Before there was CRISPR, aspiring genome editors relied on an island of misfit, less elegantly named enzymes: Zinc-finger nucleases, TALENs, recombinases.
Many of these once beloved tools were tossed aside when CRISPR came along, having helped few actual patients but driven plenty of graduate students to exhaustion. They were stubborn, inflexible enzymes, requiring endless engineering. CRISPR, by contrast, lets you cut almost any stretch of DNA with a simple chemical code.