What is a Gene?-Twenty Years Later

Abstract

Address of the president of the American Society of Naturalists, concerned primarily with a review of work done in the author''s laboratory, and presenting a working hypothesis regarding the mutability and structure of genes. It is assumed that the action of muta-gens is indirect, through their effect on certain physiological processes of the cell which influence genes, and that each gene reacts differently to the conditions created by a mutagen. Evidence of pseudoallelism in Salmonella is presented, indicating that gene loci comprise sections of a chromosome, and that mutational changes occurring in different regions of these sections give rise to different alleles.