Octopuses, squid, and cuttlefish often do not follow the genetic instructions in their DNA to the letter. Instead, they use enzymes to pluck out specific adenosine RNA bases (some of As, out of the As, Ts, Gs, and Us of RNA) that codes for proteins and replace them with a different base, called Inosine. This process—called “RNA editing”—is rarely used to recode proteins in most animals, but octopuses and their kin edit RNA base pairs in over half of their transcribed genes. When researchers did experiments to quantify and characterize the extent of this RNA editing across cephalopod species, they found evidence that this genetic strategy has profoundly constrained evolution of the cephalopod genome. The study appears in Cell on April 6.