Hox genes are found in the genomes of all animals, and play a fundamental role in shaping the animal's body and appendages. as this diagram shows, hox genes exhibit a high degree of homology among organisms. in the diagram, the structures formed in adult drosophila (top of the diagram) and in an early human embryo (bottom of the diagram) are depicted by colors along the anterior-posterior axis corresponding to the members of the hox cluster that control their formation. the order of the hox genes along the body is similar between fruit flies and humans.