The evolutionary analysis of Hox Genes is graphically illustrated in the below phylogenetic tree. As the below diagram illustrates, HOX genes are a family of regulatory genes that encode transcription factors and are essential during embryonic development. These genes are highly conserved between species such that all metazoans possess a common genetic system for embryonic patterning. A phylogenetic tree, also known as phylogeny, is a diagram that depicts the lines of evolutionary descent of different species, organisms, or genes from a common ancestor. As the below phylogenetic tree suggests, Hox genes are found in many animals, including fruit flies, mice, and humans. Mutations in human Hox genes can cause genetic disorders.