Operon model was proposed by
Operon concept was formulated by Francois Jacob and Jacques Monod at Pasteur Institute in 1961 studying lactose metabolism in Escherichia coli. Using collection of constitutive mutants, merodiploid dominance tests with F' plasmids, and diauxic growth experiments originally noted by Monod, they proposed clustered structural genes lacZYA transcribed as single polycistronic messenger from shared promoter controlled by adjacent operator and diffusible repressor encoded by distant lacI gene. Model introduced ideas of negative regulation, allosteric control, messenger RNA intermediary and coordinated regulation, revolutionizing molecular biology and earning 1965 Nobel Prize in Physiology or Medicine for paradigm shift.
Ref: Jacob and Monod 1961 Journal of Molecular Biology operon model – lac system proposed, Nobel Prize 1965.