Medicine: Mighty Mice

Gene transfers create giants

It was the sort of biological alchemy that abounds in science fiction. Take a trait from one species, genetically transfer it to another species, and voilá!: a hybrid emerges that nature could never have produced. In last week's issue of the British journal Nature, scientists at four American institutions announced that they had actually accomplished this remarkable, first-of-its-kind feat. A gene carrying the DNA code for growth hormone was taken from rats and incorporated into mouse embryos. The result: mice that grew to be nearly twice the normal size. The super-mice not only produced large quantities of rat...