and any unexpected side-effects, are passed down to future generations.



Among the scientists attending the meeting are many who are reluctant to say never to the genetic modification of embryos. The procedure could prevent devastating genetic disorders such as Tay-Sachs from being passed on, they argue. Futuristically, embryos could be engineered to resist disease, or have genes that increase the risk of cancer and dementia removed.



“I don’t want to be drawing red lines at this stage,” says Sir John Skehel, who will represent the Royal Society. Cicerone says he wants to hear from patient groups before making his mind up. For Doudna, who has called for a moratorium in the past, it is “premature and probably not practical to draw a red line”, but says far too little is known about safety and effectiveness to consider it today.



Scientists have invented a suite of tools to edit DNA, but the most popular is Crispr-Cas9. It works like the find and replace function on a word processor, first locating the gene to be edited, then making the necessary change. It has been put to a bewildering range of uses: re-creating genetic diseases in animals, making hardier crops, designing human cells that are resistant to HIV, and creating genetically modified (GM) mosquitoes that cannot spread malaria. In April, a Chinese team reported the first attempt with Crispr-Cas9 to edit the DNA of human embryos to correct genetic faults behind a rare but often fatal blood disorder called beta thalassemia. In September, a British research group applied for permission to edit human embryos for research purposes. In the UK, donated embryos can be studied for 14 days and then destroyed.



Marcy Darnovsky, director of the Center for Genetics and Society, and a speaker at the summit, said that the meeting could make a real contribution to the debate, but needed to be far more inclusive. “What is unsettling is that the organisers are from the three areas of the world where there seems to be, among scientists at least, the most enthusiasm for going forward.”



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Darnovsky wants a total ban on editing human embryos that are destined to become people. “It’s way too risky and it’s likely to remain that way,” she says. If editing was allowed to prevent diseases being passed on, it would quickly lead to designer babies, she argues. “People say it is a slippery slope. I don’t call that a slippery slope, I call that jumping off a cliff,” she says. “We would be well on the way to a world in which people who could afford to do so would attempt to give their children the best start in life, and competitive and commercial pressures would kick in. We’d end up in a world of genetic haves and have-nots, and risk introducing new kinds of inequality when we already have shamefully way too much.”



Another speaker, Hille Haker, a Catholic theologian at Loyola University in Chicago, wants a temporary ban on editing human embryos for basic research, and “strict prohibition” on any work that leads to GM embryos being implanted in women. Her objection is not anchored in the sanctity of human life. She fears that women and their babies would be subject to intense monitoring by scientists, until the children are adults. That burden is unacceptable, she argues. The simplest remedy for a couple who are bound to pass on a genetic disease is to use sperm donation and pre-implantation diagnosis to select healthy IVF embryos, she says. The desire to have genetically related children should not be a trump card, she argues.



Cicerone says the meeting may not reach a consensus, but hopes for some agreement in key areas, such as what is beneficial for society. As with stem cell research, different countries may come to different conclusions, he says. “These are complex questions,” he says. “It may take further meetings.”

