Gene editing technology isn't just useful for curing the world's ills, it seems. University of Chicago scientists have used the CRISPR technique to discover a key evolutionary connection between fins and hands. Researchers edited fin-related zebrafish genes to make the appropriate cells glow as they develop, and discovered that there's a similar glow in a mouse's digits. In other words, there's a strong similarity in the genes governing fins and digits -- they're both telling embryonic cells to show up at the end of an appendage.