Hox gene

Hox genes are a group of related genes that determine the basic structure and orientation of animals and plants.^[1][2] 'Hox' is short for 'homeobox'.

Hox genes are critical for the proper placement of segment structures of animals during early embryonic development (e.g. legs, antennae, and wings in fruit flies or the different vertebrate ribs in humans).^[3]

Hox genes are a complex of genes whose proteins bind to the regulatory regions of target genes. The target genes then activate or repress cell processes to direct the final development of the organism.^[4][5]

• Hox genes have a DNA sequence known as the homeobox. The homeobox is a 180 nucleotide-long DNA sequence which codes for a 60 amino acid-long protein domain known as the homeodomain. This works by binding with DNA.
• Hox genes are in gene clusters on the genome
• The order of the loci in the chromosome parallels the order in which the loci are expressed in segments along the body.^[6]
• This cluster of master control genes programs the development of all higher organisms.^[7][8]
• The cluster is highly "conserved". It has not changed much over hundreds of millions of years of evolutionary history. Molecular evidence shows that some limited number of hox genes have existed in the Cnidaria since before the earliest true Bilatera. This means the system evolved before the Palaeozoic era. ^[9]

1. ↑ Dictionary.com – Hox gene [1]. Accessed March 31, 2011.
2. ↑ Jongmin Nam, Claude W. dePamphilis, Hong Ma, Masatoshi Nei. Antiquity and evolution of the MADS-Box gene family controlling flower development in plants. [2]
3. ↑ Gehring, Walter J. 1998. Master control genes in development and evolution. the homeobox story. Yale University Press, New Haven CT.
4. ↑ Lewis E.B. 1995. The bithorax complex: the first fifty years. Nobel Prize lecture. Repr. in Ringertz N. (ed) 1997. Nobel lectures, Physiology or Medicine. World Scientific, Singapore.
5. ↑ Lawrence P. 1992. The making of a fly. Blackwell, Oxford.
6. ↑ Carroll S.B. (1995). "Homeotic genes and the evolution of arthropods and chordates". Nature. 376 (6540): 479–85. Bibcode:1995Natur.376..479C. doi:10.1038/376479a0. PMID 7637779. S2CID 4230019.
7. ↑ Duncan I. 1987. The bithorax complex. Ann. Rev. Genetics 21, 285–319.
8. ↑ Cite error: The named reference clusters was used but no text was provided for refs named (see the help page).
9. ↑ Ryan J.F. et al 2007. Pre-bilaterian origins of the hox cluster and the hox code: evidence from the sea anemone, Nematostella vectensis. PLoS ONE 2, (1), e153. [3]