He got his doctoral degree at the same school, in 1953 and soon afterwards went abroad on a scholarship for post-doctoral studies at Columbia University, in New York City, from 1953 to 1955.
His teaching and research professional career began in 1942, when he accepted a position of assistant professor at the School of Philosophy, Sciences and Letters of the Federal University of Rio de Janeiro, a post he held until 1958.
As a scientific leader, Dr. Frota-Pessoa held many prominent positions, such as: specialist in Science Education of the Pan American Union (Organization of American States) in Washington, D.C. (1955–1956), consultant in Human Genetics for the World Health Organization (1961–1986), director of the Coordination Center of Brazil of the Multinational Program of Genetics of the Pan American Union (1968–1973), director of the Centro de Estudos sobre Currículo para o Ensino de Biologia (CECEB) from 1972 to 1979, president of the Brazilian Society of Genetics (1968–1970) and of the Latin American Association of Genetics (1969–1971), founding member of the Academy of Sciences of the State of São Paulo (1974).
He actually taught science and biology in secondary schools of the public system of Rio de Janeiro from 1939 to 1958.
Based on this experience, he wrote one of the first textbooks on biology for secondary education, which became a best-seller and was published in many editions.