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Pax-6 and the appearance of the eyes

As we all know, the eyes are organs that allow us to detect light, which is absolutely essential for many organisms. However, in biology classes as we just explained how the human eye (assuming no others). The reality is that there are many different solutions to see (and if not expected, the human eye is not the best). Here are some types of eyes distributed in nature:

With so many eyes, some on camera and other compounds (such as fly's eyes), one might think that must have appeared so completely independent and that the genes' builders eyes "of a fly short of a mouse or an octopus. However, this is not true. Quite the contrary, there is a master builder of an eye, called Pax-6, a highly conserved homeotic gene (more We'll talk about homeotic genes).

Such is the level of conservation of this gene, if one takes a Pax-6 in a mouse or a squid and run it in a fruit fly (Drosophila melanogaster ) that can not use its own gene, are generated fly's eyes! (Go back and read this again to size it!). Also, if one expresses this gene ectopically in the legs of a fly eye on its legs generate . The same goes for a frog, we ectopically generated lenses. This is because Pax-6, as several other genes are master keys, ie the first switch is switched on it says "build an eye here." Thus, under his command are all eye specific genes of each species. It must be said that this gene is present with great conservation in mammals, amphibians, amphioxus (a cousin of vertebrates), sea urchins, squid, worms, etc.
What explains this? Drawing on the theory of evolution is very simple to explain and predict: The common descent. A very distant common ancestor this gene had worked so well that simply was distributed around as that the species diverged from each other. But what is known ancestor was? The answer is yes, is the ancestor Urbilateria, an animal that gave rise to two major groups, the protostomes (worms, mollusks and spiders, among others) and deuterostomes (sea urchins, starfish, vertebrates and of course us)

Urbilateria The ancestor is in the second paragraph of this phylogenetic tree marking

This not only happens with the eyes, about many structures that at first glance look totally different, but that when we reduce it to genes, we began to speak a common language. That language is the evolution.