ABSTRACT
A brilliantly designed program of research was relentlessly pursued in Germany in the 1980s by Christiane Nilsslein-Volhard and Eric Wieschaus. They initiated the discovery in precise molecular detail of how differences in gene activity between the nuclei of the Drosophila embryo first arise. For this work, they were awarded the Nobel Prize in 1995. The fact that nuclei in the early Drosophila embryo are not separated by cell membranes once made studies of its early development appear somewhat irrelevant to that of other organisms, but it turned out to be a blessing in disguise. In Drosophila, mutations can be induced by shining x-rays on flies or by feeding them certain chemicals. Some mutations in Drosophila change the structure of the embryo and larva along the dorsal-ventral axis at right angles to the anterior-posterior axis. The nucleotide sequences of homeotic genes showed that they all code for protein transcription factors.
