For Fruit Flies, Turning Off a Gene Means Turning On the Same-Sex Love

By Andrew Moseman | May 27, 2008 1:09 pm

Drosophila melanogaster, the common fruit flyForget looking for a “gay gene”: fruit flies, the favorite insects of geneticists for a century, need a particular gene to keep the males straight.

A team of scientists led by Manyuan Long at the University of Chicago call it the sphinx gene, and it is present only in fruit flies. Long’s grad student Wen Wang identified the gene back in 2002, and now two other former students, Hongzheng Dai and Ying Chen, have discovered its purpose. When Dai and Chen turned off the gene, the males looked and acted ordinary, at least until they were placed in each other’s company. When that happened, the genetically engineered flies spent 10 times more time pursuing other males than normal fruit flies. Long says that the gene evolved about two million years ago to prevent male flies from inhibiting mating by spending too much time with each other.

Dai and Chen’s study is the latest in a series of experiments at different universities fiddling with fly sexual orientation. And the same-sex courtship that the fruit flies displayed was no quickie, either—the flies progressed through the full elaborate ritual they would normally use to woo a female, except they cut it short before copulation.

Ultimately, though, the genetically engineered flies grew frustrated with their failed attempts to get it on, and returned to the females. The sphinx gene is dormant in female fruit flies; as such, they’re only affected by lack of male attention.

Image: André Karwath © 2005

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  • Kristen

    Could a long dormant gene in women today have become activated by some environmental pollutant or combination of pollutants? Like the movie wit Lily Tomlin from the 80’s “The Incredible Shrinking Woman”, perhaps all these chemical cocktails we are exposed to are having an effect on us genetically.

    I recall the study with the frogs that became homosexual in behavior after sitting in a specific chemical. This is important stuff. Many people wish they could control this aspect of their lives. Wouldn’t it be great if they could? It would still be their choice, but at least the choice of which gender they are attracted to would not be left up to chance. Environmental toxins are polluting our water, air and food supplies. More studies would help isolate those toxins that are affecting gender identity issues. Hope to hear more about this in days to come. Thanks to the students who isolated this gene for male fruit flies, there is hope that more studies can produce similar results in other species.

  • bella

    This makes sense as 1. We all evolved from asexual organisms and 2. Heterosexuality was the genetic enhancement it is the mutation toward improvement so it makes sense that it’s the heterosexual gene that has become switched off or damaged in these people.  


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