Two decades ago, I sat at Herman J. Muller's desk at Indiana University, pushing flies as he once did. Looking back in light of the recent unveiling of the Drosophila melanogaster genome sequence,1 I realize that I was struggling in the Dark Ages of genetics, when we worked by inference rather than scanning databases of A,T, C, and G. If I labored in the Dark Ages, then Thomas Kaufman, my mentor, received his training in the Stone Age; Muller was positively Precambrian.
Back in the 1970s, we would routinely drive fly larvae to a children's cancer treatment center in Indianapolis to zap them with X-rays, or we'd expose larvae to chemical mutagens. Weeks later, we'd scrutinize the next generation for the errant bristle pattern or missing, extra, or misplaced part that would indicate mutation, the only way we had then to reveal normal function. Further matings would...