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Homeobox genes, often abbreviated as Hox genes, are a conserved family of genes found in most animals. They play a crucial role in the development and organization of the body plan during embryonic stages. Specifically, Hox genes are known as transcription factors, meaning they regulate the expression of other genes. Their primary function is to determine the identity of different body segments along the anterior-posterior (head-to-tail) axis.

The name "homeobox" comes from the "homeobox" sequence, a highly conserved DNA sequence of about 180 base pairs that is present within these genes. This sequence encodes a protein domain called the homeodomain, which is responsible for binding to DNA. The spatial and temporal expression patterns of Hox genes are critical; they are typically arranged in clusters on chromosomes, and their order within the cluster often corresponds to their order of expression along the body axis, a phenomenon known as colinearity.

Mutations in Hox genes can lead to significant developmental abnormalities, such as the transformation of one body part into another. For example, a mutation might cause legs to grow where antennae should be. This highlights their fundamental importance in establishing the correct pattern of body structures. The study of Hox genes has provided profound insights into the genetic basis of animal development and evolution.