The compound eye of flies divulges evolutionary secrets: analysis of fly eye development may shed light on human eye disease

The Pax6 group of genes belongs to a larger class of homeobox-containing genes, found in organisms from yeast to humans. They code for transcription factors and are distinguished by the presence of a specific DNA-binding motif (a homeodomain) that serves to regulate gene expression. The "helix-turn-helix" 3D structure of the homeodomain is the same structure that is seen in bacterial gene regulatory proteins, suggesting that this is an ancient conformation that has been conserved throughout billions of years of evolution.