Gene editing
An illustration of CRISPR-CAS9 gene editing complex from Streptococcus pyogenes. Getty Images

Researchers at the Oregon Health and Science University (OHSU) in Portland have carried out the first known attempt at creating genetically modified human embryos in the United States.

According to MIT Technology Review, the DNA of a large number of one-cell embryos was changed with the gene editing technique CRISPR.

The technique, which has the ability to permanently modify genes in organisms, can selectively trim away parts of the genome that is deemed unwanted to replace it with new stretches of DNA.

However, the edited embryos were not allowed to develop for more than a few days and were never intended to be implanted in any womb.

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The report said the three previous instances of editing human embryos were all published by scientists in China. This was the first time this was achieved in the U.S. through the research, led by Shoukhrat Mitalipov, head of OHSU's Center for Embryonic Cell and Gene Therapy.

The study has 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.

However, research in the field of genetic modifications of human embryos has always been deemed controversial.

In the International Summit on Human Gene Editing held in 2015 in Washington D.C., scientists debated the safety risks and ethical hazards of modifying the human embryos and human "germline" (the genetic blueprint that will be passed on to future generations) using CRISPR. They said although basic and preclinical research should be allowed, edited human embryos should not be used to establish a pregnancy.

They also said It would be "irresponsible" to edit the human germline, until the safety issues had been resolved. "The concept of altering the human germline in embryos for clinical purposes has been debated over many years from many different perspectives, and has been viewed almost universally as a line that should not be crossed,” Dr Francis Collins, director of the National Institutes of Health said in April 2015. The NIH also does not fund any use of gene-editing technologies in human embryos.

Scientists have even questioned the ethics of genetically editing human embryos, saying that gene-editing technology could be used to create designer babies with enhanced traits, such as higher intelligence or greater beauty.

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There are also many who are enthusiastic about the idea. In a report this year, National Academy of Sciences (NAS) and the National Academy of Medicine said scientific advances made gene editing in human reproductive cells "a realistic possibility that deserves serious consideration.”

For many, one of the most important reasons behind editing human embryos is that it has the potential to prevent genetic diseases like cystic fibrosis or Huntington's disease, which are caused by mutations in a single gene and could be fixed using CRISPR.

A popular consensus is also that it could be permitted in the future, but only for serious conditions under stringent oversight.