Pax genes are important when an animal is developing specific tissues because it acts as a master control gene for development of eyes and other sensory organs. This gene is highly conserved across species which indicates its importance in the development of eyes in the animal kingdom. A mutation in this gene can lead to the absence of eyes or deformed eyes. The eyeless gene makes a protein that is a transcription factor, and when this protein expresses, it binds to a specific set of genes initiating the formation of eyes. It is interesting that when observing the genetic makeup of invertebrates like fruit flies, to vertebrates, such as humans, the genes for the formation of eyes are highly conserved over time, because they are master control genes important in the initiation of sensory organ formation.