The End of the Beginning

The sequencing of the complete genome of the fruit fly Drosophila ( Adams et al ., Myers et al ., Rubin et al .) is a remarkable feat that tells us much about the organization of the genomes of complex creatures. In a Perspective, Brenner looks to the future, to the next big step forward, which will be deciphering what the protein product of each gene does and how each gene is switched on and off.