Reading genetic  sequences have now become routine. Genetic information can be edited by  a new technology quickly and economically. It is called CRISPR-Cas9 or just CRISPR. Here a piece of RNA is taken to target a section of DNA. An enzyme called a nuclease, can cut out unwanted genes, and paste new ones. There are already other methods of editing genes, but CRISPR is the simplest, speediest and precise. It can be used therapeutically and to make designer babies, if genomes of human embryos are edited. Scientists for ethical reasons want to restrict the editing of  ‘germ line’  cells. It may take a generation to ensure that the technology is safe.