Explaining "why" for the gay fly

` A somewhat interesting news@nature.com article...

` In the humans species, there is no known 'unusual' difference in either genes or brains of men and women who are homosexual that is different from those who are not. This, I think, can be attributed to our extreme complexity.
` However, the fruit fly, Drosophilia melonogaster, has simpler genes and a much simpler brain. It is therefore no surprise that such an unusual difference has been found in fruit flies, in relation to a gene known as 'fruitless'. And before you start thinking this might help with solving this mystery in humans, keep in mind:

Scientists caution that fly mating behaviour is very different from that of humans, as are our brains, so these results cannot be extrapolated to people. "No homologue of the fruitless gene is found in mammals and humans," points out Ken-Ichi Kimura of the Hokkaido University of Education in Iwamizawa, Japan.

` The male fruit flies which have a strong mutation in the fruitless gene will often fail to make a protein called Fru. This results in such flies failing to perform the tapping and tilting motions to attract females. Interestingly, males which only produce a little bit of Fru cause them to court both male and female flies.
` However, females who are engineered to carry the fruitless gene (which is normally specific to males) will go through the tapping and tilting routine to attract other females!

` So, how does this gene affect the structure of the fly brain? One difference is known: Flies which perform this mating ritual have a small network of neurons in the brain that other flies lack. How does this work? Apparently, the Fru protein keeps this cluster of nerve cells alive in young, developing flies - if a male does not have Fru, this cluster of cells will die. In females, on the other hand, the presence of Fru causes this cell cluster to develop intact.

"The idea that differences in a highly complex behaviour such as courtship can be caused by a small number of cells is very interesting," says Toshihiro Kitamoto, a researcher at the University of Iowa in Iowa City who has studied same-sex courtship in flies. Kimura and his co-authors speculate that the nerve network controlled by the Fru protein relays information about chemical cues that allow flies to recognize the sex of a potential mate.

` However, it is suspicious that this mechanism seems to be so simple - experts say that there could be many more subtle changes that are not yet known.

` Hmmm. I wonder if gene manipulation could be used to cause fruit flies which occasinally plague our kitchen to all become uninterested in reproductive sex and go extinct? Oh well, I guess old-fashioned sealing up fruit in bags and vacuuming up as many flies as possible works well enough...