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Imagine being able to remove a genetic mutation from an embryo so a child does not develop a devastating condition such as Huntington's disease.

Imagine modifying a gene so someone infected with HIV does not develop AIDS.

Imagine altering the genes of pigs so they can grow human organs that can be used to meet the dire need of organs for transplant.

Imagine tweaking the genes of Anopheles mosquitoes so they no longer carry the parasite the causes deadly malaria.

Those science fiction-like dreams are tantalizingly close to reality thanks to the gene-editing technology CRISPR-Cas9 (short for Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9, a reference to the gene's structure.)

CRISPR, which was initially developed to understand how bacteria defend themselves against viruses, has given scientists the ability to delete, tweak or insert genes, even in humans.

But, where there are dreams, there are potential nightmares.

What if gene-editing tools were used not only to prevent and treat diseases, but to create or to bolster specific traits – height, intelligence, strength – in the ominous way that Aldous Huxley warned of in Brave New World? It is under this backdrop that a blue-ribbon panel of the world's top scientists and bioethicists (including Françoise Baylis of Dalhousie University in Halifax) held a summit last week in Washington.

"We could be on the cusp of a new era in human history," David Baltimore, a Nobel Prize-winning biologist at the California Institute of Technology, and the group's chair, said in opening the meeting.

The panel produced a consensus statement on the responsible use of human gene editing that made three key recommendations:

Basic and preclinical research is clearly needed and should continue, with the goal of improving editing technology and improving our understanding of human embryos and germ-line cells. (Germ line is the term for eggs and sperm used by organisms to pass on genes from generation to generation.) However, the modified cells should not be used to establish a pregnancy.

Clinical use – somatic: There are many promising applications for gene editing of somatic cells – cells whose genome is not transmitted to the next generation. These new gene therapies, including treatments for some forms of cancer, should be carefully evaluated and regulated.

Clinical use – germ line: It would be irresponsible to proceed with germ-line editing in humans because there are too many unknowns.

The reality is that altering genetic sequences is already done extensively in biomedical research and it has been quite beneficial. But it is the new-found ability to target single genes and modify the genome permanently in specific individuals that poses all manner of scientific, ethical and societal quandaries.

As Dr. Baltimore said: "The overriding question is when, if ever, we would want to use gene editing to change human inheritance."

Currently, CRISPR – essentially a form of molecular scissors – is not terribly accurate. It can cut DNA the wrong way, causing as many problems as it resolves.

When scientists in China modified 86 embryos to alter the gene that causes the blood disorder thalassemia, only a handful survived and not all had the correct edits.

But that experiment, more than anything, made it urgent to have some form of guidelines.

The expert panel struck a pretty good pragmatic balance in its recommendations, highlighting that the technology has great potential but is not yet ready for prime time, and raising a number of red flags about issues that have to be considered when the technical barriers are overcome.

Genes rarely have a single function, and that can have unintended consequences; for example, the gene that causes the blood disorder sickle cell anemia also protects against infection with malaria. Once alterations are passed down to another generation, they are hard to remove. What are the ethics of modifying the genome forever? What if genetic "enhancements" are used coercively or to exacerbate social inequities?

Of course, these dire, dystopian warnings arise every time there are advances in science, and molecular biology in particular, from the crude beginnings of genetic engineering in the early 1970s through to embryonic stem cells and now gene editing.

The challenge, as always, is to capture the promise, without being frightened away, or turning a blind eye, to the perils.

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