noun, plural: Hox genes
The first hox gene was discovered in Drosophila. Mutation in this gene leads to the formation of a normal structure or organ in place of another at an abnormal site. For instance, mutation in antennapedia hox gene of Drosophila leads to the formation of leg in place of antenna from its head.
Eventually, other hox genes were identified in other organisms, such as in reptiles, vertebrates and plants. The first vertebrate hox gene was isolated in Xenopus by Eddy De Robertis and colleagues in 1984. In plants, one of the well known homeotic genes is the MADS-box genes.