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A CRISPR first: editing normal human embryos

In the first ever report of the CRISPR-Cas9 genome-editing tool being used on normal human embryos, a team of Chinese scientists had mixed results, New Scientist writes. The team first created embryos with genetic mutations that caused two different diseases: β-thalassemia and favism (an anemia caused by eating fava beans). When they tried correcting the mutations using CRISPR-Cas9, their success rate was one in four for β-thalassemia and two in two for favism, they report this month in Molecular Genetics and Genomics. That’s better than the 10% success rate for genetically abnormal embryos, but far more work needs to be done before the technique is ready for prime time, say other scientists.