WHAT DID THE CHI­NESE SCI­EN­TIST DO?

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in a way that pa­tients would pass to their own chil­dren.

The re­searcher said he used the gene-edit­ing tool CRISPR to al­ter a gene named CCR5 in em­bryos for seven cou­ples dur­ing their fer­til­ity treat­ments; one preg­nancy re­sulted. A par­tic­u­lar mu­ta­tion in that CCR5 gene is thought to con­fer some re­sis­tance to HIV by mak­ing it harder for that virus to en­ter cells.

To­day’s med­i­ca­tions have turned HIV from a death sen­tence into a man­age­able dis­ease in much of the world, but He said he chose that gene be­cause HIV re­mains a big prob­lem in China.

But He’s claims have not been ver­i­fied by out­side sci­en­tists, and there are ques­tions about how the work was con­ducted.

WHY IS MON­DAY’S NEWS SO CON­TRO­VER­SIAL?

Al­ter­ing genes in sperm, eggs or em­bryos means those changes can be passed down to fu­ture gen­er­a­tions — peo­ple who would have no way to con­sent to those changes. Plus, long-term neg­a­tive ef­fects might not be­come ap­par­ent for years.

In 2017, the U.S. Na­tional Acad­e­mies of Sci­ence, Engi­neer­ing and Medicine said lab-only re­search to learn how to al­ter em­bryos is eth­i­cal — but said it’s not ready for preg­nan­cies yet. The academy said if it is ever al­lowed, it should be re­served to treat or pre­vent se­ri­ous dis­eases with no good al­ter­na­tives.

That lab-only re­search is go­ing on, by Mi­tal­ipov and oth­ers.

But crit­ics said Mon­day’s an­nounce­ment opens the door to “de­signer ba­bies.”

“If this goes un­chal­lenged, other rogue ac­tors will soon of­fer wealthy par­ents pur­ported ge­netic en­hance­ments for their chil­dren,” said Marcy Darnovsky of the Cen­ter for Ge­net­ics and So­ci­ety.

WHAT HAP­PENED TO THE BA­BIES?

No in­de­pen­dent out­siders know yet, which is partly why sci­en­tists are so dis­turbed.

He, the Chi­nese re­searcher, said one twin had both copies of the in­tended gene al­tered while the other had just one al­tered. Peo­ple with one copy of the mu­ta­tion can still get HIV.

Sci­en­tists who re­viewed his claims said the al­ter­ations aren’t an ex­act match to nat­u­ral CCR5 mu­ta­tions, and that a big ques­tion is whether the gene is al­tered in ev­ery cell.

The par­tic­u­lar method used is com­mon in lab re­search but not pre­cise or con­trolled enough for em­bryos, said Co­lum­bia Uni­ver­sity cell bi­ol­o­gist Di­et­rich Egli, who called it “es­sen­tially genome van­dal­ism.”

WHAT ARE THE DAN­GERS?

The big­gest con­cern: That pre­ci­sion, or lack of it. Un­in­tended mu­ta­tions could harm health rather than help it.

Where you live de­ter­mines if, or what kind of, re­search can be per­formed on hu­man em­bryos. In the U.S., sci­en­tists can per­form lab­o­ra­tory em­bryo re­search only with pri­vate fund­ing, not with fed­eral tax­payer money. Any preg­nancy at­tempt would re­quire per­mis­sion from the Food and Drug Ad­min­is­tra­tion, which is cur­rently pro­hib­ited by Congress from even re­view­ing such a re­quest — a de facto ban.

Peo­ple un­der­go­ing fer­til­ity treat­ments that in­clude IVF can have em­bryos tested for deadly gene mu­ta­tions that run in the fam­ily, such as Hunt­ing­ton’s dis­ease, and then im­plant only the em­bryos that lack such mu­ta­tions. Also, some so-called mi­to­chon­drial dis­or­ders can be ad­dressed by us­ing some ge­netic ma­te­rial from mom and some from a donor egg, along with dad’s sperm.

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