Monday, June 16, 2008

Swimming with the tide?

Cute little fellow, this. A bdelloid rotifer, a tiny freshwater invertebrate known for its ability to survive repeated desiccation. More interesting, perhaps, is the fact that rotifers have evolved over millions of years without sex. Sex is nature's way to juggle genes, providing the variation that drives natural selection.

Now, in the May 30 issue of Science, researchers at Harvard University and the Marine Biology Lab at Woods Hole report that bdelloid rotifers have been busy scavenging genes from whatever sources they can find -- including bacteria, fungi and plants. It's called horizontal gene transfer (HGT), and may explain why bdelloid rotifers have diversified into more than 360 species over 40 million years. Many of the purloined genes appear to have retained their functionality. Variation by theft! The advantages of sex without the bother of finding and wooing a mate.

Anything rotifers can do, we can do better. Genetic engineers have mastered the art of splicing genes from one organism into the genome of another. Armies of clever HGT abettors in white coats are snipping and stitching in a horizontal frenzy. It's a development that might help humans as much as it helped the little translucent swimmer in the photo above -- but it is fraught with moral ambiguity.

It's not just a matter of moving genes around from species to species. The day is not far off -- if it's not here already -- when a genome can be designed on a computer from the ground up, gene by gene, then executed in the flesh. Few will object to the elimination of inherited diseases, or the regrowth of amputated limbs. But are we ready for designer babies? Cosmetic gene therapy? Drug-producing goats with human genes? Factories that grow chicken meat without chickens?

We are just beginning to figure out how a half-a-billion bits (or so) of DNA becomes a rotifer, and how 3 billion bits of DNA becomes a human being. If nature can do it, so can we. If we choose to.