DNA

Each of the United States' four presidential impeachment proceedings has highlighted increasingly sophisticated technologies, beginning with telegrams in the case against Andrew Johnson.

Labs are churning out more and more synthetic DNA for scientists who want to use it to reprogram cells. Some say the technology has outpaced government safety guidelines put in place a decade ago.

An international group of 18 prominent scientists and bioethicists is calling for countries around the world to impose a moratorium on the creation of babies whose genes have been altered in the lab.