In The Study of Gene Action, Bruce Wallace and Joseph O. Falkinham III review the nature of the problems that confronted geneticists in successive eras. New technologies, developed to solve the problems, inevitably stimulated an awareness of subtler problems that awaited still more sophisticated technologies. Although the physical nature of the gene was essentially clear by the late 1950s, the study of gene action, particularly during the development of higher organisms, is ongoing. Wallace and Falkinham explain how intimately progress has relied on technology. Initially limited to an examination of external features and subsequently to classical genetics and cytogenetic analyses, research was revolutionized by Watson and Crick's discovery of the double helix structure of DNA. The domain of genetics, scientists then understood, became inseparable from chemistry, biochemistry, and molecular biology.