An experienced fruit fly researcher can tell at a glance whether the fly she is observing is male or female; a distinct pigmentation pattern on a fly's body (a type of bristle found only on the legs of males) and differences in the genitalia are dead giveaways. But most of the fly's body parts look identical in males and females, and until now, scientists had no idea whether "maleness" or "femaleness" extended to all of the insect's cells and tissues. In a study publishing today in the online, open access journal PLoS Biology, researchers at the Janelia Farm Research Campus of the Howard Hughes Medical Institute find that most cells in flies' bodies are identical, regardless of whether they are in a male or a female.
This is because the influence of sex-determining genes is restricted to specific tissues, says Bruce Baker, a group leader who conducted the research with colleagues Carmen Robinett, Alex Vaughan, and Jon Michael Knapp. Baker has been studying the genetics of fruit fly sex for 30 years. By the early 1980s, it was known that a cascade of genes determines how tissues and organs develop in a sex-specific manner. In this bureaucratic chain of command, each gene tells the next one how and when to act. The doublesex gene, the master gene that determines sexual characteristics, is the last gene in the cascade. In flies, females express one form of doublesex, and males another. This gene is viewed as a master switch that tells female cells to create female sexual characteristics and male cells to make male ones. Until now, fly geneticists clung to the notion that the male version of doublesex was switched on in every cell of male flies, while the female version was present in every cell in female flies.
Prompted by other labs reporting that doublesex is turned on only in small areas in the fly embryo and only in specific parts of the brain, Robinett and her colleagues employed a genetic engineering technique to detect doublesex ex
|Contact: Jennifer Michalowski|
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