"Before you read this paper"

Genetic dissection, whereby a specific biological pathway is interrogated by comprehensive mutant analysis, is now widely used in various contexts in various organisms. 50 years ago, however, biologists did not know to what extent complex functions of plants and animals, such as development and behavior, are under the control of genes. The pioneering work by Nusslein-Volhard and Wieschaus in 1980 was the first to apply genetic dissection to a problem in developmental biology. They systematically screened for mutants defective in embryonic segmentation, an important event that occurs early in fly development. Their screening was not only successful in that they obtained many mutants: more importantly, the unique phenotypes of individual mutants revealed the existence of previously unrecognized mechanisms underlying segmentation. Another surprise followed when it was discovered that the homologs of these genes also play similar roles in vertebrate development. In the lecture, we will discuss what we can learn from genetic dissection and how this paper inaugurated the era of developmental genetics.