Eating behaviour in humans has always been a puzzle, but the clue to our consumption could be genetically influenced. If it is, the pesky fruit fly may provide clues to the mystery.

    York University biology professor Marla Sokolowski and Dr. Ralph Greenspan, Senior Fellow at the Neurosciences Institute in San Diego, have discovered that genetics influence the fruit fly's eating behaviour. For the first time, scientists have found out why some fruit flies stray far from home to eat, while others remain close by.

    Sokolowski and her colleague discovered that an enzyme produced by a particular fruit fly gene (dg2) told the insects how to search for food. Fruit fly populations divide into two groups: "rovers," who look abroad for food, and "sitters," who stay close to home.

    "We used genetic engineering to change the rover/sitter gene so that we could artificially increase and decrease enzyme levels, turning rovers into sitters and back into rovers again," says Sokolowski. "This proved that rover and sitter behaviours resulted from differences in the enzyme levels produced by the dg2 gene. It also showed that environmental factors alone (for example, scarce or bad quality food) can't explain these differences in fruit fly behaviour," she says.

    "Our findings are significant for humans," she says. "They show that small differences in a gene can make a big difference in the behaviour of normal individuals. It's interesting because many fruit fly genes show strong resemblances to our own genes. And versions of the gene we discovered in the fruit fly are found in our own brain."

    Sokolowski cautions that the rover/sitter gene does not solely determine whether a fly is a rover or sitter. "The dg2 gene interacts with other genes and with environmental factors to create the behaviour," she says.