Scientists are puzzled by a gene that causes three out of four female Mormon swallowtail butterflies to imitate poisonous butterfly species while leaving 25 percent of females and all males vulnerable to predators.

While researchers suspect a "super gene," they haven't been able to figure out why their male counterparts and one out of four females have a harmless-looking pattern that makes them more likely to be eaten, the Los Angeles Times reported.

"They figured that this is a cluster of tightly linked genes, and each individual gene was doing some sub-set of that color pattern, but they were so close together that they would all be inherited as a single unit," University of Chicago evolutionary biologist Marcus R. Kronforst, a long-time butterfly researcher, told the L.A. Times. "That's where the name 'super gene' came from. They just couldn't imagine that a single gene could do all this."

Of the Papilio polytes butterflies, 75 percent of the females have warning patterns that are "parasitic" mimicry to keep them from being eaten.

Kronforst attempted to map out the gene that results in the mimicry by mating butterflies with different patterns and working with around 500 offspring, but he was surprised by the result. Contrary to the earlier theory, the common Mormon butterfly doesn't have the same cluster of linked genes that influence the patterns.

"It's not on the sex chromosomes," said Kronforst, as reported by the L.A. Times. "It reads a message from the sex chromosomes and then it forms two different types of proteins. There's a male type of protein and a female type of protein, and that's what tells the other cells in the body: you are male and you are female."

The doublesex gene has around 1,000 mutations of its base pairs. The trait for the non-imitating pattern is mysteriously persisting in the butterfly species even though it makes them more vulnerable.

"It's possible that this gene is doing lots of other stuff," Krunforst said.

For now, the butterfly's varying patterns will remain a mystery.

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