Why are scientists so upset about world's first gene-edited babies?

A Chinese scientist recently claimed he had produced the world’s first gene-edited babies, setting off a global firestorm. If true — the scientist has not yet published data that would confirm it — his actions would be a sensational breach of international scientific conventions. Although gene editing holds promise to potentially correct dangerous disease-causing mutations and treat some medical conditions, there are many safety and ethical concerns about editing human embryos.

Here are answers to some of the numerous questions swirling around this development.

What happened?
 

The scientist, He Jiankui, said he used Crispr, a gene-editing technique, to alter a gene in