Homeodomain protein of Drosophila

Developmental regulation proceeds through the sequential activation of a series of regulatory switches that in turn activate networks of other genes. Many different classes of regulatory genes share a common DNA sequence known as the homeobox, which predates the origin of animals. The best-studied class of homeobox-containing genes are the Hox genes, usually found clustered next to each other along animal chromosomes. A homeobox is a DNA sequence found within genes that are involved in the regulation of development (morphogenesis) of animals, fungi and plants. Genes that have a homeobox are called homeobox genes and form the homeobox gene family. In eukaryotes, a homeobox encodes a protein domain (the homeodomain) which can bind DNA that act as part of transcription factors to switch on cascades of other genes that induce cellular differentiation by initiating the cascades of coregulated genes required to make individual tissues, organs , or body parts. The image above shows a digital rendering of the Antennapedia homeodomain protein from the fruit fly (Drosophila melanogaster) bound to a DNA fragment.