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Fruit Fly Sexuality Controlled by Drugs and Genetic Manipulation

By Samantha A. Torrence     Dec 17, 2007 in Science
Scientists have discovered fruit flies can be turned gay or straight by the use of genetic treatments and drugs that effect sense of smell. The change can take place in the matter of hours, solidifying the claim that homosexuality is a genetic occurrence.
The fruit fly has been the subject of sexual study from the high school biology lab to the professional biology lab because of their reproductive rate. They are science's sweethearts when it comes to study of genetics. What some teachers lovingly call "DNA Replication" has morphed into studying sexuality and genetics as a whole.
The studies connecting homosexuality with genetics gained major attention in 1991. Identical twin brothers were examined and were found to show genetic similarities in sexual orientation. • 52% of identical (monozygotic) twins of homosexual men were likewise homosexual
• 22% of fraternal (dizygotic) twins were likewise homosexual
• 11% of adoptive brothers of homosexual men were likewise homosexual
In July 1993 the National Institute of Health released a study that genes found on the X chromosome can manipulate sexual orientation in males.
In 1995 Shang-Ding Zhang and Ward Odenwald, biologists at the National Institutes of Health in Bethesda, Maryland, transplanted a single gene into the flies that caused them to display homosexual behavior. In observation of the flies' activities it was found that the females grouped at the top and bottom of the test tube while the males formed an orgy like chain in the middle. Although preferring males, the flies would fertilize female eggs if no male was around which found them to be more bisexual.
Fast forward to 2005 and Barry J. Dickson and Ebru Demir of the Institute of Molecular Biotechnology found a single gene that could influence the mating habits of both male and female friends called the Fruitless protein. In the study the scientists were able to switch gender roles of male and female flies making them feminine or masculine. However, female flies with the male code were attracted to male flies with the female code, again making them bisexual.
The newest study conducted by University of Illinois at Chicago researcher David Featherstone and coworkers on fruit flies focuses on the influence of pheromones, and attraction to the opposite or the same sex. The alteration of the gene affecting the interpretation of male and female pheromones is called GB. Alteration of the GB gene made male flies "genderblind" or bisexual. GB transports the neurotransmitter glutamate to brain cells. Altering levels of glutamate change the strength of nerve cell junctions, called synapses, which play a key role in human and animal behavior.Scientists hypothesised that this was due to an overstimulated sense of sexual smell which made male pheromones no longer repulsive to other males."Based on our previous work, we reasoned that GB mutants might show homosexual behavior because their glutamatergic synapses were altered in some way," Featherstone said. "Homosexual courtship might be sort of an 'overreaction' to sexual stimuli."They attempted to influence the same results by first genetically altering synaptic strength and then simply using drugs and again by overstimulating the flies they became bisexual in both studies.
While scientists are far away from finding exactly what influences homosexuality in humans, the studies have sparked debate in the gay and the religious communities.
Mixed reaction from the gay community has had some praising the study. It is verifying what the American Psychiatric Association has by not signifying homosexuality as a psychological condition when it modified the DSM III R to the DSM IV, that homosexuality is a genetic occurrence and not a psychological one.
Other gays have expressed distaste at the study saying it was funded by religious entities so that they could find an excuse for "treatment."
Many religious entities still maintain that homosexuality is a psychological or environmental disorder. The Emo teen subculture as an example as it promotes homosexuality for shock factor.
While the debate still rages science keeps plugging away to explain the effect of genes on the animal kingdom.
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