"Eyeless" gene (Pax 6) Quotes in Your Inner Fish
Gehring's lab found they could use the mouse gene to trigger the formation of an extra fly eye anywhere: on the back, on a wing, near the mouth. What Gehring had found was a master switch for eye development that was virtually the same in a mouse and a fly. This gene, Pax 6, initiated a complex chain reaction of gene activity that ultimately led to a new fly eye.
Jellyfish do not have either Pax 6 or Pax 2: they arose before those genes hit the scene. But in the box jellyfish's genes we see something remarkable. The gene that forms the eyes is not Pax 6, as we'd expect, but a sort of mosaic that has the structure of both Pax 6 and Pax 2. In other words, this gene looks like a primitive version of other animals' Pax 6 and Pax 2.