After spending two years at Galton Laboratory in London under the supervision of Lionel Penrose, Alfonso León de Garay founded the Genetics and Radiobiology Program (GRP) in 1960 within the National Commission of Nuclear Energy (CNEN) which has been founded in 1956. The Program rapidly became a disciplinary program, for it embraced research, teaching, and training of academics and technicians in radiobiology and genetics. The Program with its laboratories started in 1960, located in an apartment building in México City. At the beginning it consisted of a small staff composed of six researchers, including de Garay as director, Rodolfo Félix Estrada as chief of the Drosophila section, and 4 investigators who had all obtained their B.A. degrees in Biology in 1960. There was also a technician, a secretary, and a service assistant. By 1960 de Garay obtained 22 Drosophila mutants that were used to know the mutational effects of radiation sources with tracing isotopes. To obtain these mutants, and as part of the personnel training, there were organized annual course works about radioisotopes and nuclear instrumentation. Those course works were compulsory for the personnel who work in the Program. By 1962 de Garay and collaborators obtained 57 Drosophila mutants that were used for research and educational purposes. In this paper I will talk about the creation of the CNEN and the institutional need of creating a program to study the effects of radiation in human populations in Mexico. De Garay's role in the development and establishment of radiobiology and human genetics in Mexico was fundamental.