Gene action in relation to growth and development. I. Phenotypic variability

Among the most fundamental problems in biology belongs the action of the gene. The gene, however, is elusive since no direct approach is possible: the gene can only be recognized by its effect. These effects may be used either in their final expression - the heritable characters - and then we are in the domain of classical genetics. Or we can try to infer from the final and intermediate steps of gene action what lies at the beginning of this chain. This is the approach of both the biochemist, the embryologist, and the physiologist. The successes of the biochemist in approaching the action of the gene are spectacular, such as in the analysis of biosynthesis in Neurospora.