In a first, scientists precisely edit human embryo genes

Scientists at Columbia University have edited the DNA of early human embryos with unprecedented accuracy, an achievement that could open the way to babies engineered with particular characteristics.

The prospect has fuelled controversy for years. On the one hand, the technology might one day enable parents to safely repair disease-causing mutations in embryos. But it might also be used to select desired traits – a practice that some ethicists have argued is nothing short of eugenics.