 Between 1948 and 1950 , she developed a theory by which these mobile elements regulated the genes by inhibiting or modulating their action . She referred to Dissociator and Activator as " controlling units " — later , as " controlling elements " — to distinguish them from genes . She hypothesized that gene regulation could explain how complex multicellular organisms made of cells with identical genomes have cells of different function . McClintock 's discovery challenged the concept of the genome as a static set of instructions passed between generations . In 1950 , she reported her work on Ac / Ds and her ideas about gene regulation in a paper entitled " The origin and behavior of mutable loci in maize " published in the journal Proceedings of the National Academy of Sciences . In summer 1951 , when she reported her work on the origin and behavior of mutable loci in maize at the annual symposium at Cold Spring Harbor Laboratory , presenting a paper of the same name . The paper delved into the instability caused by Dc and As or just As in four genes , along with the tendency of those genes to unpredictably revert to the wild phenotype . She also identified " families " of transposons , which did not interact with one another . 
