In mid-April, researchers announced they had used a promising new gene-splicing technique to “edit out” of living human embryos the genes that could cause inherited conditions such as cystic fibrosis and hemophilia. The test was conducted in China.
The technique is called CRISPR, short for “clustered regularly inter-spaced short palindromic repeats.” CRISPR uses inert, repeating snippets of DNA to elbow aside defective genes that can cause illnesses and cast them out of a genome.
Scientists are cautiously encouraged because, unlike current methods, CRISPR can replace several different forms of defective DNA sequences in a single procedure. This makes CRISPR effective against complex diseases caused by the collaboration of more than one defective gene.
But there’s a long way to go. In the Chinese experiment, the genomes of 54 of the 71 embryos used were analyzed. Only 28 were edited; a much smaller number were edited in the way that researchers had intended.