page_title: Homeobox
section_title: Discovery
hierarchical_section_title: Homeobox / Discovery
caption_attribution_description: Français&#160;: Mutation Antennapedia
context_page_description: A homeobox is a DNA sequence, around 180 base pairs long, found within genes that are involved in the regulation of patterns of anatomical development in animals, fungi, plants, and numerous single cell eukaryotes. Homeobox genes encode homeodomain protein products that are transcription factors sharing a characteristic protein fold structure that binds DNA to regulate expression of target genes. Homeodomain proteins regulate gene expression and cell differentiation during early embryonic development, thus mutations in homeobox genes can cause developmental disorders.
  Homeosis is a term coined by William Bateson to describe the outright replacement of a discrete body part with another body part, e.g. antennapedia—replacement of the antenna on the head of a fruit fly with legs. The "homeo-" prefix in the words "homeobox" and "homeodomain" stems from this mutational phenotype, which is frequently observed when these genes are mutated in animals. The homeobox domain was first identified in a number of Drosophila homeotic and segmentation proteins, but is now known to be well-conserved in many other animals, including vertebrates.
context_section_description: The existence of homeobox genes was first discovered in Drosophila by isolating the gene responsible for a homeotic transformation where legs grow from the head instead of the expected antennae. Walter Gehring identified a gene called antennapedia that caused this homeotic phenotype. Analysis of antennapedia revealed that this gene contained a 180 base pair sequence that encoded a DNA binding domain, which Gehring termed the "homeobox". The existence of additional Drosophila genes containing the antennapedia homeobox sequence was independently reported by Ernst Hafen, Michael Levine, William McGinnis, and Walter Jakob Gehring of the University of Basel in Switzerland and Matthew P. Scott and Amy Weiner of Indiana University in Bloomington in 1984. Isolation of homologous genes by Edward de Robertis and William McGinnis revealed that numerous genes from a variety of species contained the homeobox. Subsequent phylogenetic studies detailing the evolutionary relationship between homeobox-containing genes showed that these genes are present in all bilaterian animals.
caption: Drosophila with the antennapedia mutant phenotype exhibit homeotic transformation of the antennae into leg-like structures on the head.
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