The Chinese government on Thursday ordered a temporary stop to all scientific research related to the editing of human genes, the latest condemnation following claims by by Chinese scientist He Jiankui that he had genetically altered twin babies.
According to He Jiankui, the goal of his work was not to prevent an inherited disease in babies, but to bestow them with a trait to resist any possible future infection with HIV.
Speaking Wednesday, Dr He, of Southern University of Science and Technology in Shenzhen, said he was "proud" of his work.
The issue of editing human DNA is extremely controversial, and only allowed in the U.S. in laboratory research - although USA scientists said previous year that they had successfully edited the genetic code of piglets to remove dormant viral infections. In a statement, the university said it was unaware of his work, emphasizing that it was not conducted on campus. The technology enables scientists to cut an arbitrary DNA sequence in genomes.
It was first announced earlier this week that Prof He had altered the DNA of embryos - twin girls - to prevent them from contracting HIV.
He said: "We have never done anything that will change the genes of the human race, and we have never done anything that will have effects that will go on through the generations".
"Right after sending her husband's sperm into her egg, an embryologist also sent in CRISPR/Cas9 protein and instructions to perform a gene surgery meant to protect the girls from future HIV infection", he said.
It's all uncharted territory, and the long-term consequences of gene editing on humans can be unpredictable, which is why the scientific community advises caution. He sought to disable a gene called CCR5 that forms a protein doorway that allows HIV, the virus that causes AIDS, to enter a cell.
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Such experiments would be illegal in the United States and many other countries.
The committee organizing the Hong Kong conference where He is due to speak - the Second International Summit on Human Genome Editing - said in a statement on Monday it had only just been informed of He's work on the genes of the twin girls. An American scientist, Michael Deem of Rice University, also worked on the project.
If it is true, the experiment is deeply controversial. The major concern is that any edits will be passed on to offspring, thus making their way into the gene pool.
If the claim is verified, genetic engineers have already likened the birth to that of the first baby born through IVF.
Professor Hawking, who predicted that humans would discover ways to "modify intelligence and instincts" in this century, warned against such genetic modification, voicing the possibility that gene engineering could give rise to a new species of human that might lead to the destruction of the rest of humanity. "The study has been submitted to a scientific journal for review", he added. National Institutes of Health director Francis Collins issued a statement that germline editing of embryos was "viewed nearly universally as a line that should not be crossed".
'First, we would have expected to see a lot more research into the safety and efficacy of genome editing in human embryos, before attempting to achieve a pregnancy, ' she said.
"This experiment exposes healthy normal children to risks of gene editing for no real necessary benefit", Savulescu said.
According to Jiankui and his colleagues, they used CRISPR to make changes in one-day old embryos in a gene called CCR5.