Hox genes are turned on by a cascade of regulatory genes; the proteins encoded by early genes regulate the expression of later genes. Hox genes are found in many animals, including fruit flies, mice, and humans. Mutations in human Hox genes can cause genetic disorders.

What are HOX genes and what do they do?

One group of animal genes containing homeobox sequences is specifically referred to as Hox genes. This cluster of genes is responsible for determining the general body plan, such as the number of body segments of an animal, the number and placement of appendages, and animal head-tail directionality.

How are HOX genes activated?

During embryonic development, Hox-genes give tissues their identity. ... The genes are located in a row on the chromosome: a cluster from Hox1 to Hox13. During embryonic development, the cluster is gradually activated. Hox1 is activated first, followed by Hox2, until finally Hox13 is reached.