A gene is the basic package of genetic instructions that tells cells how to build some protein. Proteins are the chemicals that do much of the work of cells. Gene drives are pieces of DNA that have been tweaked by scientists. These snippets of DNA have been designed to find a target gene, slice into it and then insert themselves. This cut-and-paste system alters the function of the original gene. And it is self-propagating, which means that it makes more of itself.