Thursday, March 11, 2010

Fly away with me

Look who's on the cover of Science, Drosophila melanogaster, the "black-bellied dew lover," better known as the fruit fly that swarms annoyingly about our food trash. Shoo! Shoo! We brush them away with our hand, and still they swarm, a cloud of living confetti.

And here he is, in all his ugly glory, up close and in your face, every bristle, every crease, every facet of its compound eyes. An 8-by-10 glossy ready for the Hollywood casting agent -- "The Creature from the Black Banana," Gozilla's tiny cousin. A splendid portrait this, made with a scanning electron microscope (the eyes artificially colored).

The fruit fly was adopted as a research animal by T. H. Morgan in his important studies in genetics that began at Columbia University in the early years of the last century. These studies led to the classic textbook of Morgan, Sturtevant, Muller, and Bridges, "Mechanisms of Genetic Inheritance," which in 1915 established the link between genes and chromosomes. Since that time, much of what we know about mutation, speciation, and other genetic phenomena has been discovered with populations of fruit flies. Drosophila is an ideal research animal. It is small enough to breed in the lab in large numbers, but large enough to examine with only modest magnification. And it has a short life cycle, which means it can be bred through many generations during a typical graduate student's time of study.

The Science cover introduces work by a group of California researchers who identify proteins that inhibit age-related pathologies in fruit flies -- muscle degeneration and cardiac malfunction, among others. Does Drosophila hold the key to eternal youth? Who knows. Humans are more complex than fruit flies -- more genes, more chromosomes -- but many of our proteins and their way of functioning are virtually the same. Much of the basic biochemical machinery of human life evolved before the ancestors of fruit flies and humans diverged a half-billion years ago.

I've had the pleasure of examining mutant fruit flies, jiggered by geneticists to study the relationship between genes and their expression. The mutants have Seven Dwarfish sorts of names -- Dumpy, Curly, Stubble, Spineless, Wrinkled, Bristle, and Scarlet -- every aberrant feature determined by a sequence of four paired chemical units called nucleotides, A-T, T-A, G-C and C-G. Somehow it's all there in the four-letter code, the plan for making a fruit fly maggot, then for rearranging the maggot to make a fly, the alarm clock that causes the fly to emerge from its pupa in the dewy morning, the courtship love song, and all the rest.

Take another long look at the microphotograph above, and next time you swat, think of all the wonderful living detail that you squash between your hands.

(Image by T. Deerinck and M. Ellisman of the National Center for Microscopy and Imaging Research, University of California, San Diego.)