This article written by Erin Garcia de Jesus discusses how one defective gene might turn some bunnies hops into handstands. It may be a result of a gene tied to limb movement. Mice with a mutation to a gene also do handstands when they start to run. Leif Andersson, a molecular geneticist at Uppsala University in Sweden, ran a study where hop-less d'Alfort male rabbits were bred with Zealand white rabbits that can hop. There seems to be less of the RORB protein in specialized nerve cells that have the mutation compared with rabbits that don't. Without the RORB proteins the rabbits could lack the ability to coordinate what their hind limbs are doing. This restricts their ability to hop.