Imagine if you had to rectify every spelling mistake in an article by adding a copy of the full corrected sentence at a random point. Well, that's pretty much how gene therapy and genetic engineering work right now. Instead of editing individual letters of the DNA code, you have to add a whole new piece of DNA, and there's no way to control where it ends up. More precise gene therapy has cured the immune system of about 20 boys.
Other genetic engineering techniques were performed on a basset hound