US scientists have reported a bizarre breakthrough in genetics - the ability to grow a third eye on a scarab beetle.

Matching up cells is a major part of the scientific puzzle to regenerate limbs. Researchers at Indiana University Bloomington now say they have made a promising step in developing body parts “outside their normal context.”

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The development comes in the form of manipulating the genetic makeup of a dung beetle to give the creature a third eye at the center of its forehead. Tests on the extra eye showed it grew nerve connections and displayed the response associated with a working eye.

Published in Proceedings of the National Academy of Sciences journal, the study describes the “down-regulation” of a beetle’s head gene to produce a “functional compound eye-like structure.” Armin P Moczek, a professor in the IU Bloomington Department of Biology, told IU News the discovery centered on disrupting a specific gene called orthodenticle.

A 'three-eyed' beetle could reveal the biological mechanism behind the evolution of new traits. https://t.co/2KmVIYnbuG via @IUNewsroom — IU Graduate School (@IUgradschool) November 13, 2017

“This study experimentally disrupts the function of a single, major gene. And, in response to this disruption, the remainder of head development reorganizes itself to produce a highly complex trait in a new place: a compound eye in the middle of the head,” Moczek said.

He compared the gene-tinkering process to playing with Lego, although the creation of an additional eye appears to have been anything but child’s play. “Developmental biology is beautifully complex in part because there’s no single gene for an eye, a brain, a butterfly’s wing or a turtle’s shell,” Moczek said.

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“You can make new things over and over or in new places using the same old set of ‘bricks,’” he added. “But in Legos, we know the rules of assembly: which pieces go together and which things don’t. In biology, we still struggle to understand the respective counterparts.”

Lead author of the study, Eduardo Zattara, said the results suggest abnormal growth of eyes is a highly accessible area of study:“We regard this study as really opening the door to new avenues of investigation in multiple disciplines.”