Hox genes (also known as homeotic genes) are a
group of related genes that control the body plan of an
embryo along the cranio-caudal (head-tail) axis. After the embryonic segments have formed, the Hox
proteins determine the type of
segment structures (e.g. legs, antennae, and wings in fruit flies or the different types of vertebrae in humans) that will form on a given segment. Hox proteins thus confer segmental identity, but do not form the actual segments themselves.