By studying amphibians that can regenerate missing limbs, scientists have discovered that it isn't enough to activate genes that kick start the regenerative process. In fact, one of the first steps is to halt the activity of so-called jumping genes. In a new paper, researchers show that in the Mexican axolotl, jumping genes have to be shackled or they might move around in the genomes of cells in the tissue destined to become a new limb, and disrupt the process of regeneration.