Homeotic selector gene

The homeotic selector genes were discovered through the genetic analysis of Drosophila over 80 years ago [citation needed].

For example, the lab gene is found in the 3' position in the Antennapedia complex, and is expressed in the most anterior head region of the embryo.

At the same time, the Abd-B gene is located at the 5' position of the Bithorax complex, and expressed in the most posterior region of the embryo.

Although the significance of colinearity is still not understood, it is thought to have an important role, due to its conservation in arthropods, and vertebrates including humans.

[6] Homeotic selector genes encode regulatory DNA-binding proteins which are all related through a highly conserved DNA binding sequences called the homeobox (from which the "Hox Complex" name is derived from).

The Hox complex acts like a stamp, giving cells in each segment a long term positional value.

[2] Homologs of the Homeotic selector gene are found in a variety of species, varying from cnidarians to nematodes, to mammals.

The theory behind this evolutionary conservation stems from the belief that some common ancestor of worms, flies, and vertebrates had a single primordial homeotic selector gene, an ancestral Hox complex, that went through repeated duplication to form a series of tandem genes.

The arthropods are composed of a series of repeating body segments that can be modified in a limitless number of ways.

[6] Brachiopods: Src expression is limited to the head region in brachipods and helps in the development of feeding appendages.

[2] Every insect has six legs, one pair found on each of the three thoracic segments while other arthropods have a variable number of limbs.

Ubx and abd-A repress the expression of Distal-less, Dll, a gene responsible for the development of limbs.