SEARCH FOR A GAY GENE

Fruit flies are among the most sexually proficient creatures on earth. Their ability to produce a new generation in two weeks has made them the darlings of genetics researchers for nearly a century. Put a male fruit fly into a bottle with a female, and he doesn't waste any time before getting down to business.

So it's a bit bewildering to watch the behavior of certain fruit flies at the National Institutes of Health in Bethesda, Maryland. There, in the laboratories of biologists Ward Odenwald and Shang-Ding Zhang, strange things are happening inside the gallon-size culture jars. In some experiments, the...