Aniridia is a human condition in which the eye has no iris. The protein encoded by the gene responsible for aniridia is very nearly identical to the protein product of the fly Eyeless protein. What experiment could provide evidence that the two genes are functionally equivalent?

An Experiment to get proof that the two genes are equivalent functionally will be to introduce the aneroid mutation from the human eye with the condition into the embryos of Drosophila (small fruit flies) and look out for the formation of iris.

Explanation:

There exists a medical test called The Invitae Aniridia Test which can analyze the primary gene associated with aniridia however, in order to provide evidence that these same gene is also present in small fruit flies (a genus of flies called Drosophila) The method described in the answer above will do.