Marcus Rhoades and Transposition

Barbara McClintock deservedly received the lion’s share of recognition for the discovery of transposition, including the 1983 award of an unshared Nobel Prize in Physiology or Medicine (Fedoroff 1994). But discoveries are punctuation marks in the discourse of science, and many voices impinge on the discoverer’s ear. McClintock studied genetics at Cornell. The Cornell genetics group was headed by R. A. Emerson. Marcus Rhoades undertook graduate work at Cornell not long after McClintock’s graduation and learned cytogenetics from her (Schwartz 1993). But more than that, Rhoades took important steps on the road to the discovery of transposition before, and quite independently of, McClintock’s final sprint. And while hindsight has a certain blinding clarity unavailable to the discoverer, there is always an intellectual framework into which a discovery fits. My purpose is to sketch that framework for the discovery of transposition, here emphasizing Rhoades’ work on the Dotted (Dt) locus of maize. The year 1998 marks the 60th anniversary of the publication of Rhoades’ paper in Genetics reporting seminal work on the properties of a gene with a transposon insertion, carried out a decade before McClintock’s identification of the transposable Dissociation (Ds) locus in maize.